Journal of Coordination Chemistry, 2013 Vol. 66, No. 7, 1178-1188, http://dx.d0i.0rg/l0.1080/00958972.201 l,. An oxorhenium(V) Schiff-base complex: synthesis, structure, spectroscopic characterization, electrochemistry, and DFT calculations SMITA MAJUMDERf, JNAN PRAKASH NASKARÍ, SNEHASIS BANERJEE§, ARNAB BHATTACHARYAt, PARTHA MITRAf and SHUBHAMOY CHOWDHURY*t jDepartment of Chemistry Tripura, University Suryamaninagar, India ^Department of Chemistry, Inorganic Chemistry Section Jadavpur University, Kolkata, India §W.B. Govemment College of Engineering and Leather Technology, Kolkata, India ^Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata, India (Received 22 June 2012; in final form 13 November 2012) Reaction of the Schiff base 2-[(2-hydroxyethylimino)methyl]phenol (H2L) with trans- ReOCl3(PPh3)2 in 1 : I M ratio in dichloromethane gives [ReOCl2(HL)(PPh3)] (1) in substantial yield. The compound has been characterized by C, H, and N microanalyses, IR, UV-Vis, ' H NMR, and ESI-MS spectra. The X-ray crystal structure of the title compound has been determined. The structure reveals that it is an octahedral cis-Cl, Cl oxorhenium(V) complex where the relative positions of the two chlorides are eis. 1 crystallizes in the monoclinic space group Pl^ln with 0=14.198(2), 0=10.970(1), c=18.258(l) A, /9= 111.83(1)°, K=2640.0(3) A^ and Z=4. Electro- chemical studies in dichloromethane show Re(V) to Re(Vl) oxidation at 1.51 V along with two successive reductions - Re(V) to Re(IV) and Re(IV) to Re(III) at -0.66 V and -1.03 V versus Ag/AgCl, respectively. Geometry optimization of 1 vis-à-vis its trans analog, trans-Cl, Cl complex 2, has been performed at the level of density functional theory; 2 is more stable than 1 by 2kcalM~'. Keywords: Oxorhenium(V) complex; Schiff-base ligand; Electrochemistry; DFT calculation 1. Introduction Coordination chemistry of rhenium and technetium is of considerable interest due to the use of '^^"^^Re and ' ' " T c as therapeutic agents and diagnostic imaging agents, respec- tively, in nuclear medicine [1-5]. ''™Tc is widely used in nuclear medicine, while '^''' '^^Re has the potential to be used in tumor specific treatments. Rhenium involves several oxidation states ranging fi-om - I to VII. Oxidation of Re(V) complexes to Re(VII) is a prerequisite step in the catalytic cycle of oxygen atom transfer (OAT) [6]. The catalytic aspects of mono- and dinuclear methyloxorhenium(V) complexes as prospective candidates for OAT reactions have been extensively investigated [7, 8]. Thus, there is continuing interest in fundamental knowledge about the structure, spectroscopic properties, and redox *Corresponding author. Email: s.chowdhury@tripurauniv.in © 2013 Taylor & Francis