Synthesis and structural characterization of centrosymmetric multinuclear nickel(II) complexes with neutral tetradentate N6-ligand

• Main Authors: Subramaniam, Jeevithra Dewi, Lee, Sze Koon, Chinapang, Pondchanok, Praneeth, Vijayendran K. K., Okamura, Masaya, Kondo, Mio, Masaoka, Shigeyuki, Woi, Pei Meng
• Format: Article
• Published: Springer 2021
• Subjects: QD Chemistry; TP Chemical technology
• Online Access: http://eprints.um.edu.my/34122/

A neutral tetradentate ligand L1 L1 = 3,6-bis(pyrazol-1-yl)-pyridazine] reacts with Ni(ClO4)(2)center dot 6H(2)O and undergoes counterion exchange with PF6- to give di- and tetranuclear complexes Ni-2(L1)(2)(CH3CN)(4)](PF6)(4)center dot 4H(2)O (1) and Ni-4(L1)(4)(mu-OH)(4)](ClO4)(4)center dot 2H(2)O (2), respectively. The presence of 1,8-diazabicyclo5.4.0]undec-7-ene (DBU) as base controls the nuclearity of the complex formation. Both complexes were structurally characterized by physicochemical and spectroscopic techniques. Their crystal structures revealed that both complexes are centrosymmetric and adopt slightly distorted octahedral geometry. Complex 1 crystallizes in monoclinic space group C2/c as the Ni(II) center is octahedrally bound to L1 in a trans-isomer arrangement. Complex 2 crystallizes in tetragonal space group I4(1)/amd with four L1 and four hydroxy bridging ligands linked to Ni(II) center in cis-isomer arrangement. Cyclic voltammograms of complexes 1 and 2 were measured under Ar and CO2. Under CO2, the quasireversible peaks of both complexes become irreversible and a current enhancement occurs under reduction.