Effects of -oxidation on the molecular and crystal structures and properties of isocinchomeronic acid, its metal complexes and their supramolecular architectures: experimental, CSD survey, solution and theoretical approaches

Nine coordination complexes and polymer (M/L/X) based on Co, Ni, Zn, Cu (M), pyridine- N -oxide-2,5-dicarboxylic acid (H 2 pydco) (L) and either isonicotinamide (Ina), piperazine (pipz), 2,2-bipyridine (bipy) and 1,10-phenanthroline (phen) (X) were synthesized and characterized by elemental analyses, infrared spectroscopy and single crystal X-ray diffraction. The resulting empirical formulae of the prepared complexes are [Co(H 2 O) 6 ][Co(pydco) 2 (H 2 O) 2 ]2H 2 O ( 1 ), [M(pydco)(H 2 O) 4 ] 2 [M = Co ( 2 ), Ni ( 3 ), Zn ( 4 )], [Co(pydco)(bipy)(H 2 O) 2 ]4H 2 O ( 5 ), [Co(pydco)(phen)(H 2 O) 2 ]5.135(H 2 O)0.18(EtOH) ( 6 ), [Cu(Hpydco)(bipy)Cl]2H 2 O ( 7 ), [Cu(Hpydco)(bipy)Cl] 2 2H 2 O ( 8 ), and {[AgCu(H 2 O) 2 (phen)(pydco)]NO 3 } n ( 9 ). With the exception of 9 , which forms an extended structure via multiple coordination modes, all the complexes contain (H)pydco as a bidentate ligand coordinated to the metal ion via the N -oxide and the adjacent carboxylate group oxygen atom, creating a chelate ring. The metal centers exhibit either distorted octahedral ( 16 ) or square pyramidal ( 79 ) geometry. Our results demonstrate that, when acting cooperatively, non-covalent interactions such as XHO hydrogen bonds (X = O, N, C), CO and stacking represent driving forces for the selection of different three-dimensional structures. Moreover, in compounds 24 , 1D supramolecular chains are formed where Ohole interactions are established, which unexpectedly involve the non-coordinated carboxylate group. The non-covalent interaction (NCI) plot index analysis reveals the existence of the Ohole interactions that have been evaluated using DFT calculations. The Cremer and Pople ring puckering parameters are also investigated. The complexation reactions of these molecules with M were investigated by solution studies. The stoichiometry of the most abundant species in the solution was very close to the corresponding crystals. Finally, the effect of N -oxidation on the geometry of complexes has been also studied using the Cambridge Structural Database. It shows that complexes containing N -oxidized H 2 pydc are very rare. A series of new coordination complexes bearing H 2 pydco, an O-donor ligand, were synthesized and compared to corresponding complexes with H 2 pydc. The molecular and supramolecular structures were investigated using crystallography, solution phase and high level DFT studies.