Naphthalocyanines

The basic stmcture of a naphthalocyanine dye can be seen in Figure 6 (12). By varying the central atom Y, the organic (polymeric) group at the central atom, and the substituents and X, an adjustment to the desired property profile, especially improved solubihty, can be achieved. Naphthalocyanines with sihcon as central atom evoke special interest, eg, the biaxiahy substituted silicon—naphthalocyanine (13) wherein the central Si bears... 

Fig. 6. Dyes for WORM media phthalocyanine derivatives. The basic stmcture (12) of naphthalocyanine derivatives. Y = Si, Ge, Sn, Al, Ga, In, or a transition metal = ORj, OSiR R R, polymer. and represent substituents on the tings of the naphthalene system.

Given stringent requirements for effective sensitizers and the desire to use wavelengths further to the red for therapeutic appHcations, definition of newer sensitizers has been a principal area of research since about 1987. Expanded theoretical and experimental understanding of photophysics has been a key element in identifying new classes of potential sensitizers (93—98). Research has focused on cationic derivatives of Nile Blue (93), metaHo-phthalocyanines (94), naphthalocyanines (95), chlorin-type compounds (96), expanded ring porphyrinoids (97), as well as porphyrins other than hematoporphyrin and its derivatives (98). This work has also been reviewed (10,91). Instmmentation for photodynamic therapy has been reviewed (99). 

Naphthalocyanins, phthalocyanins, and porphyrins as sensitizers in photodynamic cancer therapy 98IZV836. 

Some additional derivatives containing extended 7t-systems in place of the benzene nucleus are naphthalene, anthracene (2,3-Ac) and phenanthrene (9,10-Phc). They also belong to the phthalocyanine family. For the naphthalene system two types of macrocyclcs, the 1,2-naph-thalocyanine (1,2-Nc) and the 2,3-naphthalocyanine (2,3-Nc), are known. 

Naphthalocyanines can be regarded as benzo-annulated phthalocyanines. The number of substituted naphthalocyaninc precursors leading to structural isomers is even higher than in the case of phthalocyanine formation. 1,2-Naphthalocyanine, e.g. 26,71 73 exists as at least four different isomers, even in the unsubstituted form (see p 736). 

Iron(ll) 2,11,20,29-Tetra(to7-buty I)-1,2-naphthalocyanine "typical Procedure 7 1... 

Naphthalene-2,3-dicarbonitrile itself or mono- or aisubstitutea derivatives can be used in the cyclization reaction to afford naphthalocyanines, e.g. formation of 27 from naphthalene-2,3-dicarbonitrile. 

Bis(ftTf-butyIisocyano)iron(II) 2,5,ll,14,20,23,29,32-Octaheptyl-2,3-naphthalocyanine (33) Typical Procedure 281... 

Analogously, the corresponding octa(phcnylsulfanyl)- (16 %), octa(phenylseianyl)- (51 %) and octa(phenyltellanyl)-substituted (35%) copper(II) 2,3-naphthalocyanines can be prepared. 

Treating naphthalene-2,3-dicarbonitrile with sodium 3-methylbut-l-oxide in 3-methylbutan-l-ol for five hours at reflux gives 2,3-naphthalocyanine 1, which, when stirred with methanol at room temperature, gives the metal-free 2,3-naphthalocyanine (2). 

Naphthalene-2,3-dicarbonitrile (0.89 g, 5 mmol) and (NH4)2Mo04 (0.002 g) were refluxed for 5 h in a solution of sodium 3-inethyIbut-l-oxide [made from Na (0.09 g) and anhyd 3-methylbutan-l-ol(IOOmL)J. Aftercoolingto80 C, the suspension was filtered and the precipitate was washed with MeOH. Forcomplete transformation of the disodium 2,3-naphthalocyanine (1) into the metal-free compound 2, the material was left for several h in MeOH at rt and then the precipitate was filtered and freed from impurities by extraction with MeOH and benzene yield 0.23 g (26%). 

An example of hydrogen/metal exchange has been reported for 1,6,10,15,19,24,28,33-octasub-stituted 2,3-naphthalocyanine 7. 

The exchange of lithium for lutetium(III) represents an example of metal/metal exchange in 2,3-naphthalocyanines. 

Lu(OAc)j (20 mg, 0.05 mol) was added to a solution of dilithium 2,3-naphthalocyanine (17 72 mg, 0.1 mmol) in quinoline (10 mL), previously deaerated with N2. The refluxing medium was stirred, under Nj, for 3 h. After cooling, the mixture was poured on top of an alumina column (20 g). The purple band, containing 2,3-Nc2Lu (18) associated with quinoline, was rapidly eluted with CH,C12. After complete removal of the solvents, the desired product was obtained as a dark solid yield 38 mg (47%). 

In a similar fashion, the triple-decker complex dilutetium(III) tris(l,2-naphthalocyanine) was prepared in 55% yield.205... 

Isocyanides may be coordinated to the central iron or ruthenium atom in the corresponding 2,3-naphthalocyanines, e.g. 7. 

Bis(l,4-diisocyanobenzene)iron(II) 2,3-Naphthalocyanine (7, R = 4-CNC6H4) Typical Procedure 452... 

By analogy to the reaction of simple phthalocyanines, oxidation and reduction of the central metal in 2,3-naphthalocyanines 3 has been carried out. 

Similarly, 2,3-naphthalocyanines can be formed by reduction of the central metal. 

Treatment of naphthalenc-2,3-dicarbonitriles with dichlorophenylboron gives only very low yields of phenylboron sub-2,3-naphthalocyanines.68... 

A 1,lO,l9,28-Tetraaza-2,3-naphthalocyanine 3 results from the cyclization of anhydride 2. 

Oxovanadium(IV) 6,I5,24,33-Tetraphenyl-l,10,19,28-tetraaza-2r3-naphthalocyanine (3) Single Procedure 4 ... 

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