Spectrochimica Acta Part A 58 (2002) 2771 – 2778 Stereochemistry of new nitrogen containing heterocyclic aldehyde. IX. Spectroscopic studies on novel mixed-ligand complexes of Rh(III) A.Z. El-Sonbati a, *, A.A. El-Bindary a , A.A. Al-Sarawy b a Chemistry Department, Faculty of Science (Demiatta), Mansoura Uniersity, Demiatta, Egypt b Department of Math. and Phys. Sciences, Faculty of Engineering, Mansoura Uniersity, Mansoura, Egypt Received 25 October 2001; received in revised form 8 December 2001; accepted 9 January 2002 Abstract Mono, bis and tris complexes of rhodium(III) oxine (systematic name 8-hydroxy-7-quinolinecarboxaldehyde) and mixed ligand have been prepared. The amine exchange reaction of coordinated Schiff base in these complexes has also been carried out, which gives symmetrical tetradentate Schiff base complexes. The complexes are characterized by elemental and thermal analysis, IR, magnetic and electronic spectral analysis methods were also employed as well as conductivity measurements. An octahedral structure is proposed for all the new complexes in which chloride is attached to the metal ion in 1:1; 1:2 (metal:ligand) ratio. The spectral data were utilized to compute the important ligand field parameter B,  and Dq. The B -values suggest a strong covalency in the metal-ligand -bond and the Dq-values indicate a medium strong ligand field. 1 H NMR spectra show that the tris (ligand) complex is cis isomer. IR spectra show that the ligand is mono-basic bidentate. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Amine exchange reaction; Mixed ligand complexes; Racah interelectronic repulsion parameter www.elsevier.com/locate/saa 1. Introduction Studies on the complexing behaviour of biolog- ically active ligands containing quinoline group have been the subject of investigation in our laboratory [1 – 10]. Increasing evidence on the bio- logical relevance of rhodium has been ac- cumulated during the last year [11–13] and its essentiality, distribution and toxicity as well as its biological and pharmacologic activity are areas of great interest. Nevertheless, the role of rhodium in higher organisms is still unclear. As part of our studies about simple inorganic models of interest for the development of bioinor- ganic chemistry of rhodium, El-Sonbati and El- Bindary [9–11] have started investigations on Rh(III) complexes with 8-hydroxy-7-quinolinecar- boxaldehyde (oxine) (LH) which appear to be * Corresponding author. Fax: +20-57-403-868 E-mail address: elsonbatisch@yahoo.com (A.Z. El-Sonbati). 1386-1425/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S1386-1425(02)00021-5