Bond shortening (1.4 Å) in the Singlet and Triplet Excited States of [Ir2(dimen)4]2+ in solution Determined by Time-resolved X-ray Scattering

TY - JOUR

T1 - Bond shortening (1.4 Å) in the Singlet and Triplet Excited States of [Ir2(dimen)4]2+ in solution Determined by Time-resolved X-ray Scattering

AU - Haldrup, K.

AU - Harlang, T.

AU - Christensen, Morten

AU - Dohn, A.

AU - van Driel, T. B.

AU - Kjaer, K. S.

AU - Harrit, Niels Holger

AU - Vibenholt, Johan Elias

AU - Guerin, L.

AU - Wulff, M.

AU - Nielsen, M. M.

PY - 2011/10/3

Y1 - 2011/10/3

N2 - Ground- and excited-state structures of the bimetallic, ligand-bridged compound Ir2(dimen)42+ are investigated in acetonitrile by means of time-resolved X-ray scattering. Following excitation by 2 ps laser pulses at 390 nm, analysis of difference scattering patterns obtained at eight different time delays from 250 ps to 300 ns yields a triplet excited-state distance between the two Ir atoms of 2.90(2) Å and a triplet excited-state lifetime of 410(70) ns. A model incorporating the presence of two ground-state structures differing in Ir-Ir separation is demonstrated to fit the obtained data very well, in agreement with previous spectroscopic investigations. Two ground-state isomers with Ir-Ir separations of 3.60(9) and 4.3(1) Å are found to contribute equally to the difference scattering signal at short time delays. Further studies demonstrate the feasibility of increasing the effective time resolution from the ∼100 ps probe width down to the 10 ps regime by positioning the laser pump pulse at selected points in the X-ray probe pulse. This approach is used to investigate the structures of both the singlet and the triplet excited states of Ir2(dimen)42+.

AB - Ground- and excited-state structures of the bimetallic, ligand-bridged compound Ir2(dimen)42+ are investigated in acetonitrile by means of time-resolved X-ray scattering. Following excitation by 2 ps laser pulses at 390 nm, analysis of difference scattering patterns obtained at eight different time delays from 250 ps to 300 ns yields a triplet excited-state distance between the two Ir atoms of 2.90(2) Å and a triplet excited-state lifetime of 410(70) ns. A model incorporating the presence of two ground-state structures differing in Ir-Ir separation is demonstrated to fit the obtained data very well, in agreement with previous spectroscopic investigations. Two ground-state isomers with Ir-Ir separations of 3.60(9) and 4.3(1) Å are found to contribute equally to the difference scattering signal at short time delays. Further studies demonstrate the feasibility of increasing the effective time resolution from the ∼100 ps probe width down to the 10 ps regime by positioning the laser pump pulse at selected points in the X-ray probe pulse. This approach is used to investigate the structures of both the singlet and the triplet excited states of Ir2(dimen)42+.

M3 - Journal article

SN - 0020-1669

VL - 50

SP - 9329

EP - 9336

JO - Inorganic Chemistry

JF - Inorganic Chemistry

ER -