Sequential Assembly and Stabilization of Cu₆S₆ Octahedral Clusters in NaCl-, NiAs-, and CdI₂-Related Structures and Their Utility toward Thermochromism and Multicomponent Hantzsch Reaction

Abstract

Seven new inorganic–organic coordination polymer compounds have been synthesized and their structures are determined by single-crystal structure determination. The compounds were prepared by the sequential assembly of a [Cu6(mna)6]6– moiety in the presence of a Mn salt and a secondary amine ligand. Of the seven compounds, [{Cu6(mna)6}Mn3(H2O)(H2O)1.5]·5.5H2O (I), [{Cu6(mna)6}Mn3(H2O)(Im)1.5]·3.5H2O (Ia), [{Cu6(mna)6}{Mn(BPY)(H2O)}2{Mn(H2O)4}]·2H2O (III), and [{Cu6(mna)6}{Mn(BPE)0.5(H2O)2}2{Mn(BPE)(H2O)2}] (IV) have a three-dimensional structure, whereas [{Cu6(mna)4.5(Hmna)1.5}{Mn(BPA)(H2O)2}{Mn(H2O)}]{Mn0.25(H2O)3}·7H2O (II), [{Cu6(mna)6}{Mn(4-BPDB)0.5H2O}{Mn(H2O)2}].{Mn(H2O)6}·6H2O (V), and [{Cu6(mna)4(Hmna)2}·{Mn(H2O)3}2]·(4-APY)2·6H2O (VI) have a two-dimensional structure. Some of the prepared compounds exhibit structures that closely resemble the classical inorganic structures, such as NaCl (Ia, III), NiAs (I), and CdI2 (IV and VI). The stabilization of such simple structures from the assembly of octahedral Cu6S6 clusters and different Mn species and aromatic nitrogen-containing ligands suggests the subtle interplay between the constituent reactants. The compounds were examined for the multicomponent Hantzsch reaction, which gave the product in good yields. The compounds, II and VI, on heating to 70 °C change color reversibly from pale yellow to deep red, which suggests the possible use of these compounds as thermochromic materials. The present study suggests that the Cu6S6 octahedral clusters can be assembled into structures that resemble classical inorganic structures.