Molecular Structures of Chloro(phthalocyaninato)-aluminum(III) and -gallium(III) as Determined by Gas Electron Diffraction and Quantum Chemical Calculations: Quantum Chemical Calculations on Fluoro(phthalocyaninato)-aluminum(III) and -gallium(III), Chloro(tetrakis(1,2,5-thiadiazole)porphyrazinato)-aluminum(III) and -gallium(III) and Comparison with their X-ray Structures

Abstract

The molecular structures of chloro(phthalocyaninato)aluminum(III) (ClPcAl) and chloro(phthalocyaninato)gallium(III) (ClPcGa) have been determined by using the gas electron diffraction (GED) method and augmented by quantum chemical calculations. The molecular structures of fluoro(phthalocyaninato)aluminum(III) (FPcAl), fluoro(phthalocyaninato) gallium(III) (FPcGa), chloro(tetrakis(1,2,5-thiadiazole)porphyrazinato)aluminum(III) (ClTTDPzAl), and chloro(tetrakis(1,2,5-thiadiazole)porphyrazinato)gallium(III) (ClTTDPzGa) have been optimized at the level B3LYP with basis sets 6-31G*, 6-311++G**, and cc-pVTZ, and the structures have been compared with those obtained by X-ray diffraction. Vibrational frequencies have been calculated for all six molecules at all basis sets combinations, except B3LYP/cc-pVTZ. These calculations predict that all molecules have C 4 v symmetry with the metal atom above the plane defined by the four inner cavity N atoms and an almost planar macrocycle. The most important structure parameters (GED|B3LYP/cc-pVTZ) are h (height of the metal atom above the inner cavity) h = 50.3(32)|44.9 pm, r(Al-Cl) = 214.5(16)|217.4 pm, r(Al-N) = 197.6(9)|198.7 pm, angle(Cl-Al-N) = 104.8(9)|103.1 degrees, angle(Al-N-C) = 124.2(7)|125.9 degrees for ClPcAl, and the corresponding values for ClPcGa are h = 53.1(28)|50.2 pm, r(Ga-Cl) = 218.9(14)|222.3 pm, r(Ga-N) = 200.6(8)|202.6 pm, angle(Cl-Ga-N) = 105.4(8)|104.3 degrees, angle(Ga-N-C) = 123.8(8)|125.0 degrees. Parenthesized values are estimated error limits defined as 2.5(sigma(2)(lsq) + (0.001 x r)(2))(1/2) for distances and 2.5sigma(lsq) for angles. The title compounds are all flexible molecules with about five vibrational frequencies below 100 cm(-1).