Intraligand-charge transfer

Both states are thought to arise from an intraligand charge-transfer (TLCT) transition with considerable 1,2-enedithiolate n to heterocycle n character (17-19, 22, 31). This transition is generally in the 400-500 nm (25,000-20,000 cm-1) range and is the lowest lying band in the emissive heterocyclic-substituted platinum 1,2-enedithiolates. 

These complexes display an intense absorption at 400-550 nm due to intraligand charge-transfer absorption, which allows visible-light excitation of NIR-emitting Nd(III), Er(III), and Yb(III) ions with excitation wavelengths up to 550 nm. 

Yersin, H. Donges, D. Nagle, J. K. Sitters, R. Glasbeek, M. Intraligand charge transfer in the Pd(II) oxinate complex Pd(qol)(2). Site-selective emission, excitation, and optically detected magnetic resonance. Inorg. Chem. 2000, 39, 770-777. 

However, when the Schiff base ligand is substituted by donor and acceptor substituents such in 61 (A = NO2), the situation is different and the jd response is now dominated by intraligand charge transfer transitions, with the metal ion mainly acting as a bridging centre (Figure 1.26). ... 

It is also possible that coordination of a metal alters the electron affinity of a portion of the ligand, resulting in observation of absorption and emission from a eharge transfer state localized on the ligand (intraligand charge transfer, ILCT). ... 

Several reports have taken advantage of this unique property to design a variety of photoswitching systems in recent years.Moore and co-workers reported one particularly interesting example. The complexes in their study are yhc-Re(CO)3(bpy) chromophores linked by a styryl pyridine that attaches an amine or an azacrown ether group (see Scheme 4 for structures). The absorption spectra of these complexes feature an intense intraligand charge-transfer (ILCT) band, which can be removed by protonation of the amine or azacrown... 

CT Computed Tomographic ILCT Intraligand Charge Transfer... 

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