Potential multifunctional anti-cancer metal complexes. I. Synthesis and x-ray structural studies of some dinuclear rhodium(II) carboxylate complexes with diamine-substituted acridine ligands in terminal coordination positions

Abstract

The preparations are reported of [Rh(RCO 2) 2L] 2 [where R = CH 3, C 2H 5, and CH 3OCH 2; L = 6-chloro-2-methoxy-9-[2(NR′ 2)ethyl]aminoacridine (R′ = H, CH 3)]. X-ray structural studies have been carried out on two of the compounds [ R = C 2H 5, R′ = H, (1); R = CH 3, R′ = CH 3, ( 2)]. Compound 1 is monoclinic, space group C2/ c, with a = 20.864(11), b = 15.736(4), c = 14.402(4) Å, β = 93.14(4)°, V = 4721 Å 3, and Z = 4; 2 is monoclinic, space group P2 1/ n, a = 8.861(2), b = 23.089(10), c = 12.014(2) Å, β = 105.84(2)°, V = 2365 Å 3, and Z = 2. Both compounds comprise the standard dinuclear rhodium(II) carboxylate unit with the substituted acridine ligands coordinated to rhodium in the axial positions, via the NH 2 group nitrogen in 1 and the N(CH 3) 2 nitrogen in 2. The dimethyl substitution on the tertiary amine group in 2, and an associated conformational change in the diamine chain, result in an increased separation of the acridine ligand from the metal centre. There is a pronounced acridine base stacking in 1 but not in 2.