Time-resolved IR spectroscopy of a trinuclear palladium complex in solution

Abstract

This paper presents a combined spectroscopic and theoretical analysis of a trinuclear [Pd3{Si(mt(Me))3}2] complex (mt(Me) = methimazole) which has been demonstrated to be a potential catalyst for coupling reactions. It is a highly symmetric model system (D3 in the electronic ground state) for the investigation of electronic states and the structure of polynuclear transition metal complexes. Different time-resolved IR spectroscopic methods covering the femtosecond up to the microsecond range as well as density functional computations are performed to unravel the structure and character of this complex in the electronically excited state. These are the first time-resolved IR studies on a trinuclear Pd complex. Based on the interplay between the computational results and those from the IR studies a (3)A state is identified as the lowest lying triplet state which has C2 symmetry.

Spectroscopic, Structural, and Kinetic Investigation of the Ultrafast Spin Crossover in an Unusual Cobalt(II) Semiquinonate Radical Complex

“…The latter,e specially,w ould show as positive transient absorbance strength on the low-energye dge of the observed negative and positive bands,d ue to anharmonic coupling of these modes to thermally populated low frequencyv ibrational modes. This is surprising because IVR and thermalization are expectedt oo ccur on the sub-picosecondt ime scale [49,54,55,57,58] and vibrational cooling is expected to occur in the regime of 1-20 ps. [43,49,54,55,[57][58][59] On the other hand, the excesse nergy of 9000 cm À1 is relatively small compared to UV-excitation (available excesse nergy typically > 25 000 cm À1 )i ns everalr elated experiments, [43,49,[57][58][59] and the number of vibrational degrees of freedom( 3 N-6) of the investigated Co II complex (N = 95) is larger than those of the reported complexes( N 80 [43,[57][58][59] ).…”

Luminescence and Light‐Driven Energy and Electron Transfer from an Exceptionally Long‐Lived Excited State of a Non‐Innocent Chromium(III) Complex

“…[49] Furthermore,t pe could be susceptible to ligand-based redox chemistry (ligand non-innocence) similar to t bpy,tpy or Me PDP 2À , [1,2] contrasting ddpd as aredox-innocent spectator ligand. [6] In this study,wee xploit the complex [Cr(tpe) 2 ] 3+ with an Earth-abundant metal ion as ap otential substitute for the classical, precious metal containing chromophore [Ru-(bpy) 3 ] 2+ in luminescence,a sw ell as in photoinduced energy and electron transfer reactions.S ingle crystal X-ray diffraction, [50][51][52][53][54] NIR luminescence quantum yields [55] and lifetimes, variable temperature luminescence and step-scan FT-IR spectroscopy, [56][57][58] electrochemistry and spectroelectrochemistry,S tern-Volmer analyses as well as quantum chemical calculations [59][60][61][62][63][64][65][66][67][68][69] confirm the proposed design guidelines.…”

“…Thei ncrease in emission intensity is compatible with the proposed diminished k nr (surface) at lower temperature of the "pseudo-Stokes shifted" 2 X g (D 3d ) state (Figure 3). [79] To gain more insight into the geometries of the long-lived excited states,w es ubjected KBr disks of [Cr(tpe) 2 ][BF 4 ] 3 to time-resolved step-scan FTIR spectroscopy [56][57][58]80] in the energy range of 1750 to 1200 cm À1 at 290 and 20 K ( Figure 5a). Thenegative bands in the difference spectra indicate depopulation of the ground state while positive bands belong to the electronically excited state(s).…”

Structural Characterization and Lifetimes of Triple‐Stranded Helical Coinage Metal Complexes: Synthesis, Spectroscopy and Quantum Chemical Calculations

“…Nowadays, large heterometallic complexes still lack thorough spectroscopic investigation, in comparison to the large number of investigations on mononuclear [1,2] and polynuclear homometallic [3,[4][5][6] complexes. Especially, heterometallic transition metal complexes are extremely demanding regarding high-level spectroscopic experiments, which is one reason there are so few examples found in the literature.…”