Three pairs of Pb(II), Cd(II) and Cu(II) enantiomeric coordination compounds based on D-(−)- and L-(+) -4-Hydroxyphenylglycine: Synthesis, structures and properties

Abstract

Three pairs of stable chiral coordination compounds [Pb(D-hpg)2(bpe)2]⋅(NO3)2 (1), [Pb(L-hpg)2(bpe)2]⋅(NO3)2 (2); {[Cd (D-hpg) (bpe) (H2O)]⋅(NO3)⋅(H2O)}n (3), {[Cd(L-hpg) (bpe) (H2O)] ⋅ (NO3)⋅(H2O)}n (4); {[Cu2 (D-hpg) 2(bpe) (H2O)2]⋅(NO3)2·H2O}n (5), {[Cu2 (L-hpg)2 (bpe) (H2O)2]⋅(NO3)2·H2O}n (6) (D-Hhpg = d-(−)-4-Hydroxyphenylglycine, l-Hhpg = l-(+)-4-Hydroxyphenylglycine, bpe = 1,2-bis(4-pyridyl)ethane) have been successfully synthesized. Their structures were determined by single-crystal X-ray diffraction analysis and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction and circular dichroism. Compounds 1 and 2 feature 0D molecule structures, compounds 3 and 4 are 2D rectangular grid networks and compounds 5 and 6 exhibit 2D hexagonal grid networks with an ABAB stacking sequence. Compounds 1–6 are further extended into 3D supramolecular architectures through hydrogen-bonding interactions. Our results highlight that the modulation of coordination polymers with different structures can be accomplish by selecting the center metal of different electronic structures. Luminescent properties of compounds 1 and 2 were investigated at room temperature. 1 and 2 show similar selectivity toward Fe3+ions through luminescent quenching in aqueous solution. Moreover, the electrochemical behaviors of compounds 5 and 6 were further studied by cyclic voltammetry, indicating a surface-controlled electrochemical process.