Synthesis and Photophysical Properties of Zeolite-Entrapped Bisterpyridine Ruthenium(II). Dramatic Consequences of Ligand-Field-State Destabilization

Abstract

A bisterpyridine complex of ruthenium(II) (Ru(tpy)2 2+) has been prepared in zeolite Y supercages and investigated by electronic absorption, electronic emission, and resonance Raman spectroscopy. In free solution this complex is practically nonluminescent, having a very short excited-state lifetime (250 ps) at room temperature. However, entrapment within the zeolite supercage results in dramatic increases in emission intensity and excited-state lifetime (140 ns) at room temperature. The observed temperature dependence of the excited-state lifetime has been modeled by a kinetic equation with two thermal terms corresponding to the so-called fourth 3MLCT state and ligand-field state (LF), respectively. It is shown that the increased lifetime of the entrapped complex results from zeolite-induced destabilization of the LF state, a conclusion which is in agreement with results obtained for a number of other zeolite-entrapped ruthenium(II) polypyridine complexes.

Resonance Raman Studies of Bis(terpyridine)ruthenium(II) Amino Acid Esters and Diesters

“…All rR spectra reveal sets of modes characteristic for the coordinated terpyridine ligands which is evident when comparing with the rR data of the unsubstituted complex [Ru(tpy) 2 ]-(PF 6 ) 2 ( Figure 3, Table 2). [13,34] Common to all ester complexes 1a-1c is the resonance enhancement of a 1726 cm -1 mode which is easily assigned to the carbonyl stretching vibration of the ester groups ( Figure 3). [18] In the off-resonance Raman spectrum of the tpy-COOC 2 H 5 ligand in the solid state this vibration is observed at 1721 cm -1 (Supporting Information).…”

“…[12] One possibility to enhance the excited state properties of [Ru(tpy) 2 ] 2+ complexes is to entrap the complex in porous matrices (e.g. zeolites [13] ) while a different approach is based on substitution of the terpyridine ligands on the 4Ј positions with electron-donating or -withdrawing groups. [11,14,15,16,17] For example, [Ru(tpy)(tpy-COOC 2 H 5 )] 2+ emits at λ max = 667 nm with a quantum yield of φ = 2.7 ϫ 10 -4 and τ = 32 ns at 298 K in acetonitrile.…”

The Development of Zeolite-Entrapped Organized Molecular Assemblies

“…[17] This complex has an extremely short 3 MLCT state lifetime of 250 ps in aqueous solution at room temperature, the rapid decay being most reasonably attributed to a very low-lying LF state. [19] The corresponding zeolite-entrapped complex Z-[Ru(tpy) 2 ] 2 , emits very strongly at room temperature and exhibits a 3 MLCT state lifetime of over 100 ns, an increase by a factor of almost 1000.…”

Electronic Conduction in Photoactive Metallo‐wires

“…This situation has been considered in detail for Ru-terpy [196]. A viable strategy for prolonging the triplet lifetime, therefore, involves raising the energy of the MC state, either by substitution [197] or by incorporating the compound in a zeolite framework [198]. The opposite approach of lowering the triplet energy of the metal complex has worked very well for Ru-terpy derivatives [199] and, by attaching ethynylene groups at the 4 0 -position (Fig.…”