Supramolecular Structures with the 2‐Propyl‐4,5‐dicarboxy‐1H‐imidazole Ligand: Hydrothermal Synthesis, Structures, and Photoluminescence

Self-assembly of the rigid organic ligand 2-propyl-4,5-dicarboxy-1H-imidazole (L) with different metal ions (Zn2+, Ni2+, Cu2+, Cd2+) led to four new complexes, namely, [M(L)(phen)] [M = Zn (1); Ni (2); Cd (3)] and [Cu(L)(4)] (phen = 1,10-phenanthroline). Their structures were determined by single-crystal X-ray diffraction analyses, and they were further characterized by elemental analysis, IR spectroscopy, and thermogravimetric analysis. Whereas compounds 1, 2, and 3 are discrete units, hydrogen-bonding interactions play a vital role in these complexes. Compounds 1 and 2 form one-dimensional (1D) and two-dimensional (2D) structures through hydrogen-bondinginteractions with helical character. In 1, the hydrogen bonds (O–H···O) alternately bridge the MII cations of the discrete units to form a one-dimensional (1D) infinite helical chain. Complex 2 forms a 2D helical layer through parallel hydrogen bonds (N/O–H···O/N) between two adjacent helical chains. In 3, the hydrogen bonds (N–H···O) connect adjacent discrete units into a ten-membered ring with extension into a one-dimensional double-chain supramolecular structure. Complex 4 is a two-dimensional gridlike (4,4) topological layer which is extended to a 3D network by hydrogen bonding. The solid-state fluorescence spectrum of complex 3 was determined.