Synthesis and solvent effects on the spectroscopic properties of octatosylamido phthalocyanines

Octatosylamido-substituted metal-free, Ni(II) and Zn(II) phthalocyanines (pcs, 3a–c) have been synthesized from 4,5-dicyano-N,N’-ditosyl-o-phenylenediamine (2, tosyl: toluene-p-sulfonyl) in the presence of an anhydrous metal salt and a strong base. The new compounds have been characterized by elemental analysis, IR and UV-vis spectroscopy, different NMR techniques (1H, 13C, 1H–15N HSQC, 1H–13C HSQC and 1H–13C HMBC) and mass spectroscopy. The influence of the solvent on the 1H, 13C NMR and UV-vis spectra has been determined. In chloroform, 3a–c are able to form intramolecular hydrogen bonds between four NH and oxygen atoms from neighbouring tosyl units and two tosyl groups occur in one single molecule: while four tosyl units are in the pc plane, the other four are nearly vertical to it. They have different chemical environments because of the magnetic anisotropy of the pc ring. For this reason, in chloroform, each of the protons and carbon atoms gives two sets of signals in the 1H and 13C NMR spectra of pcs. In tetrahydrofuran, the intramolecular hydrogen bonding of pcs is disrupted and all tosyl units are located in the same environment. In the electronic spectra of 3a–c, all bands change with the solvent. This solvatochromism is caused by solvent basicity. Compounds 3a–c show rapid and reversible colour change upon addition of a base.