New Examples of Metal Coordination Architectures of 3,3′,4,4′‐Biphenyltetracarboxylic Acid – Syntheses, Crystal Structures, and Physical Properties

Four new metal‐organic frameworks [Cu 2 (2,2′‐bipy) 2 (ox)(H 2 O) 2 ]·(H 2 bptc) ( 1 ), [Cu(bptc) 0.5 (phen)(H 2 O)]·H 2 O ( 2 ), Co 2 (bptc)(bmb) 1.5 ( 3 ) and [Cd 2 (bptc) (bmb)]·3H 2 O ( 4 ) (H 4 bptc = 3,3′,4,4′‐biphenyltetracarboxylic acid, ox = oxalate, phen = 1,10‐phenanthroline, 2,2′‐bipy = 2,2′‐bipyridine and bmb = 4,4′‐bis((1H‐imidazol‐1‐yl)methyl)biphenyl), were obtained by reactions of the corresponding metal salts with H 4 bptc and N‐containing auxiliary ligands and their structures were determined by single‐crystal X‐ray diffraction. The results reveal that 1 has a 0‐D structure consisting of discrete ionic entities, while 2 features a 1‐D ladder structure. Additionally, there exist π‐π stacking and intermolecular hydrogen‐bonding interactions in 1 and 2 , respectively, forming 3‐D supramolecular structures. In 3 ‐ 4 , undulating 2‐D metal‐bptc layer structures are formed with two different coordination modes of bptc carboxylate groups, respectively, which are further extended by bmb into 3‐D structures. Magnetic properties of 1 and 3 have been studied. The photoluminescence property of 4 has also been investigated. Moreover, nonlinear optical measurements showed that 4 displayed a second‐harmonic‐generation (SHG) response of 0.7 times of that for urea.