Synthesis and characterization of s-fac-[Co(dien)(2)](4-np)(3)(4-npH)center dot 2H(2)O containing symmetric, [4-np center dot center dot center dot H center dot center dot center dot 4-np](-) and unsymmetric, [4-np center dot center dot center dot H center dot center dot center dot 4-np(-)]( )dimers of 4-nitrophenolate (4-np(-))

摘要

Symmetric [4-np center dot center dot center dot H center dot center dot center dot 4-np](-) and unsymmetric [4-np center dot center dot center dot H center dot center dot center dot 4-np(-)] dimers of 4-np - have been isolated in s-fac-Ko(dien)(2)](4-nP)(3)(4-npH)center dot 2H(2)O (dien = diethylenetriamine) using a one pot synthesis. The crystal structure of the title complex revealed a strong network of H-bonding interactions which lead to the formation of layers of [H(4-np)(2)](-) (symmetric and unsymmetric), s-fac-[Co(dien)(2)](3+) and water molecules. These layers formed their respective columns and the intermolecular cohesion of 4-npH within the columns of the 4-np(-) ions is achieved via nitro-pi and pi-pi stacking interactions. Water also played a dominant role in stabilizing the structure, in which the H-O-H center dot center dot center dot O (4-np(-)) interaction is weaker than [4-np center dot center dot center dot H center dot center dot center dot 4-np](-), but stronger than the N-H center dot center dot center dot O (4-np)(-) and N-H (dien)center dot center dot center dot-H-O interactions. The H-bond present in the symmetric dimer is the strongest one, having an O center dot center dot center dot O contact distance of 2.433(3) angstrom. The presence of the s-fac-isomer of the cation is also supported by IR and H-1, C-13 and 2D H-1-C-13 NMR spectroscopy. The XRD pattern of the product (bulk) was also determined and it shows the presence of a single phase. The binding capacity (log beta = 27.101 +/- 0.06) of [Co(dien)(2)](3+) with the 4-np(-) was determined by UV-vis spectroscopic titrations and the ionic behaviour of the complex was confirmed by molar conductance measurements at infinite dilution (lambda(o) = 800 S cm(2) mol(-1)). (C) 2019 Elsevier Ltd. All rights reserved.