Ruthenium Bis(terpyridine) Complexes Based on D-P-A Functionalization: Experimental and Theoretical Evidences

Abstract

We have synthesized heteroleptic complexes 1–4 with improved photophysical properties efficient for interfacial charge injection to semiconducting TiO2nanoparticle. The complexes show improved optical properties with τavg varying from 7.18 ns to 3.89 ns, which is greater than 0.25 ns for [Ru(tpy)2](PF6)2 and sufficient to perform the interfacial electron transfer study with semiconducting TiO2. The time‐correlated single photon counting (TCSPC) measurement with colloidal TiO2show quenched decay pattern and decreased lifetime. The electrochemical study exhibit the oxidation potential (Eox ) in the range of 1.11‐1.17 V vs Ag/AgCl reference electrode and found to be shifted cathodically compared to 1.32 V for [Ru(tpy)2](PF6)2. This cathodic shift is due to the presence of electron donating group that make the metal centre more prone to oxidation and the related excited state oxidation potential show stronger reductant behavior in MLCT excited state. Also, the transient absorption studies with TiO2 nanoparticle is in good harmony with photoinduced electron injection from LUMO of complexes to the conduction band (CB) of TiO2 as LUMO level of complexes were above the CB of TiO2(‐3.65 eV). Further, the theoretical (TDDFT) data is in good agreement with experimental data.

Ruthenium (II) Complexes Bearing Heteroleptic Terpyridine Ligands: Synthesis, Photophysics and Solar Energy Conversion

“…The emission spectrum closely followed the absorption bands in the visible region, with the most red‐shifted emission occurring at 670 nm in [ S4 ] (Figure 4, Table 1). As observed in related heteroleptic complexes, [5b,14] , the excited state decay followed a bi‐exponential profile.…”

“…Further, we evaluate the photosensitizing ability of these complexes in a dye‐sensitized solar cell set‐up (DSSC). Out of these four complexes, [ S2 ] was known before [5b] . However, we present an improved synthetic route with a detailed investigation of its electronic structure and solar cell characteristics.…”

Terpyridine Based Heteroleptic Ruthenium Complexes: Influence of Donor and Acceptor Ligands in Photosensitization

“…Further, the directly linked central pyridine and carboxylate anchor in the coordinated tpy 4′‐COOH ligands stabilized the 3 MLCT states of [ S1 ] ‐ [ S3 ]. This stabilization rendered a 13–20 nm redshift to the emissions bands compared to [ S1 ]′ and [ S3 ]′ [2c,11] . Moreover, the order of Δ ‐SCF (T 1 –S 0 ) energies corroborates the experimental emission peaks (Table 1, Figure 2(b)).…”

“…Complexes exhibit longer lifetimes in the absence of phenyl substituent at the anchoring end [12] . [ S1 ]–[ S3 ] display a longer excited state lifetime than [ S1 ]′–[ S3 ]′ bearing phenyl substituents at the acceptor end [2c,11] . Further, the observed lifetime in the order of [ S1 ]>[ S2 ]>[ S3 ] falls in the same order of 3 MLCT and 3 MC energy gap [9] (Table S7, Supporting Information).…”