Synthesis and Characterization of Oxovanadium(IV) Complexes with 2,2’,2”,6-Terpyridine and 2,6-Bis(pyrazol-3-yl)pyridine Ligands
Fakhrotun Nisa (a*), Djulia Onggo (a)
a) Department of Chemistry, Bandung Institute of Technology
Jalan Ganesha 10, Bandung 40132, Indonesia
*nfakhrotun[at]gmail.com
Abstract
Oxovanadium(IV) complexes with nitrogen donor ligand have been reported such as [VO(bpy)₂]SO₄ and [VO(phen)₂]SO₄. Generally, the complexes used bidentate N,N ligands. On the other side, tridentate ligands can increase the stability of complexes due to chelate effect. So in this study, two vanadyl complexes with nitrogen donor tridentate ligands have been synthesized namely 2,2,2",6-terpyridine and 2,6-bis(pyrazol-3-yl)pyridine. The difference between the two ligands is the two pyridine rings at terpyridine replaced by the pyrazol ring. These complexes have been synthesized from VOSO₄ and the ligand with 1:1 mole ratio. The dark green and light blue solid products obtained with 84% and 80% yields. Elemental analysis result showed 44.62% C, 3.07% H, 10.99% N, and 7.55% S (calculated: 44.41% C, 3.20% H, 10.36% N, and 7.89% S) indicating the formula of C₁₅H₁₁N₃O₅SV.½H₂O or [VO-terpy]SO₄.½H₂O. The other result is 31.12% C, 3.31% H, 16.51% N, and 7,46% S (calculated: 30.84% C, 3.50 % H, 16.35% N, and 7.47% S) for C₁₁H₉N₅O₅SV.3H₂O or [VO-bpp]SO₄.3H₂O. Both oxovanadium(IV) complexes are 2:2 electrolytes based on molar conductivity values of 238 and 212 S cm² mol⁻¹ respectively. The appearance of 150 amu and 139 amu peaks in the ESI-MS spectra were giving evidence of cationic complexes. Thermal stability of complexes were analyzed by TG. These complexes are paramagnetic because their magnetic moment values of 1.73 BM and 1.69 BM due to the presence of one unpaired electron. Interestingly, [VO-bpp]SO₄.2½H₂O complex has a thermochromic effect.
Keywords: Vanadyl complexes; Tridentate ligand; Terpyridine ligand; Bpp ligand
Topic: Minerals and Complex Materials