Optical recording medium using formazan metal complex dye and photo-stabilizing method

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an optical recording medium using a formazan metal complex dye in a recording layer and a method for photo-stabilizing a dye.

2. Prior Art

In recent years, optical recording discs of the write-once, rewritable or erasable and other types have been of great interest as high capacity information carrying media. Some optical recording discs use a dye film composed mainly of a dye as their recording layer. From a structural aspect, commonly used optical recording discs are classified into an air-sandwich structure type having an air space on a dye base recording layer and a close contact type having a reflective layer in close contact with a dye base recording layer. The latter has the advantage of enabling readout in accordance with the compact disc (CD) standard. For instance reference is made to Nikkei Electronics, Jan. 23, 1989, No. 465, page 107; the Functional Dye Department of the Kinki Chemical Society, Mar. 3, 1989, Osaka Science & Technology Center; and Proceedings SPIE--The International Society for Optical Engineering, Vol. 1078, pp. 80-87, "Optical Data Storage Topical Meeting", 17-19, January 1989, Los Angels.

The dyes used in such recording layers must be chemically stable and resistant to light. Since the recording layer is generally formed by spin coating from the manufacturing and cost points of view, the dyes must also have a sufficient solubility in certain solvents to form a coating solution. With respect to these requirements, phthalocyanine dyes are believed preferable for chemical stability and light resistance. However, the phthalocyanine dyes are substantially insoluble in most organic solvents and thus impractical unless they are subject to a solubilizing treatment as by introducing a substituent to convert into a soluble structure. They also have the disadvantages of a less variable wavelength range and an increased cost of manufacture.

Several metal complex dyes are known to meet the requirements of chemical stability and light resistance. For example, azo metal complex dyes-are disclosed in Japanese Patent Application Kokai (JP-A) No. 268994/1991 and bidentate formazan nickel complex dyes are disclosed in JP-A 254038/1985 and 144997/1987. The metal complex dyes are fully resistant to light, but generally have low recording sensitivity and relatively low solubility. They are soluble only in selected solvents. Another problem is crystallization occurring in a spin coated film. The bidentate formazan nickel complex dyes have a somewhat longer absorption wavelength and are deemed rather impractical when the wavelength (780 nm) of a semiconductor laser currently utilized for recording and readout of optical discs is taken into account. Since it is essential to shorten the wavelength of laser light for the advanced higher density recording technology under development, there is a strong demand to have a dye skeleton capable of meeting such a requirement too.

As is well known in the art, cyanine dyes are widely used in recording layers. The cyanine dyes are advantageous with respect to optical properties, solubility and manufacture cost, but extremely less resistant to light because of the sensitization action of singlet oxygen. As a general rule, photo-stabilizers are combined therewith. Typical photo-stabilizers are metal complexes such as nickel complexes of bis(phenylenedithiol). These metal complexes function as singlet oxygen quenchers while degradation of the complexes themselves and low solubility due to their plane configuration are problems. Also undesirably, their preparation is accompanied by disgusting smell and an increased cost.

SUMMARY OF THE INVENTION

Therefore, a primary object of the present invention is to provide an optical recording medium which uses a formazan metal complex dye having good solubility and an appropriate thermal decomposition temperature and which features high sensitivity, especially high recording sensitivity, light resistance, high reflectance over a wide wavelength range, can accommodate laser light of the current wavelength and the future shorter wavelength, and is stable against variations and drifts of the oscillation wavelength of a laser.

Another object of the present invention is to provide an optical recording medium which uses a light-absorbing dye and a formazan metal complex dye as a photo-stabilizer therefor and which is resistant to light, easy to manufacture, typically easy to coat a recording layer, and excellent in performance.

A further object of the present invention is to provide a method for stabilizing dyes, typically light-absorbing dyes against light to effectively prevent their photo-degradation.

According to a first aspect of the present invention, there is provided an optical recording medium having a recording layer comprising at least one dye selected from formazan metal complex dyes of the following general formulae (I) and (II). ##STR1## The symbols in formulae (I) and (II) have the following meaning.

M is a divalent metal atom.

A.sub.1 is a group represented by ##STR2## wherein Q.sub.1 is a group of atoms necessary to form with C and N a five or six-membered heteroaromatic ring which may have fused ring.

A.sub.2 is a group represented by A.sub.21 or A.sub.22 : ##STR3## wherein Q.sub.2 is a group of atoms necessary to form with C and N a nine of ten-membered heteroaromatic ring which may have a fused ring, Q.sub.3 is a group of atoms necessary to form with C a five or six-membered heteroaromatic ring or benzene ring which may have a fused ring, Z is selected from the group consisting of an oxy (--O--), thio (--S--), imino (--NH--), oxycarbonyl (--O--CO--), iminocarbonyl (--NH--CO--), and iminosulfonyl (--NH--SO.sub.2 --) group, each of A.sub.1, A.sub.21 and A.sub.22 at its C is attached to N in the formazan skeleton, each of A.sub.1 and A.sub.21 at its N coordinates to M, and A.sub.22 at its Z coordinates to M.

Y is selected from the group consisting of an aromatic, alkyl, acyl, alkoxycarbonyl, cyano, nitro, alkoxy and alkylthio group.

R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 are independently selected from the group consisting of a hydrogen atom, alkyl group, alkoxy group, nitro group, cyano group, halogen atom, aryl group, aryloxy group, acyl group, alkoxycarbonyl group, carbamoyl group, and amino group, at least one of R.sub.4 and R.sub.5 is a hydrogen atom.

Letter n representing the number of formazan ligands coordinating to M is equal to 1 or 2. X is a counter ion to the formazan metal complex. Letter k is a number necessary to provide a balance of electric charge. The broken lines in formulae (I) and (II) represent coordinate bonds to M.

Several preferred embodiments are described below. M is Fe, Co, Ni, Cu, Zn, or Pd. The five or six-membered heteroaromatic ring which is formed by Q.sub.1 in A.sub.1 is a pyridine, thiazole, benzothiazole, oxazole, benzoxazole, or isoquinoline ring. The nine or ten-membered heteroaromatic ring which is formed by Q.sub.2 in A.sub.21 is a quinoline ring. The ring formed by Q.sub.3 in A.sub.22 is a benzene ring. A.sub.1 or A.sub.21 is preferred in a dye of formula (I) or a dye of formula (II).

The formazan metal complex dye is preferably of the following general formula (III). ##STR4##

Y and R.sub.1 to R.sub.5 are as defined above; R.sub.6, R.sub.7, and R.sub.8 are independently selected from the group consisting of a hydrogen atom, halogen atom, nitro group, alkyl group, and cyano group; and the broken lines in formula (III) represent coordinate bonds to Ni.

In another preferred embodiment, the recording layer further contains a light absorbing dye which is typically a cyanine dye. In a second aspect, the invention provides a method for photo-stabilizing a dye with a formazan metal complex dye of formula (I) or (II).

FUNCTION AND ADVANTAGES

The formazan metal complex dye used herein has a formazan ligand of one molecule coordinated to the center metal atom M at three points as shown by formulae (I) and (II). The tridentate ligand affords relatively great steric hindrance as compared with the metal complexes of JP-A 254038/1985 and 144997/1987 in which two formazan ligands coordinate to nickel each at two points to form a fully symmetrical, four-coordinate, substantially plane tetragonal structure. More particularly, where two formazan ligands coordinate to the center metal atom each at three points to form a six-coordinate octahedral structure, this structure has the formazan ligands crossed with each other, resulting in enhanced steric hindrance. Where a single formazan ligand coordinates to the center metal atom at three points to form a four-coordinate metal complex with another ligand, there results a tetrahedral structure or a plane tetragonal structure. Based on the structure of the formazan ligand, the formazan metal complex dye used in the present invention is expected to assume a structure approximate to a plane tetragonal structure. The formazan metal complex dye assuming such a structure loses symmetry and is rich in steric hindrance as compared with the complex wherein bidentate ligands form a plane tetragonal structure.

As a consequence, the formazan metal complex dye of the invention is improved in solubility to enable easy formation of a coating film and has an appropriate heat decomposition temperature and high sensitivity when used as a light-absorbing dye in a recording layer of an optical recording medium. Since the inventive dye has a high coefficient of light absorption, its thin film has a high refractive index satisfying the properties required from the recording principle. Since the inventive dye has high reflectance over a wide wavelength range, it can accommodate to not only the currently available optical recording media, but also future optical recording media adapted for higher density and shorter wavelength recording. The inventive dye experiences minimal change of its properties by variations and drifts of the oscillation wavelength of a laser. When a dye film serving as a recording layer is formed from the inventive dye, its properties depend only a little on film thickness and other factors, allowing a film to be formed without undue care. Light resistance is high. Synthesis of the inventive dye is relatively easy.

The formazan metal complex dye of the invention has the function of a photo-stabilizer as well as the function of a light-absorbing dye. More particularly, since the inventive dye effectively traps the light energy the co-existing light-absorbing dye has absorbed through energy transfer and thermally deactivates or quenches this energy without giving it to oxygen molecules or the like, the inventive dye substantially restrains the sensitization action of singlet oxygen on the co-existing light-absorbing dye, thereby stabilizing the light-absorbing dye. Then by using the formazan metal complex dye as a photo-stabilizer in a recording layer along with a light-absorbing agent, there is obtained an optical recording medium having improved light resistance and satisfactory performance.

The action of the formazan metal complex dye as a photo-stabilizer is effective to not only light-absorbing dyes as used in the recording layer of optical recording media, but also ordinary dyes for preventing photo-degradation thereof.

Also the formazan metal complex dye of the invention is effective in small amounts since its function as a photo-stabilizer is extremely strong.

It is to be noted that cyanine dyes are conventionally used in the recording layer of optical recording media and metal complexes of bis(phenylenedithiol) serving as single oxygen quenchers are used as photo-stabilizers to compensate for the low light resistance of cyanine dyes. These metal complexes, however, are less soluble and tend to lower their function as a singlet oxygen quencher, losing the function of a photo-stabilizer. In contrast, the formazan metal complex dye of the invention eliminates these problems. An optical recording medium using the formazan metal complex dye of the invention affords superior electrical properties to media using conventional metal complexes of bis(phenylenedithiol).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a portion of an optical recording disc according to one embodiment of the invention.

FIG. 2 is a graph showing transmission and reflection spectra of a formazan metal complex dye (No. 1-44) according to the invention.

FIG. 3 is a graph showing transmission and reflection spectra of a formazan metal complex dye (No. 1-45) according to the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The formazan metal complex dyes used in the present invention are represented by formulae (I) and (II). ##STR5##

M is a divalent metal atom, for example, Fe, Co, Ni, Cu, Zn, and Pd, preferably Ni, Cu, and Zn, with Ni being most preferred.

In formula (I), A.sub.1 is a group represented by ##STR6## wherein Q.sub.1 is a group of atoms necessary to form a five or six-membered heteroaromatic ring with the carbon and nitrogen atoms. The heteroaromatic ring may further have a fused ring. Examples of the heteroaromatic ring which may have a fused ring include nitrogenous heteroaromatic rings such as pyridine, thiazole, benzothiazole, oxazole, benzoxazole, and isoquinoline rings, with the pyridine and isoquinoline rings being preferred, especially the pyridine ring.

In formula (II), A.sub.2 is a group represented by A.sub.21 or A.sub.22 : ##STR7##

In A.sub.21, Q.sub.2 is a group of atoms necessary to form a nine or ten-membered heteroaromatic ring with the carbon and nitrogen atoms. The heteroaromatic ring may further have a fused ring. The heteroaromatic ring which may have a fused ring is a quinoline ring, for example.

In A.sub.22, Q.sub.3 is a group of atoms necessary to form a five or six-membered heteroaromatic ring or benzene ring with the carbon atoms. These rings may further have a fused ring. Among them, the heteroaromatic ring which may have a fused ring is as exemplified above in conjunction with A.sub.1 and A.sub.21. Examples of the benzene ring which may have a fused ring include benzene, naphthalene and anthracene rings, with the benzene ring being preferred.

Z represents a divalent group containing an atom coordinating to M and is an oxy (--O--), thio (--S--), imino (--NH--), oxycarbonyl (--O--CO--), iminocarbonyl (--NH--CO--), or iminosulfonyl (--NH--SO2--) group, with the oxy (--O--) and oxycarbonyl (--O--CO--) groups being preferred.

Each of A.sub.1, A.sub.21 and A.sub.22 at its carbon atom is attached to the adjacent nitrogen atom in the formazan skeleton. The coordination bond to M is formed by the nitrogen atom in the heteroaromatic ring for A.sub.1 and A.sub.21 and by Z for A.sub.22.

Illustrative examples of A.sub.1, A.sub.21 and A.sub.22 are shown below. Note that A-1, A-2, A-4 to A-7 are examples of A.sub.1, A-3 is an example of A.sub.21, and A-8 to A-13 are examples of A.sub.22. The asterisk (*) represents the position bonded to N in the formazan skeleton and double asterisks (**) represents the position of coordination bond to M. ##STR8##

In these examples, R.sub.6 to R.sub.19 are independently a hydrogen atom, halogen atom (e.g., fluorine atom), nitro group, cyano group, or alkyl group preferably having 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms (e.g., methyl).

Among A.sub.1, A.sub.21 and A.sub.22, preferred are A.sub.1 and A.sub.21. A.sub.1 is especially preferred.

In formulae (I) and (II), Y is an aromatic, alkyl, acyl, alkoxycarbonyl, cyano, nitro, alkoxy or alkylthio group. Examples of the aromatic group include phenyl, naphthyl, anthryl, and 1,3-dioxaindan-5-yl groups, with those groups having 5 to 14 carbon atoms being preferred, especially six-membered rings. The aromatic group may further have a substituent. Exemplary substituents include alkyl groups (e.g., methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl), alkoxy groups (e.g., methoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec -butoxy, tert-butoxy, and 2,3-pentafluoropropoxy), amino groups (e.g., diethylamino and dichlorodiethylamino), halogen atoms (e.g., chlorine and fluorine), aryl groups (e.g., phenyl), aryloxy groups (e.g., phenoxy), alkoxycarbonyl groups (e.g., methoxycarbonyl), acyl groups (e.g., propionyl, butyryl, isobutyryl, valeryl, and isovaleryl), carbamoyl, cyano, and nitro groups. The alkyl groups represented by Y are preferably those having 1 to 18 carbon atoms, especially 2 to 10 carbon atoms, which may be normal or branched. Exemplary are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 1-methylbutyl, n-hexyl, n-heptyl, and 1-ethylpentyl groups. Branched alkyl groups having 3 to 8 carbon atoms are preferred. The acyl group represented by Y includes a propionyl group. The alkoxycarbonyl group includes a propoxycarbonyl group. The alkoxy group includes ethoxy and butoxy groups. The alkylthio groups include methylthio and butylthio groups. The alkyl moiety of these alkyl-bearing groups should preferably have 1 to 8 carbon atoms, especially 1 to 6 carbon atoms.

In formulae (I) and (II), R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 are independently a hydrogen atom, alkyl group (e.g., methyl, 1-methylpropyl and trifluoromethyl), alkoxy group (e.g., ethoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, methoxy, octadecyloxy, and hexadecyloxy), nitro group, cyano group, halogen atom (e.g., fluorine and chlorine), aryl group (e.g., phenyl and p-diethylaminophenyl), aryloxy group (e.g., phenoxy), acyl group (e.g., propionyl), alkoxycarbonyl group (e.g., methoxycarbonyl), carbamoyl group, or amino group (e.g., diethylamino). At least one of R.sub.4 and R.sub.5 is a hydrogen atom. The alkyl group or alkyl moiety should preferably have 1 to 20 carbon atoms, especially 1 to 8 carbon atoms. The aryl group or aryl moiety should preferably have 5 to 10 carbon atoms, with a six-membered ring being especially preferred.

In one preferred embodiment, Y is an aromatic group such as phenyl, a branched alkyl group having 3 to 6 carbon atoms, or an alkoxy or acyl group having a branched alkyl group having 3 to 6 carbon atoms. Also preferably Y is a branched alkyl group having 3 to 8 carbon atoms. Each of R.sub.1 to R.sub.5 is preferably a branched alkyl group having 3 to 6 carbon atoms, an alkoxy group having a branched alkyl moiety, or an electron attracting group such as nitro and cyano groups. Most preferably R.sub.2 is a nitro, cyano or alkoxy group. Where R.sub.2 is not a nitro, cyano or alkoxy group, A.sub.1, A.sub.21 or A.sub.22 has preferably an electron attracting group such as nitro and cyano groups.

In formulae (I) and (II), n representing the number of formazan ligands coordinating to M is equal to 1 or 2. The number of ligands depends on the type of M, that is, n=1 for Ni, Cu, Co, Zn, and Fe, and n=2 for Ni, Co, Pd, Zn, and Fe. Where n=2, the formazan ligands coordinating to M are generally identical, but may be different in some cases. These metal complexes are deemed to assume a structure approximate to a plane tetragonal structure if they are four coordinate and an octahedral structure if they are six coordinate. Then, where n=1, there is formed a structure wherein another ligand coordinates at the remaining coordinate position. What can be the other ligand is a solvent used in the reaction to form the metal complex (e.g., methanol, ethanol, dioxane, pyridine, acetic acid, water, and hydroxide ion), an anion of a metal salt used in introducing a metal (e.g., chloride ion, bromide ion, iodide ion and cyanide ion), or a thiocyanate ion, isothiocyanate ion, ammonia or carbon monoxide to be introduced by ligand exchange reaction after complex formation.

In formulae (I) and (II), X is a counter ion to the formazan metal complex, and k is a number necessary to provide a balance of electric charge. Most formazan metal complex dyes have an electric charge of -2, 0 and 1 valence. In the case of 0 valence, k=0, that is, no counter ion is present. Examples of X include anions such as halide ion, perchlorate ion, tungstate ion, tetrafluoroborate ion, hexafluorophosphate ion, and toluenesulfonate ion, and cations such as ammonium ion, tetraalkylammonium ion, e.g., (C.sub.4 H.sub.9).sub.4 N.sup.+ and (C.sub.2 H.sub.5).sub.4 N.sup.+.

The broken lines in formulae (I) and (II) represent coordinate bonds to M.

Among the formazan metal complex dyes of formulae (I) and (II), those dyes of formula (III) are preferred. ##STR9##

In formula (III), Y and R.sub.1 to R.sub.5 are as defined for formulae (I) and (II), with their preferred examples being the same. R.sub.6 to R.sub.8 are as previously defined in A-1 example of A.sub.1, with hydrogen and nitro being preferred.

Illustrative, non-limiting examples of the formazan metal complex dye are given below. These examples are expressed in accordance with formulae (I) and (II) by classifying in terms of A.sub.1, A.sub.21 and A.sub.22. Where a ligand other than the formazan ligand coordinates, the number of counter ions is shown provided that it is an electrically neutral one. Alkyl and similar groups may be either normal or branched unless otherwise stated.

__________________________________________________________________________ ##STR10## (A-1) Com- pound No. R.sub.1 R.sub.2 R.sub.3 R.sub.4 R.sub.5 Y R.sub.6 R.sub.7 R.sub.8 M n k X __________________________________________________________________________ 1-1 H H H H H ##STR11## NO.sub.2 H H Ni 1 1 ClO.sub.4.sup.- 3 1-2 H CH.sub.3 H CH.sub.3 H ##STR12## NO.sub.2 H H Ni 1 1 BF.sub.4.sup.- 1-3 H ##STR13## H H H ##STR14## NO.sub.2 H H Ni 1 1 BF.sub.4.sup.- 1-4 H C.sub.2 H.sub.5 O H H H ##STR15## H H F Ni 1 1 BF.sub.4.sup.- 1-5 H H H H H ##STR16## NO.sub.2 H H Ni 1 1 ClO.sub.4.sup.- 9 1-6 H NO.sub.2 H H H ##STR17## H H H Ni 1 1 ClO.sub.4.sup.- . 1-7 H CN H H H ##STR18## H CH.sub.3 H Ni 1 1 ClO.sub.4.sup.- 1-8 H NO.sub.2 H H H ##STR19## H H H Ni 1 1 ClO.sub.4.sup.- 1-9 H NO.sub.2 H H H ##STR20## H H H Ni 2 0 -- 1-10 H NO.sub.2 H H H ##STR21## H H H Ni 2 0 -- 1-11 H NO.sub.2 H H H ##STR22## H H H Ni 2 0 -- 1-12 H C.sub.4 H.sub.9 O H H H CN H H H Ni 2 0 -- 1-13 H C.sub.4 H.sub.9 O H H H NO.sub.2 H H H Ni 2 0 -- 1-14 H C.sub.4 H.sub.9 O H H H C.sub.2 H.sub.5 O H H H Ni 2 0 -- 1-15 H C.sub.4 H.sub.9 O H H H CH.sub.3 S H H H Ni 2 0 -- 1-16 H C.sub.4 H.sub.9 O H H H n-C.sub.4 H.sub.9 H H H Ni 2 0 -- 1-17 H C.sub.4 H.sub.9 O H H H t-C.sub.4 H.sub.9 H H H Ni 2 0 -- 1-18 H H H H H ##STR23## NO.sub.2 H H Cu 1 1 ClO.sub.4.sup.- 1-19 H ##STR24## H H H ##STR25## NO.sub.2 H H Cu 1 1 ClO.sub.4.sup.- 1-20 H C.sub.2 H.sub.5 O H H H ##STR26## H H F Cu 1 1 ClO.sub.4.sup.- 1-21 H H H H H ##STR27## NO.sub.2 H H Cu 1 1 BF.sub.4.sup.- 1-22 H NO.sub.2 H H H ##STR28## H H H Cu 1 1 ClO.sub.4.sup.- 1-23 H CN H H H ##STR29## H CH.sub.3 H Cu 1 1 ClO.sub.4.sup.- 1-24 H NO.sub.2 H H H ##STR30## H H H Cu 1 1 ClO.sub.4.sup.- 1-25 H NO.sub.2 H H H ##STR31## H H H Cu 1 1 ClO.sub.4.sup.- 1-26 H NO.sub.2 H H H ##STR32## H H H Cu 1 1 ClO.sub.4.sup.- 1-27 H NO.sub.2 H H H ##STR33## H H H Cu 1 1 ClO.sub.4.sup.- 1-28 H C.sub.4 H.sub.9 O H H H CN H H H Ni 2 0 -- 1-29 H C.sub.4 H.sub.9 O H H H NO.sub.2 H H H Ni 2 0 -- 1-30 H C.sub.4 H.sub.9 O H H H C.sub.2 H.sub.5 O H H H Ni 2 0 -- 1-31 H C.sub.4 H.sub.9 O H H H n-C.sub.4 H.sub.9 H H H Cu 1 1 BF.sub.4.sup.- 1-32 H C.sub.4 H.sub.9 O H H H t-C.sub.4 H.sub.9 H H H Cu 1 1 BF.sub.4.sup.- 1-33 H Cl H Cl H ##STR34## NO.sub.2 H H Co 2 0 -- 1-34 H C.sub.2 H.sub.5 O H H H ##STR35## H H H Co 2 0 -- 1-35 H NO.sub.2 H H H ##STR36## H H H Co 2 0 -- 1-36 H Cl H Cl H ##STR37## NO.sub.2 H H Pd 2 0 -- 1-37 H C.sub.2 H.sub.5 O H H H ##STR38## H H H Pd 2 0 -- 1-38 H NO.sub.2 H H H ##STR39## H H H Pd 2 0 -- 1-39 H C.sub.2 H.sub.5 O H H H ##STR40## H H H Zn 2 0 -- 1-40 H NO.sub.2 H H H ##STR41## H H H Zn 2 0 -- 1-41 H C.sub.2 H.sub.5 O H H H ##STR42## H H H Fe 2 0 -- 1-42 H NO.sub.2 H H H ##STR43## H H H Fe 2 0 -- 1-43 H H H H H ##STR44## H H H Ni 2 0 -- 1-44 H H H H H ##STR45## NO.sub.2 H H Ni 2 0 -- 1-45 H H H H H ##STR46## NO.sub.2 H H Ni 2 0 -- 1-46 H H H H H ##STR47## NO.sub.2 H H Ni 2 0 -- 1-47 H H H H H ##STR48## H H H Ni 2 0 -- 1-48 H H H H H ##STR49## NO.sub.2 H H Ni 2 0 -- 1-49 H H H H H ##STR50## H H H Ni 2 0 -- 1-50 H H H H H ##STR51## NO.sub.2 H H Ni 2 0 -- 1-51 H H H H H ##STR52## H NO.sub.2 H Ni 2 0 -- 1-52 H H H H H ##STR53## H H H Ni 2 0 -- 1-53 H H H H H ##STR54## H NO.sub.2 H Ni 2 0 -- 1-54 H H H H H ##STR55## NO.sub.2 H H Ni 2 0 --

1-55 H H H H H ##STR56## NO.sub.2 H H Ni 2 0 -- 1-56 H H H H H ##STR57## H NO.sub.2 H Ni 2 0 -- 1-57 H H H H H ##STR58## H H H Ni 2 0 -- 1-58 H H H H H ##STR59## NO.sub.2 H H Ni 2 0 -- 1-59 H H H H H ##STR60## NO.sub.2 H H Ni 2 0 -- 1-60 H H H H H ##STR61## CN H H Ni 2 0 -- 1-61 H H H H H ##STR62## CN H H Ni 2 0 -- 1-62 H H H H H ##STR63## NO.sub.2 H H Ni 2 0 -- 1-63 H H H H H ##STR64## CN H H Ni 2 0 -- 1-64 H ##STR65## H H H ##STR66## NO.sub.2 H H Ni 2 0 -- 1-65 H CH.sub.3 H CH.sub.3 H ##STR67## H NO.sub.2 H Ni 2 0 -- 1-66 CF.sub.3 H H H H ##STR68## NO.sub.2 H H Ni 2 0 -- 1-67 H CH.sub.3 O H H H ##STR69## H H H Ni 2 0 -- 1-68 CH.sub.3 O CH.sub.3 O H H H ##STR70## H H H Ni 2 0 -- 1-69 H C.sub.18 H.sub.37 O H H H ##STR71## NO.sub.2 H H Ni 2 0 -- 1-70 H ##STR72## H H H ##STR73## H H H Ni 2 0 -- 1-71 H F H F H ##STR74## CN H H Ni 2 0 -- 1-72 Cl Cl H H H ##STR75## H NO.sub.2 H Ni 2 0 -- 1-73 H ##STR76## H H H ##STR77## H H H Ni 2 0 -- 1-74 H ##STR78## H H H ##STR79## NO.sub.2 H H Ni 2 0 -- 1-75 ##STR80## H H H H ##STR81## NO.sub.2 H H Ni 2 0 -- 1-76 H ##STR82## H H H ##STR83## NO.sub.2 H H Ni 2 0 -- 1-77 H CN H H H ##STR84## H H H Ni 2 0 -- 1-78 H ##STR85## H H H ##STR86## NO.sub.2 H H Ni 2 0 -- 1-79 H ##STR87## H H H ##STR88## NO.sub.2 H H Ni 2 0 -- 1-80 CF.sub.3 H H