Quaterpyridine Ligands for Panchromatic Ru(II) Dye Sensitizers

摘要

A new general synthetic access to carboxylated quaterpyridines (qpy), of interest as ligands for panchromatic dyesensitizednsolar cell organometallic sensitizers, is presented. The strategic step is a Suzuki−Miyaura cross-coupling reaction,nwhich has allowed the preparation of a number of representative unsubstituted and alkyl and (hetero)aromatic substituted qpys.nTo bypass the poor inherent stability of 2-pyridylboronic acid derivatives, we successfully applied N-methyliminodiacetic acidn(MIDA) boronates as key reagents, obtaining the qpy ligands in good yields up to (quasi)gram quantities. The structural,nspectroscopic (NMR and UV−vis), electrochemical, and electronic characteristics of the qpy have been experimentally andncomputationally (DFT) investigated. The easy access to the bis-thiocyanato Ru(II) complex of the parent species of the qpynseries, through an efficient route which bypasses the use of Sephadex column chromatography, is shown. The bis-thiocyanatonRu(II) complex has been spectroscopically (NMR and UV−vis), electrochemically, and computationally investigated, relating itsnproperties to those of previously reported Ru(II)−qpy complexes.