WO2007014849A2 - Two photon or multi photon phthalocyanine based absorption material for optical data storage - Google Patents

Abstract

A non-resonant multi-photon absorption material, e.g. for optical data storage, is described wherein a photochromic effect is achieved in a defined volume by 2 photon or multi-photon absorption of a suitable phthalocyanine.

Description

Optical data storage

The present application pertains to a method of 3 dimensional optical volume addressing, useful e.g. for optical data storage, wherein a photochromic effect is achieved in a suitable phthalocyanine by 2 photon absorption, to corresponding uses and optical data storage media including bulk and multilayer material, as well as to novel phthalocyanine compounds.

JP-A-2005-029726 and JP-A-2005-037658 disclose an unresonant multi photon absorption material containing a sensitizing dye or emission color element, including some symmetrical phthalocyanines, for three-dimensional photoshaping, three-dimensional display or three- dimensional optical recording purposes.

It has been found that, surprisingly, using a certain phthalocyanine, especially an unsymmetric one selected, for example, from naphthocyanines, phthalonaphthocyanines or aza-analogues thereof, enhances the 2 photon absorption (PA) cross section by several orders of magnitude. Cross sections thus realized are, for example, of the range σ₂ ~ 10³ - 10⁴ GM (1GM = 10^~50 cm⁴ s per photon) when approaching the long-wavelength side of the first S₀ → Si (Qi) transition.

Besides the enhanced 2PA, especially in the near-infrared range (wavelengths, for example, in the range 1200 - 800 nm, especially about 1100 to about 880 nm), these compounds show further advantageous properties such as

(b) 2PA-induced switching between tautomers in the named range of wavelengths,

(c) low 1 PA in the same range, especially at the same wavelength, which enables 2PA storage in an arbitrary number of layers (e.g. up to 10000 layers, or 1 to 1000 or 2-100 layers; especially about 100 to 1000 layers).

These properties are important for a practical multi-layer optical information storage (OIS) scheme. Based on these findings of the invention, a method of writing and recording of information may comprise the following steps:

(a) preparation of the metastable tautomer (T∑form) in advance by illuminating the recording medium containing the instant phthalocyanine resonantly with Qi-band of Ti tautomer. This is preferably done at lowered temperatures, e.g. at temperatures between about 5OK and room temperature (e.g. 300K), preferably between about 7OK and 273K. For some specific applications, the process is carried out at about 75-80K, e.g. using liquid nitrogen as coolant.

(b) The bits of information ("1") are written in the bulk of the disk containing a multitude of data layers by using near-resonance two-photon excitation of T2 form (T∑→ Ti transformation). In some specific applications, one bit may be written by one non-amplified femtosecond pulse of the Ti: Sa laser, focused down to a diffraction-limited volume with a large numerical aperture objective. The non-changed voxels are considered as "0".

(c) The bits are read out with near resonant excitation and confocal scheme of collection of fluorescence (e.g. via 1 PA with a cw diode laser) of form Ti.

In a further type of application, data can be erased by

(d) illuminating the material, e.g. the whole sample, in resonance with Ti tautomer absorption, or by increasing the temperature and repeating step (1), thus realizing a rewritable, high density 3 dimensional optical data medium. While bulk data erasion on the whole disk at once has a number of advantages (e.g. high speed, low error rate), for certain applications bit-wise erasion is preferred.

When carrying out steps (b) and (c), temperature is preferably kept in the lower range as explained for step (a).

Preparation of the metastable tautomer (e.g. as in above step a) can be performed with the same laser beam used for writing and reading, e.g. if the laser wavelength is shifted to coincide with the absorption band of the stable form. This does not imply using a second 2PA laser, but may require the wavelength of the same laser to be shifted or filtered accordingly.

Data layers may be located in separated layers of the recording material, or especially in the bulk of the recording material by application of the appropriate adressing technique during writing; in the latter case, the data storage medium preferably contains only one bulk layer of the recording material. Thus, in many cases, data storage will be accomplished in a bulk material, wherein single bits are located in defined spaces of the 3-dimensional structure adressed in a 2 beam technique as previously described in literature. Layer structure and writing/reading device may also be, for example, as described in WO 99/23650. Phthalo- or naphthocyanines or aza-analogues thereof especially useful in the present invention basically consist of 4 phthalic moieties of the formula:

(Pc; R standing for H or an organic residue, where 2 vicinal R may be interconnected to form a 3-10 membered bridging group, such as a C₄-bridging group completing an annellated benzene ring), whose N- and pyrrolic bonds are linked together to form the well known azaporphyrine ring and conforming, for example, to the formula A

The groups attached at the peripheral carbon skeleton can be, for example, -CHO, -

CO-KW_radi_cai_> -CH₂OH or -COOH, or unsubstituted or substituted formyl, hydroxymethyl or carboxyl groups which may be prepared from -CHO, -CO-KW_radicai, -CH₂OH or -COOH by methods known per se. Substituted formyl or carbonyl groups are typically their acetals, oximes or hydrazones. Substituted hydroxymethyl groups are typically -CH₂-00C-KW_radicai or -CH₂-O-KWradicai- Substituted carboxyl groups are typically esters or thioesters, such as

-OO-KWradicai or -COS-KW_radicai_> each KW_radicai being any saturated, unsaturated or aromatic unsubstituted or substituted hydrocarbon radical, for example CrC_2Oalkyl, CrC₂₀cycloalkyl, CrC_2Oalkenyl, CrC₂₀cycloalkenyl, CrC_2Oalkynyl, CrC₂₀cycloalkynyl, C₆-Ci₈aryl or C₇-Ci₈aralkyl. Further substituents may be chosen in accordance with/in analogy to compounds of formula I of WO98/14520 (see pages 3/4 therein). Preferably in the above formula A, Gi, G₂, G₃, G₄, Y and Y' independently are H, OH, halogen, nitro, COOG₉, Ci-C₂₂alkyl, C_rC₂₂alkoxy, C_rC₂₂alkylthio, C₄-Ci₂cycloalkyl, C₄- Ci₂cycloalkoxy, C₄-Ci₂cycloalkylthio, aryl, aryloxy, arylthio, wherein each alkyl or alkoxy or alkylthio or aryl or aryloxy or arylthio moiety may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each aryl or aryloxy or arylthio moiety may further be substituted by alkyl or alkoxy; and wherein each alkyl or alkoxy or alkylthio moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, S, CO, COO, CONH, OCOO, OCONH, NHCONH; G₅ and G₆ indepently are H, OH, halogen, C_rCi₂alkyl, C_rCi₂alkoxy; G₉ is H, Ci-C₂₂alkyl, C₄-Ci₂cycloalkyl, wherein each alkyl may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; and wherein 2 vicinal substituents on a phenyl ring, preferably G₃, G₄, and more preferably Y, Y', optionally may be linked to form a 4-membered bridge (CH)_xNy, where x is 2 or 3 or 4, y is O or 1 or 2 and x+y =4, to form an annellated aromatic ring.

Preferred bridging group is -Xi=C(G₇)-C(G₈)=X₂-, where G₇, G₈, Xi and X₂ are as defined below for the formula I.

Preferred are compounds wherein at least 1 moiety contains 2 vicinal substituents on the phenyl ring linked to a 4-membered bridge (CH)_xN_y, where x is 2 or 3 or 4, x is O or 1 or 2 and x+y =4, to form an annellated aromatic ring (moiety Nc). Aromatic CH moieties in each unit may be substituted, the final compounds thus being of the types Pc₃Nc, Pc₂Nc₂, PcNc₃ or Nc₄. Of special technical importance are phthalonaphthocyanines of the class Pc₃Nc.

Compounds useful in the material and process of the invention are often of the formula I

wherein

Gi, G₂, G₃, G₄, Gii, Gi2, Gi₃, G_i4, G₂i, G₂₂, G₂₃ and G₂₄, independently, are H, OH, halogen, COOG₉, C_rC₂₂alkyl, C_rC₂₂alkoxy, C_rC₂₂alkylthio, C₄-Ci₂cycloalkyl, C₄-Ci₂cycloalkoxy, wherein each alkyl or alkoxy or alkylthio moiety may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy or alkylthio moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; or a vicinal pair of residues G₃ and G₄, Gi₃ and Gi₄ and/or G₂₃ and G₂₄ together form the annellating group -Xi=C(G₇)-C(G₈)=X₂- while further residues d and G₂, Gn and Gi₂, G_2i and G₂₂ attached to the same phenyl ring are as defined for G₅ and G₆ below; G₅ and G₆ indepently are H, OH, halogen, C_rCi₂alkyl, C_rCi₂alkoxy; G₇ and G₈ indepently are H, OH, halogen, COOG₉, C_rC₂₂alkyl, C_rC₂₂alkoxy, C_rC₂₂alkylthio, C₄-Ci₂cycloalkyl, C₄-Ci₂cycloalkoxy, wherein each alkyl or alkoxy or alkylthio moiety may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy or alkylthio moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; or G₇ and G₈ together with the carbon atoms they are bonding to may be bridged together to form an annellated carbocyclic 6-membered aromatic ring, which is unsubstituted or substituted by OH, halogen, COOG₉, C_rC₂₂alkyl, C_rC₂₂alkoxy, C_rC₂₂alkylthio, C₄- Ci₂cycloalkyl, C₄-Ci₂cycloalkoxy, wherein each alkyl or alkoxy or alkylthio moiety may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy or alkylthio moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; G₉ is H, CrC₂₂alkyl, C₄-Ci₂cycloalkyl, wherein each alkyl may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; Xi and X₂ indepently are CH or N.

In analogy to other azaporphyrine-type ring systems, the central protons (hydrogen atoms) may conveniently be replaced completely or partially by heavier atoms such as deuterium, or alkaline (e.g. Li, Na), or replaced completely by a suitable divalent metal ion such as Zn, Mg, Pd on treatment with the appropriate reagents such as deuterated acid or salt, usually in solution. These modified compounds are of the formulae I' or I"

wherein D stands for deuterium or an alkali atom such as Li or Na, and one of the residues D may still be unmodified hydrogen;

M is a divalent metal atom, for example selected from Mg, Zn, Pd; and all other symbols have the meaning as defined above for formula I. Preferred are, for examples, compounds of the formula I or I', or unsymmetrical (see below) compounds of the formula I".

Especially useful in the present invention are unsymmetrical compounds, i.e. generally those deviating from C₄-symmetry, especially wherein the compound deviates from C₄- and C₂- symmetry (axes perpendicular to the azaporphyrine ring system).

These compounds are thus preferred for use in 3 dimensional information storage media or recording media based on 2-photon absorption. Different tautomeric forms of these compounds may be formulated, especially with respect of the positioning of the symmetry breaking group and the bonding of the central atom(s). All these tautomeric forms are to be understood as falling under the above structures I, I' or I".

Of specific interest therefore are compounds, for example of the formula I, I', or I", wherein the vicinal substituents Gi₃ and Gi₄ are non-annellated (compound classes Pc3Nc, Pc2Nc2, PcNc3) and, independently, are selected from H, OH, halogen, COOG₉, CrC₂₂alkyl, C_r C₂₂alkoxy, CrC₂₂alkylthio, C₄-Ci₂cycloalkyl, C₄-Ci₂cycloalkoxy, wherein each alkyl or alkoxy or alkylthio moiety may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy or alkylthio moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH.

More preferred as well are compounds of the formula I, I', or I" wherein all 3 phthalyl moieties contain substituents G₃ and G₄, Gi₃ and Gi₄, G₂₃ and G₂₄, in each case together forming the annellating group -Xi=C(G₇)-C(G₈)=X₂- (compound class Nc4), while the compound deviates from C₄, especially from C₄ and C₂-symmetry as explained above; examples of such compounds are those of the formula A containing an odd number of any of the residues Gi, G₂, G₇, G₈ different from hydrogen and/or an odd number of any of Xi or X₂ different from ther rest of moieties Xi and X₂ in the compound. These compounds are a further subject of the invention, with the exception of compounds of the formula I wherein one of each of Gi or G₂, Gn or Gi₂, and G₂i or G₂₂ is Ci-d₂alkoxy while the other is hydrogen, each of G₃, G₄, G₅, G₆, Gi₃, Gi₄, G₂₃, G₂₄ is hydrogen, and G₇ and G₈ are Ci-d₂alkoxy or C_rC₂₂alkylthio or both of G₇ and G₈ are hydrogen or the bridging group -CH=CH-CH=CH-.

Preferred compounds thereof are those of formula I, I' or I" wherein at least one of G₃ and G₄, Gi₃ and Gi₄, G₂₃ and G₂₄, together form the annellating group -Xi=C(G₇)-C(G₈)=X₂- and at least one of Gi, G₂, G₅, G₆, G₇, G₈, Gn, Gi₂, G₂i, G₂₂ is different from hydrogen, or wherein Xi is nitrogen.

Halogen is chloro, bromo, fluoro or iodo, preferably chloro or bromo on aryl or heteroaryl or fluoro on alkyl.

Alkyl is, for example, Ci-d₂alkyl inter alia comprising methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, 2-methyl-butyl, n-pentyl, 2-pentyl, 3-pentyl, 2,2-dimethylpropyl, n-hexyl, heptyl, n-octyl, 1,1,3,3-tetramethylbutyl, 2-ethylhexyl, nonyl, decyl, undecyl or dodecyl.

Ci-C₂₂Alkyl is straight-chain or branched alkyl radicals, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, amyl, isoamyl or tert-amyl, heptyl, octyl, isooctyl, nonyl, decyl, undecyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl or eicosyl.

Ci -C₂₂AI kylthio is straight-chain or branched alkylthio radicals, such as methylthio, ethylthio, n-propylthio, isopropylthio, n-butylthio, sec-butylthio, tert-butylthio, amylthio, heptylthio, octyl- thio, isooctylthio, nonylthio, decylthio, undecylthio, dodecylthio, tetradecylthio, pentadecylthio, hexadecylthio, heptadecylthio, octadecylthio or eicosylthio.

C₄-Ci₂Cycloalkyl includes, for example, cyclopentyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl, cyclododecyl, and preferably cyclohexyl.

Whenever aryl is mentioned, this means mostly C₆-Ci₂aryl, preferably phenyl or naphthyl, especially phenyl. Aralkyl is usually the alkyl as defined, which is substituted by the above aryl; preferred is Cy-Cuphenylalkyl. Alk(yl)aryl is the above aryl substituted by alkyl; preferred is phenyl mono-, di- or trisubstituted by C_rC₄alkyl.

Groups which may be unsubstituted or substituted by selected radicals such as C₆-Ci₂aryl or Cs-C^cycloalkyl, like a phenyl or a cyclohexyl ring, are preferably unsubstituted or mono-, di- or tri-substituted, especially preferred are these groups unsubstituted or mono- or disubstituted.

Hydrocarbon moieties interrupted by a heterofunctional group (such as alkyl interrupted by - O- or -COO-, which includes -OCO-) denotes a moiety which can be interrupted by one or more of these groups, one group in each case being inserted, in general into one carbon- carbon bond. Hetero-hetero bonds, for example 0-0, generally do not occure (except within the functional group as specified). If an interrupted alkyl is additionally substituted, the substituents are generally not α to the heteroatom.

As known from J. Phys. Chem. A 101 , 6204 (1997), the nonsymmetrical substitution allows for rather good spectral separation of two tautomeric forms in polymer films. Furthermore, both tautomers show very strong and narrow 1 PA S₀ → Si (Qi) band in near-IR region, which provides the opportunity to use strong resonance enhancement of 2PA, when exciting in the very vicinity of this band, e.g. using a commercially available femtosecond Ti:sapphire lasers.

Thus, the invention further relates to an optical data storage medium comprising a substrate and at least one recording layer, the recording layer containing a compound of the formula I, I' or I".

Correspondingly, present invention also relates to the use of a compound as initially described as a recording dye in an optical data storage medium, and to a corresponding method of data storage.

The recording medium according to the invention, in addition to comprising the compounds of formula I, I' and/or I", may additionally comprise salts, for example ammonium chloride, pentadecylammonium chloride, sodium chloride, sodium iodide, sodium sulfate, sodium hydrogen sulfate, sodium methyl sulfate, sodium methylsulfonate, sodium tosylate, sodium acetate, sodium hexafluorophosphate, cobalt(II) acetate or cobalt(II) chloride, the ions of which may, for example, originate from the components used.

The compounds of formula I, F and/or I" may also be used in combination with the known dyes such as known in the art especially for recording media based on 2 photon absorption.

The substrate, which acts as support for the layer(s) applied thereto, is advantageously semi- transparent (T > 10%) or preferably transparent (T>90%). The support can be from 0.01 to 10 mm thick, preferably from 0.1 to 5 mm thick.

Especially in case that a multitude of recording layers is used, the thickness of each layer may range from about 0.1 to about 50 micron 1), preferably from 0.5 to 30 μm, especially from about 3 to 10 μm, e.g. about 5 such as 2 - 7 μm. The linear absorption of the recording layer is advantageously low (optical density typically below 1 , absorption preferably below 0.01 , e.g. about 10^~4 - 10^~3) at the absorption maximum (2PA). Each recording layer may comprise thinner sub-layers, such as grooves or tracks, where the recording material is present.

A protective layer can, if desired, serve also as adhesion promoter for a second substrate layer applied thereto, which is preferably from 0.1 to 5 mm thick and consists of the same material as the support substrate.

Suitable substrates are, for example, glass, minerals, ceramics and thermosetting or thermoplastic plastics. Preferred supports are glass and homo- or co-polymeric plastics. Suitable plastics are, for example, thermoplastic polycarbonates, polyamides, polyesters, polyacrylates and polymethacrylates, polyurethanes, polyolefins, polyvinyl chloride, polyvinylidene fluoride, polyimides, thermosetting polyesters and epoxy resins. The substrate can be in pure form or may also comprise customary additives, for example UV absorbers or dyes, as proposed e.g. in JP 04/167 239 to provide light-stabilisation for the recording layer. In the latter case it may be advantageous for the dye added to the support substrate to have an absorption maximum hypsochromically shifted relative to the dye of the recording layer by at least 10 nm, preferably by at least 20 nm. For a further increase in stability it is also possible, if desired, to add known stabilisers in customary amounts, for example a nickel dithiolate described in JP 04/025 493 as light stabiliser.

Further customary constituents are possible, for example other chromophores (for example those having an absorption maximum at from 300 to 1000 nm), UV absorbers and/or other stabilisers, ¹O₂-, triplet- or luminescence-quenchers, melting-point reducers, decomposition accelerators or any other additives that have already been described in optical recording media, for example film-formers.

The recording layer comprises a compound of formula I, I' and/or I" or a mixture of such compounds advantageously in an amount sufficient to provide a substantial two-photon absorption in a layer, while playing no substantial influence or at least only a low influence on the refractive index, for example from about 0.1 % to about 10% by weight, or up to 20% by weight, preferably about 1% by weight such as 0.5 to 5%, based on the total recording layer.

Due to their unique properties regarding 2 photon absorption, the present phthalocyanines may generally be used for three-dimensional (3D) volume addressing including purposes other than optical information storage, wherein these properties are useful; many examples for such applications are described in WO97/09043 or the publications initially mentioned, such as photodynamic therapy (especially cancer therapy), or 2 photon initiation of reactions (e.g. polymerization or coloration reactions, modulation of index of refraction, emission of light). Further applications wherein the effect of the invention may advantageously be exploited include the following ones: security printing - insertion of a 3D invisible image which only appears when IR lasers are used - optical effects; smart systems for tagging etc. (information storage for control and for reading); 3D microstructured phase fabrication in a stable polymer host matrix; 3D photoshaping composition; stereolithography; 3D display; optical limiting; optical memory applications; microfabrication; rational drug delivery.

General preparation procedure

Compounds of the formula A may be obtained by condensation of a suitable aromatic dicarbonitrile educt, e.g. of the formula

where G_rG₄ is as defined above, in presence of a base. Reactions are usually carried out in a solvent, which may be identical with the base. Suitable solvents are, for example, aromatic or aliphatic hydrocarbons, alcohols, ethers, or mixtures thereof. As bases may be used, for example, alcoholates such as Li-, Na-, K-alkoholates, where the alkohol may inter alia be selected from Ci-C₈hydroxyalkanes or Ci-C₈alkoxy-C₂-C₈hydroxyalkanes; further bases suitable include alkaline sulphides such as Li or Na sulphides, or non-nucleophilic amines such as DBU, DBN and the like. Reactions are often carried out in the range from room temperature to reflux temperature of the solvent or, for example, in the range 20 - 100 ⁰C. Reactions may be carried out using a protective atmosphere under normal, reduced or increased pressure, e.g. under argon or nitrogen atmosphere.

In order to obtain a certain class of asymmetric product, e.g. of the classes Pc₃Nc, Pc₃An, Nc₃An, Nc₃Pc, An₃Pc, An₃Nc, the ratio of dicarbonitrile educts major component: minor component is preferably around 9 : 1, e.g. in the range (7 - 9.5) : (3 - 0.5).

Purification and separation of isomers may be achieved by techniques commonly known such as liquid chromatography.

Compounds containing substituted aromatic rings (e.g. corresponding to formula A wherein at least one of G_rG₆and Y and Y' is different from hydrogen and at least one pair of Gi, G₂, or G₃, G₄, or G₅, G₆, or Y, Y' on the same phenyl ring are not identical) usually are obtained as mixtures of 4 isomers, one thereof conforming to the C₄-symmetry. Isomers may be separated using conventional techniques such as chromatography, or may be used as mixtures.

The following examples are for illustrative purposes only and are not to be construed to limit the instant invention in any manner whatsoever. Room temperature depicts a temperature in the range 20-25°C. Percentages are by weight unless otherwise indicated. Abbreviations used in the examples or elsewhere: M concentration in moles per litre Pc building block based on a phthalonitrile Nc building block based on a naphthalene-2,3-dicarbonitrile Ac building block based on an anthracene-2,3-dicarbonitrile NMP N-methyl-2-pyrrolidone λ_max linear absorption maximum (nm)

Preparation examples according to J. Phys. Chem. A 101 , 6204 (1997) Starting Materials 3-(2,4-Dimethyl-3-pentoxy)phthalonitrile (1), βJ-Dimethoxy-naphthalene^S-dicarbonitrile (2), and Anthracene-2,3-dicarbonitrile (3) are prepared according to the above reference.

Example 1

Pc₃Nc (4). In a 3.5 L three-necked round-bottomed flask, equipped with a stirrer, a reflux condenser, and a thermometer, are charged 1.8 L of methoxyethanol and heated under nitrogen to 50 * C. Lithium powder [19.2 g (2.7 mol)] is added in small portions within 4 h keeping the temperature at 50 ° C. 1 [60.5 g (0.25 mol)] and 4.9 g (0.0275 mol) of naphthalene-2,3-dicarbonitrile are added, and the resulting solution is heated with reflux for 18 h. The resulting green solution is cooled to room temperature, 1 L of acetic acid is added drop by drop within 1 h, and the solution is stirred for 30 min. The solution is evaporated, the residue is dissolved in CH₂CI₂, 100 g of silica gel is added, and the slurry evaporated. The green powder is placed on top of a column with 500 g of silica gel, and the symmetrical side product (R_f = 0.73) and the product (R_f = 0.57) are eluted with hexane/ethyl acetate 10:1. The fractions containing the desired product are collected, evaporated, and subjected to a second chromatography. Yield: 1.05 g (4.2%) of 4 as a green powder. TLC (hexane/ethyl acetate 10:1): R_f = 0.57. UV (NMP): JW = 757/715 nm. PD-MS (PD-MS = plasma desorption mass spectrometry): (M + H)⁺ = 907.5.

Example 2

Pc₃Nc(OCH₃)₂ (5). In the same manner, 9.2 g (38.15 mmol) of 1 and 1 g (4.19 mmol) of 2 are reacted. The crude product is purified twice with column chromatography (hexane/ethyl acetate = 7:3) to yield 0.15 g (1.5%) 5 as a green powder. TLC (hexane/ethyl acetate 7:3): R_f = 0.69. UV (NMP): ;w = 757/718 nm. PD-MS: (M + H)⁺ = 969.9.

Pc₃Nc(SC₁₂H₂₅)₂ (6). In the same manner, 21.2 g (87.50 mmol) of 1 and 5.62 g (9.71 mmol) of 6,7-dodecylthionaphthalene-2,3-dicarbonitrile¹⁵ are reacted. The crude product is purified twice with column chromatography (hexane/ethyl acetate 7:1) to yield 0.61 g (4.8%) of 6 as a green powder. TLC (hexane/ethyl acetate 7:1): R_f = 0.75. UV (NMP): A_018x = 760/724 nm. PD- MS: (M + H)⁺ = 1309.1.

Example 3 Pc₃An (7). In the same manner, 9.55 g (39.43 mmol) of 1 and 1 g (4.38 mmol) of 3 are reacted. The crude product is purified with column chromatography (hexane/ethyl acetate 7:3). The fractions containing the desired product are evaporated, and the residue is dissolved in 15 mL toluene and added drop by drop to 300 ml. of methanol. The precipitated product is isolated by filtration and dried at 60 * C/125 Torr overnight to yield 0.15 g (1.5%) 7 as a green powder. TLC (hexane/ethyl acetate 9:1): R_f = 0.49. UV (NMP): ;w = 783/735/708 nm. MALDI-MS (MALDI-MS = matrix-assisted laser desorption/ionization mass spectrometry): (M + H)⁺ = 958.8.

The chemical structure of the more stable tautomer (configuration of protons) of mixed Pc₃Nc¹S (4-7) of examples 1-3 is given by the formula:

wherein in compound: (4) R = H

(5) R = OCH₃

(7) R = -CH=CH-CH=CH-

Example 4 The following compounds are prepared according to the procedure given in example 1 from appropriately substituted benzene-, naphthalene- and/or anthracene-2,3-dicarbonitriles obtained in analogy to compounds (1), (2) or (3): Pc₃Nc (8):

( λ_max (NMP) = 753/716 nm)

Nc₄ (9):

( λ_max (NMP) = 786/750 nm)

PcNc₃ (10):

( λ_max (NMP) = 769/738 nm)

Pc₄ (H):

Pc₄ (12):

(λ_max (NMP) = 742/716 nm)

Pc₄ (13):

(λ_max (NMP) = 740/714 nm)

Pc₄ (14):

( λ_max (NMP) = 738/710 nm)

Pc₄ (15):

( λ_max (NMP) = 711/678 nm)

As noted further above, separation of isomers is achieved by column chromatography.

Compounds as described above, either in form of a selected isomer as described in example 1 , or as mixture, are used in the application experiments described further below either in solution or incorporated into a polymer film, especially a polyethylene film, which is prepared according to the method described in J. Phys. Chem. A 101, 6204 (1997).

Application example 1

Experimental Setup and Methods: Linear absorption spectra are measured with a Lambda 900 Perkin Elmer spectrophotometer. The laser system comprises a Ti: sapphire femtosecond oscillator (Coherent Mira 900) pumped by 5W CW frequencydoubled Nd:YAG laser (Coherent Verdi), and a 1-kHz repetition rate Ti:sapphire femtosecond regenerative amplifier (CPA-1000, Clark MXR). The pulses from the amplifier are down converted with an optical parametric amplifier, OPA (TOPAS, Quantronix), whose output can be continuously tuned from 1100 to 2000 nm. The OPA output pulse energy is 100 - 200 microJ (5 - 10 microJ after frequency doubling of idler), and pulse duration is 100 fs. The second harmonic of the OPA idler beam, selected from fundamental signal and idler with color filter, is used for two-photon excitation.

The excitation laser beam is slightly focused and directed to the sample. The fluorescence emission originating from two-photon excitation is collected with a spherical mirror, and focused on the entrance slit of an imaging grating spectrometer (Jobin Yvon Triax 550). A small part of the beam intensity is reflected with a glass, placed before the sample, to the reference detector (Molectron).

Nonlinear 2PA spectrum is obtained by tuning the wavelength of frequency-doubled OPA output and measuring the intensity of the resulting two-photon excited fluorescence. The tuning of OPA and data collection is computercontrolled with a LabView routine, which automatically normalized the fluorescence signal intensity to the square of the excitation intensity, taken from reference channel.

Absolute TPA cross section is measured at λ_ΘX = 930 nm by using the relative fluorescence method described in J. Phys. Chem. B 109, 7223-7236, (2005). One of the conjugated porphyrin dimers (yPyyPy), studied therein is used as a reference sample.

The TPA spectrum is then plotted as the σ₂ value versus excitation frequency. For this representation, the power density of excitation is recalculated to photon density per second per square centimeter.

One- and two-photon absorption spectroscopy of non-symmetrical phthalo-naphthalocyanine

Pc₃Nc (4):

Figure 1 shows the long-wavelength part of 1PA spectrum of (4) in dichloromethane solution. The solid line represents the best fit of the lowest-frequency (Q1) band to the Voigt function. The corresponding Gaussian and Lorentzian widths, as well as the maximum 1 PA cross section value are presented in Table 1.

Vertical arrows in Fig. 1 show the limits of laser frequency range, where the 2PA spectrum is measured in solution. The high-frequency boundary (right arrow) corresponds to the point, where the power dependence of fluorescence signal starts to decline from quadratic as a result of non-negligible 1 PA contribution. Dashed arrow indicates a frequency of Ti-Saphhire amplifier (790 nm) used for two-photon excitation of (4) in polyethylene film at 77K. Due to much narrower Q₁ band, less contribution of one-photon hot-band absorption, and higher excitation power, the power law is quadratic and the 2PA cross section may be detected in these very strong resonance enhancement conditions. Figure 2 demonstrates the 2PA spectrum of (4) in dichloromethane solution at room temperature (open circles). An open square represents the datum obtained in polyethylene film at 77K. The Voigt fitting of the whole profile is done approximately due to deficiency of data near the maximum.

The solid curve, shown in Fig. 2, is a best fit obtained for the spectral shape of 2PA in liquid solution, with the assumption that the maximum of the band coincides with the experimentally determined center of one-photon Q 1 -transition. The corresponding best fit values of Gaussian and Lorentzian widths are presented in Table 1. The maximum 2PA cross section, found as an extrapolation of the Voigt fit to the central frequency is extremely large (- 7.2 x 10⁴ GM).

The results show that (4) provides an extremely high intrinsic femtosecond 2PA cross section (10^~47- 10^~46) in the excitation region of 800 - 950 nm.

Table 1. One- and two-photon absorption properties (in dichloromethane) and photo- tautomerization quantum efficiency (in PVB film)) of two tautomeric forms of Pc3Nc

σi,2° - one- and two-photon absorption maximum cross sections,

λmax - 1 PA peak wavelength,

δi,₂ - Gaussian widths of 1PA and 2PA profiles,

Ti - Lorentzian widths of 1 PA and 2PA profiles,

TR - radiative lifetime,

φT - quantum efficiency of tautomerziation.

^•Calculated from the oscillator strength value; "measured in PVB film at 1OK (from J. Phys. Chem. A 101, 6202-6213 (1997)).

Application example 2

Experimental method generally is as described in example 1 ; absolute 2 photon absorption (2PA) cross section is measured at λ_ΘX=897 nm using relative fluorescence [see M. Drobizhev, Y, Stepanenko, Y. Dzenis, A. Karotki, A. Rebane, P.N. Taylor, H. L. Anderson, "Extremely strong near-IR two-photon absorption in conjugated porphyrin dimers: Quantitative description with three-essential-states model", J. Phys. Chem. B 109, 7223- 7236 (2005), or patent applications mentioned above].

Measured cross-section values, concentrations, linear extinction coefficients, quantum yields, stable switching temperature and FOM (for maximum measured cross-sections) are summarized in Table 2; compound numbers are those of compounds listed in the above preparation examples.

Summarizing the data, it is concluded that the compounds (7) and (13) are the most promising from the point of view of 2PA cross-section. The highest temperature stability is found for compounds (11) and (5), (12). Compound (11) is also found preferable in regard of quantum yields.

Claims

Claims:

1. A method of optical data storage including recording and reading of information comprising the steps

(a) preparation of the metastable tautomer (T∑form) of a suitable phthalocyanine as the recording dye by illuminating the recording medium containing the phthalocyanine resonantly with Qi-band of Ti tautomer;

(b) writing the bits of information into the bulk of the disk, e.g. containing a multitude of data layers, by using near-resonance two-photon excitation of T∑form (T∑→ Ti transformation of the recording dye); and

(c) reading out the bits with near resonant excitation and confocal scheme of collection of fluorescence of form Ti.

2. Method of claim 1 , further comprising the step of data erasing by (d) illuminating the recording medium in resonance with Ti tautomer absorption, or by increasing the temperature and repeating step (a), thus realizing a rewritable, high density 3 dimensional optical data medium.

3. Method of claim 1, where in steps (a), (b) and (c), the temperature is preferably kept in the range from 50 to 300K.

4. Method of any of claims 1-3, wherein the phthalocyanine in the recording medium conforms to formula A

or a tautomeric or mesomeric form and or metal complex thereof, wherein Gi, G₂, G₃, G₄, Y and Y' independently are H, OH, halogen, nitro, COOG₉, Ci-C₂₂alkyl, C_r C₂₂alkoxy, C_rC₂₂alkylthio, C₄-Ci₂cycloalkyl, C₄-Ci₂cycloalkoxy, C₄-Ci₂cycloalkylthio, aryl, aryloxy, arylthio, wherein each alkyl or alkoxy or alkylthio or aryl or aryloxy or arylthio moiety may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each aryl or aryloxy or arylthio moiety may further be substituted by alkyl or alkoxy; and wherein each alkyl or alkoxy or alkylthio moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, S, CO, COO, CONH, OCOO, OCONH, NHCONH; G₅ and G₆ indepently are H, OH, halogen, Ci-Ci₂alkyl, Ci-Ci₂alkoxy;

G₉ is H, C_rC₂₂alkyl, C₄-Ci₂cycloalkyl, wherein each alkyl may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; and wherein 2 vicinal substituents on a phenyl ring, preferably G₃, G₄, and more preferably Y, Y', optionally may be linked to form a 4-membered bridge (CH)_xNy, where x is 2 or 3 or 4, y is O or 1 or 2 and x+y =4, to form an annellated aromatic ring.

5. Non-resonant multi-photon absorption material containing a compound of the formula I, I' and/or I"

or a tautomeric or mesomeric form thereof, wherein

Gi, G₂, G₃, G₄, Gii, Gi2, Gi₃, Gi₄, G₂i, G₂₂, G₂₃ and G₂₄, independently, are H, OH, halogen, COOG₉, C_rC₂₂alkyl, C_rC₂₂alkoxy, C_rC₂₂alkylthio, C₄-Ci₂cycloalkyl, C₄-Ci₂cycloalkoxy, wherein each alkyl or alkoxy or alkylthio moiety may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy or alkylthio moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; or a vicinal pair of residues G₃ and G₄, Gi₃ and Gi₄ and/or G₂₃ and G₂₄ together form the annellating group -Xi=C(G₇)-C(G₈)=X₂- while further residues d and G₂, Gn and Gi₂, G₂i and G₂₂ attached to the same phenyl ring are as defined for G₅ and G₆ below; G₅ and G₆ indepently are H, OH, halogen, C_rCi₂alkyl, C_rCi₂alkoxy; G₇ and G₈ indepently are H, OH, halogen, COOG₉, Ci-C₂₂alkyl, Ci-C₂₂alkoxy, Ci-C₂₂alkylthio, C₄-Ci₂cycloalkyl, C₄-Ci₂cycloalkoxy, wherein each alkyl or alkoxy or alkylthio moiety may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy or alkylthio moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; or G₇ and G₈ together with the carbon atoms they are bonding to may be bridged together to form an annellated carbocyclic 6-membered aromatic ring, which is unsubstituted or substituted by OH, halogen, COOG₉, C_rC₂₂alkyl, C_rC₂₂alkoxy, C_rC₂₂alkylthio, C₄- Ci₂cycloalkyl, C₄-Ci₂cycloalkoxy, wherein each alkyl or alkoxy or alkylthio moiety may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy or alkylthio moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; G₉ is H, C_rC₂₂alkyl, C₄-Ci₂cycloalkyl, wherein each alkyl may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; Xi and X₂ indepently are CH or N;

D stands for deuterium or an alkali atom such as Li or Na, and one of the residues D may still be unmodified hydrogen; and M is a divalent metal atom, for example selected from Mg, Zn, Pd.

6. Material of claim 5 which is an optical data storage medium comprising a substrate and at least one recording layer, the recording layer containing the compound of the formula I, I' and/or I".

7. Material of claim 5 comprising the compound of the formula I, I' and/or I" as sensitizing dye or light emission element, and at least one further component suitable for initiation of a chemical reaction, polymerization reaction, colouration, refractive index modulation.

8. Method for the 3 dimensional optical addressing in a bulk material by 2 photon absorption of a suitable phthalocyanine as the sensitizing dye, especially a phthalocyanine deviating from C₄-symmetry.

9. Method of claim 8 for optical information storage, photodynamic therapy such as cancer therapy, initiation of a chemical reaction, polymerization, colouration, refractive index modulation, light emission, photoshaping, rational drug delivery.

10. Method of claim 8 for optical data storage, wherein data writing is achieved by 2 photon absorption of a suitable phthalocyanine as the recording dye, especially a phthalocyanine deviating from C₄-symmetry.

11. Method of claim 9, wherein the recording dye is a compound of formula AJJ' and/or I" as described in claims 4 or 5.

12. Method of claim 8, wherein the recording dye is a compound of formula A, I, I' and/or I" as described in claims 4 or 5.

13. Use of a phthalocyanine compound, especially deviating from C₄-symmetry, for optical data storage in a bulk material or a multitude of recording layers by 2 photon absorption.

14. Use of a compound of formula I, I' and/or I" as described in claim 5 as a non-resonant sensitizing dye or light emission element, especially for optical information storage, photodynamic therapy, cancer therapy, refractive index modulation, light emission, photoshaping, rational drug delivery, or for the initiation of a chemical reaction such as polymerization, colouration.

15. Use of a compound of formula I, I' and/or I" according to claim 14 as a recording dye for optical data storage.

16. A compound of formula I or I' or I" according to claim 5, or a tautomeric or mesomeric form thereof, deviating from C₄, especially from C₄ and C₂-symmetry relative to the axis perpendicular to the ring plane, wherein Gi₃ and Gi₄, independently, are H, OH, halogen, COOG₉, CrC₂₂alkyl, CrC₂₂alkoxy, Ci-C₂₂alkylthio, C₄-Ci₂cycloalkyl, C₄-Ci₂cycloalkoxy, where each alkyl or alkoxy or alkylthio moiety may be substituted by OH, halogen, amino, nitro, phenyl, phenoxy, carboxy; and wherein each alkyl or alkoxy or alkylthio moiety containing 2 or more carbon atoms may be interrupted in the carbon chain by O, NH, CO, COO, CONH, OCOO, OCONH, NHCONH; or wherein each of the vicinal substituents G₃ and G₄, Gi₃ and Gi₄, G₂₃ and G₂₄, in each case together form an annellating group -Xi=C(G₇)-C(G₈)=X₂-; with the exception of compounds of the formula I wherein

(a) one of each pair d or G₂, Gn or Gi₂, and G₂i or G₂₂ is Ci-d₂alkoxy while the other is hydrogen,

(b) each of G₃, G₄, G₅, G₆, Gi₃, Gi₄, G₂₃, G₂₄ is hydrogen, and

(c) any of G₇ and G₈ are Ci-d₂alkoxy or C_rC₂₂alkylthio or both of G₇ and G₈ are hydrogen or the bridging group -CH=CH-CH=CH-.