Polarizability of Pyruvate Anion in Small Water Clusters

Pyruvate anion is important in a broad array of physicochemical processes ranging from glucose homeostasis to atmospheric reactions. However, the electronic polarizability of the moiety has not been investigated extensively. We present theoretical results from electronic structure calculations on the static and dynamic polarizability of microhydrated pyruvate anions. These investigations were carried out with the CH3COCOO[Formula: see text]n H2O clusters ([Formula: see text]–9) to mimic microhydration conditions. These density functional theory calculations were carried out at the B3LYP/aug-cc-PVTZ level to uncover the optimal geometry of the anion water cluster. Sadlej basis set functions with the B3LYP functional were used to calculate the static and dynamic polarizabilities. Multiple simulated annealing simulations were carried out to discover additional low-lying minima. It is observed that the electronic polarizability varies linearly with the size of the hydrated cluster. Expressions that describe the relationship between the dynamic polarizability and the field frequency are provided for each cluster.

Synthesis, revised crystal structures, and refractive indices of ABW-type CsMTiO4 (M = Al, Fe, Ga) and ANA-type CsTi1.10Si1.90O6.50, and the determination of the electronic polarizability of 4-coordinated Ti4+

Single crystals of ABW-type CsAlTiO4 (CAT), CsFeTiO4 (CFT), CsGaTiO4 (CGT), and ANA-type CsTi1.1Si1.9O6.5 (CST) were grown and characterized by electron microprobe analyses, single-crystal X-ray diffraction, thermal analyses, and spindle-stage optical investigations to determine the electronic polarizability of 4-coordinated Ti4+, α([4]Ti4+). The crystal structure of CAT was confirmed to crystallize in the highest possible topological symmetry Imma (a = 8.9677(2) Å, b = 5.7322(1) Å, c = 9.9612(3) Å) with tetrahedrally coordinated Al and Ti equally distributed on Wyckoff position 8i. Twinning by reticular merohedry with a twin index of 2 was observed for most of the crystals resulting in a hexagonal twin lattice (a = 11.487(3) Å, c = 8.968(2) Å) with Laue symmetry 6/mmm. Refractive indices measured by immersion methods on an untwinned specimen are nx = 1.716(5), ny = 1.725(2), and nz = 1.727(1) with 2Vz = 127.1(6)°. The diffraction patterns of CFT and CGT clearly showed superstructure reflections causing a symmetry lowering of index 4 with a transformation according to 2a, b, c from Imma to Pmab with a = 18.3054(7) Å, b = 5.8083(2) Å, c = 9.9938(4) Å for CFT, and a = 18.2921(6) Å, b = 5.7636(2) Å, c = 9.9210(3) Å for CGT. Refractive indices for CGT are nx = 1.750(3), ny = 1.772(3), and nz = 1.776(2) with 2Vz = 132(1)°. The crystal structure of the ANA-type CsTi1.1Si1.9O6.5 was confirmed to crystallize in space group Ia$\overline{3}$d (a = 13.8333(4) Å). The extra 0.5 O atoms are needed for charge compensation and to allow the sum of electronic polarizabilities to give a total electronic polarizability calculated from the refractive index n = 1.718(4). The electronic polarizability of [4]Ti4+ was calculated from the difference between the observed total polarizabilities (derived from the mean refractive indices of CAT and CGT) and the sum of electronic polarizabilities of cations and anions omitting the polarizability of Ti resulting in α([4]Ti4+) = 5.15(5) Å3.