Synthesis and Recognition Properties of a Ruthenium(II)−Bis(zinc) Cyclic Porphyrin Trimer

2000-11-29T00:00:00Z (GMT) by Simon J. Webb Jeremy K. M. Sanders
A series of cyclic metalloporphyrin trimers containing one Ru(II)−CO porphyrin center are synthesized. A stepwise convergent route is used to synthesize Ru(CO)Zn22·Py3T, where tripyridyltriazine (Py3T) templates the formation of the trimer and forces the CO group to the outside of the cavity. Three mixed-metal trimers, Ru(CO)Zn22, Ru(CO)Ni22, and Ru(CO)Mg22, are synthesized from Ru(CO)Zn22·Py3T and are characterized by NMR, UV−visible, and fluorescence spectroscopy. The Ru(CO)Zn22 trimer is found to bind Py3T very tightly (K ≈ 1012 M-1), the resultant complex dissociating very slowly (kdissoc ≈ 3 × 10-7 s-1) in CDCl3 at 60 °C. During the course of these studies, the binding selectivity of a ruthenium porphyrin monomer, Ru(CO)3, for pyridine over THF is estimated to be ca. 7 × 104:1.