Hydrogen Bonding Assisted Construction of Graphite-like Deep-UV Optical Materials with Two Types of Parallel π-Conjugated Units

Abstract

Three new formic-borates Na(COOH)[B(OH)3](H2O)2 (1), K3(COOH)3[B(OH)3]2 (2), and (HCOOH)3[B(OH)3]2·3H2O (3), containing two types of planar π-conjugated BO3 and HCOO groups, have been synthesized via systematic investigations in A–HCOO–BO3 (A = alkali metal) systems using hydrothermal methods. Compounds 1 and 2 crystallize in the centrosymmetric space groups Pnma and C2/c, and compound 3 crystallizes in the non-centrosymmetric space groups Pn, respectively. All the three titled compounds exhibited three-dimensional (3-D) frameworks with a parallel arrangement of B(OH)3 and HCOO planar π-conjugated units through hydrogen bonding assisted construction. Particularly, compounds 2 and 3 showed a graphite-like layer structure. In compound 1, the Na(COOH)[B(OH)3] chains are connected with water molecules by hydrogen bonding to form the 3-D framework. In 2, graphite-like {(COOH)3[B(OH)3]2}3– layers composed of HCOO and B(OH)3 groups construct the 3-D framework through the bridging of charge-balance cations K+ loc...