Superlative Scaffold of 1,2,4-Triazole Derivative of Glycine Steering Linear Chain to a Chiral Helicate

Abstract

Solvothermal and classical synthesis with an identical recipe involving 4H-1,2,4-triazol-4-yl acetic acid (HL1) and CdCl2 afforded two-dimensional (2D) (1) and one-dimensional (2) coordination polymers, respectively. Hexagonal plate-like crystals of [Cd2(L1)2Cl2] (1), which crystallize in the chiral orthorhombic space group (P212121), were obtained in high yield. The 1,2,4-triazole-4-yl acetate (L1) ligand, which has a significant kink in the spacer, leads to the formation of a CdII complex displaying a 2D single-stranded helical array. The pitch height of the helix is equal to the length of the crystallographic a axis (7.579 Å) which comprises two cadmium atoms and two ligands. Solid-state emission of 1 shows a strong emission band around 465 nm with photoexcitation at 290 nm. Mercury porosimetry measurements reveal pore size distribution with a diameter of 80, 10, and 1 μm. BET shows no preference for N2(g) but a low H2(g) adsorption of 4 cm3/g. Complex 1, which is constituted by a “soft” nonaromatic network that begins to collapse around 170 °C, was subjected to controlled pyrolysis to produce CdO with morphology and phase selectivity. Texture of the thus obtained pure cubic phase of CdO (β-form) was further tuned with the regulation of the annealing temperature. Crystals of rectangular blocks of [Cd(HL1L1)Cl]·2H2O (2), which were formed in small quantity, feature a centrosymmetric, monoclinic space group (P21/c). Their crystal structure reveals a one-dimensional linear chain where Cd atoms are connected by a triple bridge made up of one μ-chloride and two μ-N1,N2-1,2,4-triazole HL1 and L1. The coordination polymer charge is balanced by both chloride and the carboxylate group of L1.