Cu(II)-Based Molecular Hexagons Forming Honeycomb-like Networks Exhibit High Electrical Conductivity.

Four new Cu(II)-based hexagonal complexes with the metallomacrocycle formulae [Cu 6 (5-nip) 6 (3-py) 6 (H 2 O) 12 ] ( 1 ), [Cu 6 (5-nip) 6 (3-Clpy) 6 (H 2 O) 12 ] ( 2 ), [Cu 6 (5-nip) 6 (3-Brpy) 6 (H 2 O) 12 ] ( 3 ), and [Cu 6 (5-nip) 6 (3-Ipy) 6 (H 2 O) 12 ] ( 4 ) have been synthesized using 5-nitroisophthalic acid (H 2 5-nip) and pyridine (py)/3-halopyridine (3-Xpy; X = Cl, Br, and I) ligands. The structural features and supramolecular interactions of compounds 1 - 4 have been investigated using the single-crystal X-ray diffraction (SCXRD) technique. Interestingly, the hexagonal complexes undergo hydrogen bonding and π···π stacking interactions to form fascinating two-dimensional (2D) honeycomb-like structures. The synthesized complexes exhibit high electrical conductivity, arising from charge transport through space via π···π contacts. However, complexes containing 3-Brpy ( 3 ) and 3-Ipy ( 4 ) exhibit photosensitivity due to the presence of halogens with a larger size and lower ionization energy. The conductivity results are also in accordance with the theoretical prediction calculated by density functional theory (DFT) study.