A 3D heteropolyoxoniobate framework based on heart-shaped {Te₂Nb₁₉O₆₀} clusters with proton conductivity property

A 3D tellurium-substituted heteropolyoxoniobate framework H5K3Na[Cu(en)(2)](2)[Cu(en)(0.75)(H2O)(2.5)]{[(Te2Nb19O58)(mu(3)-OH)(2)]}24H(2)O (1, en = ethylenediamine) with a 6-connected pcu topology is built from heart-shaped {Te2Nb19O60} clusters and copper complexes. The {Te2Nb19O60} cluster represents the new tellurniobate structure type with a 19-nuclearity Nb cluster. It consists of two new monovacant Lindqvist {Nb5O19} clusters, one boat-shaped {Nb9O32} cluster and two TeO32- anions. The {Te2Nb19O60} polyanions are interlinked by [Cu(en)(2)](2+) complexes into a 2D (4, 4) grid-like layer containing rhombic sheets. The Cu2+ supports the adjacent layers through Te-O-Cu-O-Te- bonds to form a three-dimensional heteropolyoxoniobate framework with 1D channels. This compound exhibits good chemical and solvent stability and proton conductivity, with a conductivity of 7.9 x 10(-3) S cm(-1) at 85 degrees C under 98% RH.