Inorganic Chemistry, Vol.37, No.8, 1992-1999, 1998
Silicon and zinc coordination to peripheral catechol sites of (2,3,9,10,16,17,23,24-octahydroxyphthalocyaninato)nickel(II). Phthalocyanine coordination chemistry at the edge
(2.3.9.10.16,17,23,24-Octahydroxyphthalocyaninato)nickel (NiPc(OH)(8)) has been prepared by demethylation of (octamethoxyphthalocyaninato)nickel(II). Silylation of peripheral oxygen atoms using dimethyl-tert-butylsilyl chloride gave NiPc(OSi(t-Bu)Me-2)(8) as a convenient precursor to NiPc(OH)(8) with high solubility in hydrocarbon solvents. The coordination properties of peripheral catechol sites were investigated by treating NiPc(OH)s with Tp(Cum,Me)Zn(OH). A model study was first carried out by adding 5,6-dihydroxyphthalimide (H(2)PhtCat) to Tp(Cum,Me)Zn(OH). Partial deprotonation occurred to give Tp(Cum,Me)Zn(HPhtCat). Further deprotonation with NMe4(OH) gave (NMe4)[Tp(Cum,ME)Zn(PhtCat)] as the methanol solvate. H-1 NMR spectra recorded on Tp(Cum,Me)Zn(HPhtCat) show sharp resonances for equivalent arms of the Tp(Cum,Me) ligand, while Tp(Cum,Me) resonances for (NMe4)[Tp(Cum,Me)Zn(PhtCat)] appear broadened by slow site exchange about the strongly chelated catecholate ligand. Similarly, the reaction between NiPc(OH)(8) and Tp(Cum,Me)Zn(OH) occurred with partial deprotonation to give NiPc(OH)(4)(OZnTp(Cum,Me))(4) Structural characterization on crystals obtained from acetonitrile showed that Zn ions bond to single ring oxygen atoms at two sites and that they chelate to adjacent oxygen atoms at the other two ring sites. Cumenyl i-propyl substituents of the Tp(Cum,Me) ligands form hydrophobic pockets above and below the central metal of the phthalocyanine ring. These sites are occupied by acetonitrile solvent molecules positioned with hydrogen atoms directed toward the Ni atom in the crystal structure of the complex obtained by crystallization from a dichloromethane/acetonitrile solution. Addition of base to NiPc(OH)(4)(OZnTp(Cum,Me))(4) results in deprotonation of the remaining four OH groups and substantial red shifts for electronic transitions in the 400 and 600 nm regions of the phthalocyanine ring. Broadened H-1 NMR resonances for arms of the Tp(Cum,Me) ligands point to a chelated structure for the Zn atoms of (NMe4)(4)[NiPc(O(2)ZnTp(Cum,Me))(4)].