Ligand-to-Metal Charge-Transfer LMCT Absorption Bands

Ligand-to-Metal Charge-Transfer (LMCT) Absorption Bands 257... 

The electronic absorption spectrum of Ti(norbomyl)4 (10) is shown in Fig. 1. The intense band at 245 nm ( = 29,200 moP cm" in hexane) was assigned to a fully allowed ligand-to-metal charge-transfer (LMCT) transition (18). The weaker band at 367 nm (e = 253 mol cm in hexane) and shoulders at 312 and 412 nm were attributed to other spin or orbitally forbidden LMCT transitions. Near-UV irradiation of yellow hexane solu-... 

For Cu+ (d °) and open-shell metal ions, the absorption spectra in the visible spectral range are totally different, and weak bands (e of the order of 10 M cm ) are found up to 600-700 nm. Cu.5+ exhibits the expected wide MLCT absorption (see above), whereas the bands observed for Ni-+ (d ) and Co + (d ) are assigned to metal-centered (MC) or ligand-to-metal-charge-transfer (LMCT) transitions. Finally, the Pd + (d ) catenate has to be considered a special case since it is actually a... 

Fig. 3(A) shows the UV-Vis spectra of 0.1SnO2-MSM samples before and after calcination synthesized with varied periods of HT in comparison to that of commercial SnOa. Two absorption bands with maximum intensities at 220 and 270 nm were observed for the commercial SnOa. The former was assigned to the ligand to metal charge transfer (LMCT) transition from O to Sn, which was at octahedral (Oh) site. The latter band was the electron transition from the valance to conduction bands (band gap ca. 3.76 eV for bulk SnOa) [1]. Only one broad band of very weak intensity was observed in the spectra of the O.lSnOa-MSM samples before calcination, while two bands at 215 and 253 nm were seen for the samples after calcination. The broad band at ca. 205 210 nm for the uncalcined samples was assigned to the LMCT band of 0 to tetrahedral (Td) Sn ions in the silica lattice [17]. When the HT period was prolonged to 24 h, a shoulder appeared ca. 250 nm. These results imply that the Sn02 nanoparticles were probably formed after the HT treatment for 24 h.

The metal-peptide stoichiometry of the dimeric Cd peptide was studied by UV-Vis spectroscopy (77) as an absorption band at 238 nm is observed upon addition of Cd(II) to the peptide which is assigned to the ligand-to-metal charge-transfer (LMCT) transition of the newly formed Cd-S bonds. A Job plot demonstrated that the complex consists of 2 peptides and 1 metal ion. These results were supported by spectrophotometric titrations analyzed according to the following equilibrium (1) to yield n = 2 and IQ = 0.65 0.08 pM. 

The electronic absorption spectra of several complexes containing a [Mn (0)2Mn ] core were investigated in detail using MCD spectroscopy in conjuction with resonance Raman and absorption spectroscopies. The MCD spectra of the Mn-oxo complexes were recorded at 300-2,500 nm, deconvoluted, and the component peaks assigned. The majority of peaks corresponded to metal-centered d-d transitions and oxo-to-Mir ligand-to-metal charge transfer (LMCT) bands. Although contributions from the other chromophores in PSII and low protein... 

Primary Processes. The most common primary photochemical processes Involving copper(II) complexes are ligand to metal charge transfer (LMCT) reactions (6,7), also referred to as charge transfer to metal (CTTM) reactions. LMCT reactions occur when light absorbed In an LMCT absorption band of the Cu(II) complex leads to reduction of the metal and oxidation of the ligand. 

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