Synthesis and DFT calculations of oxido and phenylimido-rhenium(V) complexes incorporating the N, O donor ligand 2-[(2-hydroxyethylimino)methyl]phenol

Abstract

The reactions of equimolar amounts of trans-[ReOC1₃(PPh₃)₂] or trans-[Re(NPh)(PPh₃)₂Cl₃] with a Schiff base formed by condensation of 2-hydroxy-4-methoxybenzaldehyde and ethanolamine (H₂L) result in the formation of cis-[ReO(HL)PPh₃Cl₂] (1a) and trans-[Re(NPh)(HL)(PPh₃)Cl₂] (2b), respectively, in good yields. 1a and 2b have been characterized by a range of spectroscopic and analytical techniques. The X-ray crystal structures of 1a and 2b reveal that 1a is an octahedral cis-Cl,Cl oxorhenium(V) complex, while 2b is a trans-Cl,Cl phenylimidorhenium(V) complex. The complexes are weakly emissive at room temperature with quantum yields of 10⁻⁴. Density functional theory calculations of the electronic properties of the complexes were performed and are in agreement with the experimental results. The complexes display quasi-reversible Re(V)/Re(VI) redox couples in acetonitrile. There is reasonable agreement between the experimental and calculated redox potentials of 1a and 2b.

Keywords:

• Rhenium
• Schiff-base ligand
• fluorescence
• electrochemistry
• density functional theory

Disclosure statement

No potential conflict of interest was reported by the authors.

Funding

Financial support [F. No. SR/FT/CS-75/2010] received from the SERB under Department of Science and Technology (DST), India is gratefully acknowledged. J.P. Naskar sincerely acknowledges the financial support received from the University Grants Commission (UGC), New Delhi, India [F. No. 41-220/2012 (SR)]. P. Saha sincerely acknowledges the research fellowship received from the UGC, India.