A novel strategy to construct Janus metallamacrocycles with both a Ru–arene face and an imidazolium face.

The bottom-up construction of highly functional metallamacrocycles from simple building blocks is a challenge of much current interest. We have used solvothermal reactions of a bifunctional p-bitmb ligand with [Ru(arene)X2]2 in CH2Cl2 or CH2Br2 to generate the novel mononuclear metallamacrocyclic [RuX(arene)L2CH2]X3 complexes 1–3 (1, arene = p-cym, X = Cl; 2, arene = bip, X = Cl; 3, arene = p-cym, X = Br), which were characterized by various techniques. These complexes are “bowl-like” and have two faces: one coordinative Ru centre (arene)Ru(N,N)X bridged by L (L = 1,4-bis(imidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene, p-bitmb) to a dipositive bis-imidazolinium centre. Cl− or Br− anions can be trapped inside the cavity of the “bowl-like” structure, forming H-bonds with the backbone. Experimental (NMR and ESI-MS) and computational (DFT calculations) studies show that the source of the bridging –CH2– group is the dihalogenated solvent (CH2Cl2 or CH2Br2) that links the two arms of an initially formed non-cyclic complex (arene)RuX2L2 by a mechanism of nucleophilic substitution. Optimization of the reaction conditions afforded the macrocyclic complexes in almost quantitative yields. The applications of these complexes as anti-proliferative agents towards cancer cells and for selective anion sensing have been explored. [ABSTRACT FROM AUTHOR]