Two tartratoborates with hybrid anionic groups from unusual condensation reactions

Abstract

Two novel tartratoborates, namely, K₂[(C₄H₂O₆)(B₃O₄H)](H₂O) (1) and KCu₂[(C₄H₂O₆)₂B](H₂O)_2.5 (2), have been successfully synthesized by solvothermal reactions. They feature different kinds of structural types based on hybrid borate–tartrate motifs. The structure of compound 1 features a 3D network composed of novel [(C₄H₂O₆)₂(B₃O₄H)₂]⁴⁻ anionic groups interconnected by K⁺ cations. The [(C₄H₂O₆)₂(B₃O₄H)₂]⁴⁻ anion was formed by the condensation of two (B₃O₈H)⁶⁻ groups and two tartrate anions, and such condensation reaction has never been reported previously. Compound 2 exhibits a novel 3D network structure in which 2D {Cu₂[(C₄H₂O₆)₂B](H₂O)₂}⁻ layers are further interconnected via K⁺ ions. The [(C₄H₂O₆)₂B]⁵⁻ anion was formed by the condensation of two tartrate anions with a B(OH)₄⁻ unit. Magnetic measurements reveal a dominant antiferromagnetic interaction between neighboring Cu²⁺ ions in compound 2. Furthermore, UV-vis and infrared spectra and thermal analyses were also performed.