Synthesis, Structure, and UV–Vis Characterization of Antimony(III) Phthalocyanine: [(SbPc)2(Sb2I8)(SbBr3)]2

Abstract

A new antimony(III)–phthalocyanine complex with the formula of [(SbPc)2(Sb2I8)(SbBr3)]2 has been obtained in the reaction of pure antimony powder with phthalonitrile under the oxidation conditions by iodine monobromide vapors. The complex crystallizes in the centrosymmetric space group of the triclinic system. Both independent (SbPc)+ units exhibit non-planar conformation, since the Sb(III) is larger than the equilibrium cavity size of the ring and cannot be accommodated without its expansion; thus, the metal protrudes out of the cavity, forming a saucer shape. The centrosymmetric anionic unit of the crystal consists of two (Sb2I8)2− interacted anionic units forming (Sb4I16)4− anionic complex that interacts with two SbBr3 molecules to form [Sb6I16Br6]4− anionic aggregate. Each [Sb6I16Br6]4− anionic aggregate is surrounded by four (SbPc)+ cations forming a supramolecular centrosymmetric (SbPc)4[Sb6I16Br6] complex. Translationally related (SbPc)4[Sb6I16Br6] molecules form a stacking structure along the [100] and [011] directions with N4–N4 distances of 3.55 and 3.53 Å, respectively, between the back-to-back-oriented saucer-shaped (SbPc)+ units. The interaction between the building units of the crystal was analyzed using the Hirshfeld surface and the analysis of the 2D fingerprint plots. The UV–Vis absorption spectra of crystal 1 were taken in CH2Cl2 and toluene solutions in the concentration range from 10−5 to 10−6 mol/L. No significant changes related to aggregation in solutions were observed. The Q-band in toluene solution is red shifted by ~15 nm in comparison to that in CH2Cl2 solution. Oxidation of (SbPc)4[Sb6I16Br6] yields SbVPc derivative. Both SbIII and SbV phthalocyanine derivatives absorb near infrared light (600–900 nm), which should be intriguing from the point of view of potential use as photosensitizers for PDT and as an infrared cut filter for plasma display and silicon photodiodes.