We report the experimental observation of intrinsic dynamically localized vibrational states in crystals of the highly nonlinear halide-bridged mixed-valence transition metal complex ͕͓Pt͑en͒ 2 ͔ ͓Pt͑en͒ 2 Cl 2 ͔ ͑ClO 4 ͒ 4 ͖, where en ethylenediamine. These states are identified by the distinctive structure and strong redshifts they impose upon the overtone resonance Raman spectra. Quantitative modeling of the observed redshifts is presented based on a nonadiabatic coupled electron-lattice model that self-consistently predicts strong nonlinearity and highly localized multiquanta bound states.[S0031-9007(99)08915-2]

Pt(( n Bu) 3 P) 2 (ethynylbenzene) 2 ] and [Pt(( n Bu) 3 P) 2 (1,4-diethynylbenzene) 2 ], which possess D 2h micro-symmetry in their ground states, were studied at 77 K by time-resolved infrared (TRIR), FTIR, steady-state emission, and time-resolved photoluminescence spectroscopies. The primary luminescence peaks are at 22 573 cm -1 and 20 408 cm -1 , respectively, with additional resolved structure from both phenyl ring and ethynyl vibrations. A quantum chemical modeling study showed that the HOMO is composed of conjugated π-obitials, which include contribution from the d xy orbital on the platinum metal, while the LUMO consists of only the ligand π* antibonding orbitals, thus the excitation is a mixture of ππ* and MLCT. From the results of the TRIR study and from group theoretical requirements, it has been concluded that the excitation in the lowest triplet manifold is confined to one ligand, resulting in a reduction of symmetry to C 2V . For the ethynylbenzene compound, the lowest energy grow-in in the TRIR spectrum is in the range of a stretching vibration for a carbon-carbon double bond. In the 1,4-diethynylbenzene compound, the low-energy grow-in in the TRIR spectrum is intermediate between a doubly and triply bound carbon stretch. An explanation of the localization is presented through a coupling of the lowest energy 3 B 3u electronic manifold to a B 3u anti-symmetric ethynyl stretch on the peripheral ligands.

We have directly time resolved the lattice motions associated with the formation of the self-trapped exciton in the quasi-one-dimensional system [Pt(en)(2)] [Pt(en)2Br2];(PF6)(4) ( en = ethylene-diamine, C2H8N2), using femtosecond impulsive excitation techniques. A strongly damped, low-frequency wave packet modulation at approximately 110 cm(-1) accompanies the formation of the self-trapped exciton on a approximately 200 fs time scale following excitation of the intervalence charge-transfer transition. Coherent oscillations at the ground state vibrational frequency and its harmonics are also detected.

Cytochrome P450 reductase (CPR) is the redox partner for most human cytochrome P450 enzymes. It is also believed that CPR is an integral membrane protein exclusively. Herein, we report that, contrary to this belief, CPR can exist as a peripheral membrane protein in the absence of NADPH and will transition to an integral membrane protein in the presence of stoichiometric amounts of NADPH or greater. All experiments were performed in a solid-supported cushioned lipid bilayer that closely matched the chemical composition of the human endoplasmic reticulum and served as an ER biomimetic. The phase characteristics and fluidity of the ER biomimetic was characterized with fluorescence micrographs and temperature-dependent fluorescence recovery after photobleaching. The interactions of CPR with the ER biomimetic were directly observed by tracking single CPR molecules using time-lapse single-molecule fluorescence imaging and subsequent analysis of tracks. These studies revealed dramatic changes in diffusion coefficient and the degree of partitioning of CPR as a function of NADPH concentration.

In order to quantify the effect of metal d-orbitals on the radiative properties of the triplet spin sublevels of the ligand-localized 3aa* state, we have studied the phosphorescence from the ligand-localized 3aa* state of cisRh(CN)z(phen)zCl and Rh(phen)3Cl3 in the crystalline state at 1.3 K by optical detection of magnetic resonance (ODMR). The ODMR experiments show that only the T,-spin sublevel is emissive for cis-Rh(CN)z(phen)zCl, whereas the T, and T, sublevels are both emissive for Rh(phen)3Cl3. These experimental results are satisfactorily interpreted in terms of the modulation of the configurational mixing of singlet and triplet da* and dd states with the phen-localized aa* and UT* states induced by changes in ligand-field strength.