Charge-transfer absorption band function

The demetalation process was followed by absorption spectrophotometry (measurement of the decay, as a function of time and cyanide concentration, of the di-copper(I) complexes characteristic metal-to-ligand-charge-transfer (MLCT) bands in the visible region [111]) which gave access to the kinetic parameters, in particular to the second-order dissociation rate constants CN given in Table 1. 

These wavefunctions account for the attractive force between A and D leading to the formation of an EDA complex, for its increased polar character and also for the existence of charge-transfer absorption that is often observed when EDA complexes form. Low-lying excited states of A or D+ must be included in the wave function to describe additional charge-transfer bands. These bands appear in addition to the absorption bands of the molecules A and D they are usually broad and of low oscillator strengths because there is little overlap between the HOMO of the donor and the LUMO of the acceptor (Section 4.4, Equation 4.20). Many examples of the formation of EDA complexes between, for example, tetracyanoethylene and aromatic hydrocarbons are known. The... 

The principle of the experiment is as follows a first pump pulse at 400 nm (Pump4oo) excites the electron donor (Pe) into its Si electronic state. After a variable time delay Ati (up to 1 ns) a conventionnal pump-probe measurement is performed at 530 nm (Pumps3o and Probes3o) on the ensuing transient species (Fig. lb). It allows us to determine the GSR dynamics of the Pe + cation upon excitation in its Do - Ds absorption band as a function of time delay after phototriggering the charge transfer reaction, i.e. as a function of the age of the transient. 

Figure 3.49 Examples of solvatochromic plots of absorption spectra, (a) The first absorption band of 4-nitroaniline (charge transfer band), (b) The first absorption band of acetone (n-n band). The ordinates are in units of 103 cm, measured at the band maximum the abcissa are in units of Onsager solvent polarity function f(D)...

Optical Spectra. The main (a) band in a variety of visual pigments exhibits absorption maxima in the range between 430 and 580 nm. It is this variability, as well as the basic bathochromic shift relative to a free PRSB in solution, which have provided the basis for most of the spectroscopic theories relevant to the structure of the chromophore and its environment in the binding site. Attempts to rationalize the shift in terms of charge-transfer complex formation between the (unprotonated) Schiff base and a protein functional group (200,210,212,228) have never... 

Another charge-transfer phenomenon has been observed for the series [Cr(bipy)2Cl2]X MH20 (29), and for [Ir(phen)3]X3 wH20 (156). The color of the complex is a function of X. As the reducing power of X increases, the absorption band undergoes a red shift. The phenomenon is attributed to a redox process of the variety M(III)X <- M(II)X. 

---