Naphthalocyanine dyes

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... 

Nalwa, H.S., Kobayashi, S., Kakuta, A. Third-order nonlinear optical properties of processable metallo-naphthalocyanine dyes. Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. B 6, 169-179 (1993)... 

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.

The phthalocyanines, naphthalocyanines, and certain of their metal derivatives (Figure 6.17) are infrared fluorophores. 61"64 As a class, they are exceptionally stable compounds, with copper (Cu) phthalocyanine (not a fluorophore) remaining intact above 300 °C in air. First used for textile dyeing in the last century and still widely used, there is a rich chemistry of phthalocyanines. Most derivatives can be made by prolonged heating of a phthalimide or phthalic acid derivative with a metal in powder or salt form at elevated temperature. Several derivatives absorb in the near-IR, and either fluoresce or phosphoresce. The electronic transitions of phthalocyanines are complex and have been extensively studied, at least in part because the symmetry of the molecule makes theoretical calculations of its spectroscopic behavior more tractable. Unsubstituted phthalocyanines and naphthalocyanines are, as a class, very insoluble in solvents other than, for instance, nitrobenzene. Sulfonated phthalocyanines are water soluble and exhibit spectra comparable to the parent derivative. Photolumines-cent phthalocyanines (Pcs) include SiPc, ZnPc, and PC itself. These compounds have been little used for practical infrared fluorometry to date however, Diatron Corpora-... 

Poly(2-hydroxyethyl methylmethacrylate) (PHEMA) has been used as a matrix for the detection of metal ions. 79 A near-IR dye (2,3-naphthalocyanine-tetrasulphonic acid) was immobilized in a polymer matrix which was attached to the reaction phase of two optical fibers. A mixture of the matrix and the dye was prepared by mixing PHEMA and dye in a 60/40 ratio. The optimum ratio of polymer and dye were not fully investigated. The dye/polymer mixture was applied to the tip of the probe in 10-to 15-/iL aliquots forming a thin coating on the probe after solvent evaporation as shown in Figure 7.9. 

Naphthalocyanine Derivatives. These dyes, which contain a naphthalocyanine skeleton as chromophore, show high absorption in the area around 830 nm, possess low melting points, and small heat conductivity. A disadvantage of the unsubstituated naphthalocyanine is its low solubility in organic solvents which do not attack the polymeric substrate material (generally polycarbonate) substituents improve solubility (see PHTHALOCYANINE compounds). 

Phthalocyanine and naphthalocyanine are guest dye dopants suitable for the near infrared (IR) region. PVK is used as usual, as the hole transport polymer, Alqs, or a sulforamide derivative (Al(qs)3) is used as the host dye. The absorbance spectra of the guest dyes are significantly different from the emission spectra of the host dyes. However, the high molar absorption of the host dye dopants result in such efficiencies of energy transfer that are comparable to quinacridone or rubrene dopants. 

Another class of long-wavelength dyes are the phthalo-cyanines and naphthalocyanines (Hgure3.19). At presenL foese dyes are less used in biochemistry owing to their lack of water solubility, their tendency to aggregate, and the lack of conjugatable forms. The spectral properties of the NIR dyes have been suimnarized in Refs. 4S, 54, and 55. 

Recently 2,3-naphthalocyanines (see also p. 708) have attracted much attention because of their potential use as semiconducting materials, in non-linear optics, as laser dyes and in photodynamic therapy [14]. Due to intermolecular interactions between the macrocycles, peripherally unsubstituted metal lophthalocyanines and also metallo-2,3-naphthalocyanines are practically insoluble in common organic solvents like chloroform or toluene. Solubility, however is necessary for many applications. Although it has been shown that soluble compounds are formed by inserting sidechains into the... 

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