Temperature-controlled 1D helical and discrete Er(III) complexes based on benzimidazole-5,6-dicarboxylic acid

The reaction between ErCl3·6H2O and H2bmdc (H2bmdc = benzimidazole-5,6-dicarboxylic acid) produced two distinct complexes: 1D helical complex {[Er(Hbmdc)(bmdc)(H2O)3]·3H2O}n (1) obtained under hydrothermal condition at 160 °C and discrete complex [Er2(Hbmdc)2(bmdc)2(H2O)8]·8H2O (2) under ambient temperature, evaporated from the mother liquor of 1. The crystal structures of the complexes were determined by X-ray single-crystal diffraction. Through comparison of complexes 1 and 2, we found that enhanced temperature favors the formation of higher dimensional products and lower amount of coordinated water. Both complexes are characterized by IR, elemental analysis, X-ray powder diffraction and thermogravimetric analysis.