Resonance Raman Investigation of the MLCT Transition in [Pt(dppm)₂(PhC⋮C)₂] and the MMLCT Transition in [Pt₂(μ-dppm)₂(μ-PhC⋮C)(PhC⋮C)₂]⁺

Abstract

We report resonance Raman spectra including absolute Raman cross section measurements obtained with excitation wavelengths within the MLCT absorption band of [Pt(dppm) 2 (PhCtC) 2 ] and the MMLCT absorption band of [Pt 2 (µ-dppm) 2 (µ-PhCtC)(PhCtC) 2 ] + . We have simultaneously simulated the absolute absorption and resonance Raman intensities in order to estimate the vibrational reorganizational energies associated with the MLCT and MMLCT transitions. We observe a small amount of fluorescence background underneath the resonance Raman spectra of [Pt(dppm) 2 (PhCtC) 2 ] which we attribute to emission from the very shortlived initially excited MLCT state. Our quantum yield measurements of this fluorescence yields an excited state lifetime of approximately 80-130 fs.

Room‐Temperature Phosphorescence and Energy Transfer in Luminescent Multinuclear Platinum(II) Complexes of Branched Alkynyls

“…Table 2 summarizes the photophysical data of the complexes. With reference to previous spectroscopic works on trans ‐[Pt(PEt 3 ) 2 (CCR) 2 ],37–41 in which the absorption bands at approximately 300–360 nm were assigned as metal‐to‐alkynyl metal‐to‐ligand charge transfer (MLCT) transitions, it is likely that the low‐energy transitions in these branched complexes would also involve a certain degree of MLCT character. Another piece of evidence for a MLCT assignment of the low‐energy absorption bands in these complexes was provided by the resonance Raman investigation of trans ‐[Pt(PEt 3 ) 2 (CCH) 2 ] and trans ‐[Pt(dppm) 2 (CCPh) 2 ] (dppm=1,2‐bis(diphenylphosphino)methane) 38.…”

“…Another piece of evidence for a MLCT assignment of the low‐energy absorption bands in these complexes was provided by the resonance Raman investigation of trans ‐[Pt(PEt 3 ) 2 (CCH) 2 ] and trans ‐[Pt(dppm) 2 (CCPh) 2 ] (dppm=1,2‐bis(diphenylphosphino)methane) 38. 41 It was demonstrated that the initial excited‐state vibrational reorganizational energy and displacement were mostly along the nominal CC stretch; this is in line with an assignment of the absorption band to a MLCT (Pt→CCR) transition 37–41. In addition, the lengthening of the CC bond in the initial 1 MLCT excited states of the mononuclear complexes relative to their ground states was found to be consistent with an expected nominal bond‐order change from 3 to 2.5 for a Pt→π*(CCR) metal‐to‐ligand charge transfer 37–41.…”

“…41 It was demonstrated that the initial excited‐state vibrational reorganizational energy and displacement were mostly along the nominal CC stretch; this is in line with an assignment of the absorption band to a MLCT (Pt→CCR) transition 37–41. In addition, the lengthening of the CC bond in the initial 1 MLCT excited states of the mononuclear complexes relative to their ground states was found to be consistent with an expected nominal bond‐order change from 3 to 2.5 for a Pt→π*(CCR) metal‐to‐ligand charge transfer 37–41. However, the very slight to almost no influence on the absorption energies of the branched complexes 3 – 8 that is exerted by the peripheral aryl‐alkynyl ligands would suggest that the absorption pattern is dominated by intraligand (π→π*(CCR)) transitions.…”

Excited State Dynamics of Isocyano Rhenium(I) Phenanthroline Complexes from Time‐Resolved Spectroscopy

“…The resonance Raman (RR) instrument used for the experiments were similar to the one described elsewhere and the set up will be briefly described here. Light of the second (532 nm), third (355 nm) and fourth (266 nm) harmonics of a Nd:YAG laser (Spectra‐Physics LAB‐170‐10) were passed through a hydrogen Raman shifter to produce the excitation beam for resonance Raman experiments, with power around 0.1–1.5 mJ per pulse.…”

Luminescence Properties and Application of Versatile Coordination Compounds Based on Modified Platinum(II) Terpyridyl Complexes

“…[1] Subsequently, G.Maguns' group reported the preparation and characterization of [Pt(NH 3 ) 4 ][PtCl 4 ] in 1828, so-called Magnus' salt. [2] Since then, great progress has been made in the extensive application of Platinum(II) complexes, [3][4][5][6][7] especially the Platinum(II) terpyridyl complexes. The reason can be attributed to their useful physical and biological properties, [8][9] as well as interesting luminescence behaviors [10][11] .…”