TY - JOUR
T1 - Optical Properties of the Atomically Precise C4Core [Au9(PPh3)8]3+Cluster Probed by Transient Absorption Spectroscopy and Time-Dependent Density Functional Theory
AU - Madridejos, Jenica Marie L.
AU - Harada, Takaaki
AU - Falcinella, Alexander J.
AU - Small, Thomas D.
AU - Golovko, Vladimir B.
AU - Andersson, Gunther G.
AU - Metha, Gregory F.
AU - Kee, Tak W.
PY - 2021/1/28
Y1 - 2021/1/28
N2 - Structural isomerism of [Au9(PPh3)8]3+ has been studied experimentally, mostly concerning the symmetry of the Au9 core. Recently, the C4 isomer of [Au9(PPh3)8]3+ has been shown to exist in solution phase while the D2h isomer is present in the solid state [Inorg. Chem. 2017, 56, 8319-8325]. In this work, geometric, electronic, and optical properties of C4 [Au9(PPh3)8]3+ are investigated by using the combined second-order density-functional tight-binding (DFTB2) method and time-dependent density functional theory (TD-DFT) calculations with spin-orbit coupling. Additionally, the excited-state relaxation dynamics of the [Au9(PPh3)8]3+ cluster in dichloromethane and methanol solutions are studied using femtosecond transient absorption spectroscopy. [Au9(PPh3)8]3+ is optically pumped to different excited states by using 432, 532, and 603 nm light. For all three pump wavelengths, the photoexcitation event induces an excited-state absorption (ESA) band centered at 600 nm with decay time constants of 2.0 and 45 ps, which are attributed to intersystem crossing and nonradiative relaxation of [Au9(PPh3)8]3+, respectively. On the other hand, optical pumping of [Au9(PPh3)8]3+ using 432 nm light gives rise to an additional ESA band at 900 nm. This band exhibits fast relaxation through internal conversion with a time constant of ∼0.3 ps. Our combined computational and experimental study reveals that the excitation wavelength-dependent relaxation dynamics of the [Au9(PPh3)8]3+ cluster are related to the different electron densities of the excited states of [Au9(PPh3)8]3+, consistent with it possessing molecular-like electronic states.
AB - Structural isomerism of [Au9(PPh3)8]3+ has been studied experimentally, mostly concerning the symmetry of the Au9 core. Recently, the C4 isomer of [Au9(PPh3)8]3+ has been shown to exist in solution phase while the D2h isomer is present in the solid state [Inorg. Chem. 2017, 56, 8319-8325]. In this work, geometric, electronic, and optical properties of C4 [Au9(PPh3)8]3+ are investigated by using the combined second-order density-functional tight-binding (DFTB2) method and time-dependent density functional theory (TD-DFT) calculations with spin-orbit coupling. Additionally, the excited-state relaxation dynamics of the [Au9(PPh3)8]3+ cluster in dichloromethane and methanol solutions are studied using femtosecond transient absorption spectroscopy. [Au9(PPh3)8]3+ is optically pumped to different excited states by using 432, 532, and 603 nm light. For all three pump wavelengths, the photoexcitation event induces an excited-state absorption (ESA) band centered at 600 nm with decay time constants of 2.0 and 45 ps, which are attributed to intersystem crossing and nonradiative relaxation of [Au9(PPh3)8]3+, respectively. On the other hand, optical pumping of [Au9(PPh3)8]3+ using 432 nm light gives rise to an additional ESA band at 900 nm. This band exhibits fast relaxation through internal conversion with a time constant of ∼0.3 ps. Our combined computational and experimental study reveals that the excitation wavelength-dependent relaxation dynamics of the [Au9(PPh3)8]3+ cluster are related to the different electron densities of the excited states of [Au9(PPh3)8]3+, consistent with it possessing molecular-like electronic states.
KW - structural isomerism
KW - transient absorption
KW - spectroscopy
KW - time-dependent density functional theory
KW - isomer
KW - Electron density differences
UR - http://www.scopus.com/inward/record.url?scp=85100033325&partnerID=8YFLogxK
UR - http://purl.org/au-research/grants/ARC/LE0989747
U2 - 10.1021/acs.jpcc.0c08838
DO - 10.1021/acs.jpcc.0c08838
M3 - Article
AN - SCOPUS:85100033325
VL - 125
SP - 2033
EP - 2044
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 3
ER -