TY - JOUR
T1 - Probing the excited states of d6 metal complexes containing the 2,2′-bipyrimidine ligand using time-resolved infrared spectroscopy. 1. Mononuclear and homodinuclear systems
AU - Alsindi, Wassim Z.
AU - Easun, Timothy L.
AU - Sun, X. Z.
AU - Ronayne, Kate L.
AU - Towrie, Michael
AU - Herrera, Juan Manuel
AU - George, Michael W.
AU - Ward, Michael D.
PY - 2007/4/30
Y1 - 2007/4/30
N2 - This paper reports time-resolved infrared (TRIR) spectroscopic studies on a series of weakly luminescent or nonluminescent 2,2′-bipyrimidine-based complexes to probe their electronic structure and the dynamic behavior of their excited states on the picosecond and nanosecond time scales. The complexes are mononuclear [Re(CO)3Cl-(bpm)] (1), [Ru(CN)4(bpm)] 2- (2), and [Ru(bpyam)2(bpm)]2+ (3) [bpm = 2,2′-bipyrimidine; bpyam = 2,2′-bipyridine-4,4′-(CONEt 2)2] and their homodinuclear analogues [{Re(CO) 3Cl}2(μ-bpm)] (4), [{Ru(CN)4} 2(μ-bpm)]2- (5), and [{Ru(bpyam)2} 2(μ-bpm)]4+ (6). Complex 1 shows the characteristic shift of the three ν(CO) bands to higher energy in the Re → bpm triplet metal-to-ligand charge-transfer (3MLCT) state, which has a lifetime of 1.2 ns. In contrast, the dinuclear complex 4 shows ν(CO) transient bands to both higher and lower energy than the ground state indicative of, on the IR time scale, an asymmetric excited state [(OC)3CIRe I(bpm•-)ReII(CO)3Cl] whose lifetime is 46 ps. The cyanoruthenate complexes 2 and 5 show comparable behavior, with a shift of the ν(CN) bands to higher energy in the excited state for mononuclear 2 but two sets of transient bands - one to higher energy and one to lower energy-in dinuclear 5, consistent with an asymmetric charge distribution [(NC)4RuII(bpm•-)Ru III(CN)4]4- in the 3MLCT state. These cyanoruthenate complexes have much longer lifetimes in D2O compared with CH3CN, viz., 250 ps and 3.4 ns for 2 and 65 ps and 1.2 ns for 5 in CH3CN and D2O, respectively. In complex 3, both higher-energy Ru → bpyam and lower-energy Ru → bpm 3MLCT states are formed following 400 nm excitation; the formr decays rapidly (τ = 6-7 ps) to the latter, and the subsequent decay of the Ru → bpm 3MLCT state occurs with a lifetime of 60 or 97 ns in D2O or CH3CN, respectively. Similar behavior is shown by dinuclear 6 in both D2O and CH3CN, with initial interconversion from the Ru → bpyam to the Ru → ;bpm 3MLCT state occurring with τ ∼ 7 ps and the resultant Ru → bpm 3MLCT state decaying on the nanosecond time scale.
AB - This paper reports time-resolved infrared (TRIR) spectroscopic studies on a series of weakly luminescent or nonluminescent 2,2′-bipyrimidine-based complexes to probe their electronic structure and the dynamic behavior of their excited states on the picosecond and nanosecond time scales. The complexes are mononuclear [Re(CO)3Cl-(bpm)] (1), [Ru(CN)4(bpm)] 2- (2), and [Ru(bpyam)2(bpm)]2+ (3) [bpm = 2,2′-bipyrimidine; bpyam = 2,2′-bipyridine-4,4′-(CONEt 2)2] and their homodinuclear analogues [{Re(CO) 3Cl}2(μ-bpm)] (4), [{Ru(CN)4} 2(μ-bpm)]2- (5), and [{Ru(bpyam)2} 2(μ-bpm)]4+ (6). Complex 1 shows the characteristic shift of the three ν(CO) bands to higher energy in the Re → bpm triplet metal-to-ligand charge-transfer (3MLCT) state, which has a lifetime of 1.2 ns. In contrast, the dinuclear complex 4 shows ν(CO) transient bands to both higher and lower energy than the ground state indicative of, on the IR time scale, an asymmetric excited state [(OC)3CIRe I(bpm•-)ReII(CO)3Cl] whose lifetime is 46 ps. The cyanoruthenate complexes 2 and 5 show comparable behavior, with a shift of the ν(CN) bands to higher energy in the excited state for mononuclear 2 but two sets of transient bands - one to higher energy and one to lower energy-in dinuclear 5, consistent with an asymmetric charge distribution [(NC)4RuII(bpm•-)Ru III(CN)4]4- in the 3MLCT state. These cyanoruthenate complexes have much longer lifetimes in D2O compared with CH3CN, viz., 250 ps and 3.4 ns for 2 and 65 ps and 1.2 ns for 5 in CH3CN and D2O, respectively. In complex 3, both higher-energy Ru → bpyam and lower-energy Ru → bpm 3MLCT states are formed following 400 nm excitation; the formr decays rapidly (τ = 6-7 ps) to the latter, and the subsequent decay of the Ru → bpm 3MLCT state occurs with a lifetime of 60 or 97 ns in D2O or CH3CN, respectively. Similar behavior is shown by dinuclear 6 in both D2O and CH3CN, with initial interconversion from the Ru → bpyam to the Ru → ;bpm 3MLCT state occurring with τ ∼ 7 ps and the resultant Ru → bpm 3MLCT state decaying on the nanosecond time scale.
UR - http://www.scopus.com/inward/record.url?scp=34248353554&partnerID=8YFLogxK
U2 - 10.1021/ic0623112
DO - 10.1021/ic0623112
M3 - Article
C2 - 17391026
AN - SCOPUS:34248353554
SN - 0020-1669
VL - 46
SP - 3696
EP - 3704
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 9
ER -