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

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 Sb^VPc derivative. Both Sb^III and Sb^V 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.