Charge intra-ligand

QPVP is a positively charged polymer ligand. When Cu(II) ion was added to the QPVP solution, the viscosity of the solution fell to one eighth that of the free QPVP ligand [tj /c = 6.23 dl/g for QPVP, 0.84 for QPVP-Cu(II)]160>. This indicates that the QPVP chain is contracted into a compact structure due to intra-polymer... 

Three types of electronic transition can be distinguished among compounds of the d block transition elements d-d bands, charge transfer (or electron-transfer) bands and intra-ligand bands. Configuration interaction may make the distinctions rather hazy, however. 

These are electronic transitions between orbitals that are largely localised on different atoms. In coordination compounds ML where M is a d block element and L represents the ligands, we can distinguish two types of charge transfer L —> M and M — L. These are depicted schematically in Fig. 2.2, along with d-d transitions and intra-ligand transitions. 

Hpba Hppbpy Hppy Hpq HSA IgG IL LLCT mcsubpy 4-(2-Pyridyl)benzaldehyde 4-(4-Hydroxyphenyl)-6-phenyl-2,2 -bipyridine 2-Phenylpyridine 2-Phenylquinoline Human serum albumin Immunoglobulin G Intra-ligand Ligand-to-ligand charge transfer 4-Carboxy-4 -methyl-2,2 -bipyridine N-hydroxysuc- cinimide ester... 

Shavaleev, N.M., Scopelliti, R., Gumy, R, andBunzli, J.C.G. (2008) Visible-light excitation of infrared lanthanide luminescence via intra-ligand charge-transfer state in 1,3-diketonates containing push-pull chromophores. European Journal of Inorganic Chemistry, (9), 1523-1529. 

LC ligand centered MLCT metal-to-ligand charge transfer ILCT intra-ligand charge transfer. 

The four processes are intra-ligand transitions, ligand-to-metal charge transfer, metal-to-ligand charge transfer and d- d transitions. Refer to Section 7.2.1 for the explanation of these terms. 

Del Guerzo, A. Leroy, S. Fages, F. Schmehl, R. H. Photophysics of Re(I) and Ru(II) diimine complexes covalently linked to pyrene contributions from intra-ligand charge transfer states. Inorg. Chem. 2002, 41, 359-366. 

Many other copper (II) complexes with unsaturated chelating ligands are of great interest, such as copper phthalocyanin, but little is known about the d—d spectra of such molecules intra-ligand bands, as well as charge transfer bands in some cases, are so intense as to mask the d—d absorption. 

Here, the dipole operator r is divided into two contributions r(A/) and r(L) which operate only within the Mg and Eg states, respectively, excluding the possibility of charge transfer effect. Focusing on the matrix elements of dipole operators in Eq. (6), the first and second terms, which contain (Ma r(M) Mc ) and Mg r M) Mb), express intrametal excitations derived from the JO theory and the third and fourth terms, which contain (Lg r(L) Le ) and (Le r(L) Lg), express intra-ligand excitations derived from the DC model. When the Coulombic potential between nonoverlapping transition charge distributions of Mb and... 

P Puyiir), and r P r) represent the values of the sum of the matrix elements of the transition dipole moment within Ln, those between Ln and X, and those within X, respectively. We have previously decomposed TDM based on the AO centers and shown the results in Table 2 and Fig. 2 of Ref. [5]. From that work, it is clear that the three areas above mainly represent the sum of matrix elements of the transition dipole moment between 4f and intra-Ln excitation CSFs, those between 4f and ligand-to-metal charge transfer (LMCT) excitation CSFs, and those between 4f and intra-ligand excitation CSFs, respectively. In other words, the areas of r PuJj) and r Pxxir) represent the effects of the JO theory and the DC model, respectively. 

An interesting series of complexes to study intra-ligand coupling mediated by the metal ion would be species of the general class [M(LL)X4(R-L)]"" where the M LL charge transfer band could be monitored as a function of R-L. Such series are very rare (e.g., [Re(bpy)(CO)3(R-Py)]" ). As anticipated, the /ii/(Re 7r bpy) transition is linearly dependent on (Tp(R) (Table 2 ). 

Fig. 7 Schematic representation of energy absorption, migration, emission (plain arrows) and dissipation (dotted arrows) processes in a lanthanide complex. S or S = singlet state, T or T = triplet state, A = absorption, F = fluorescence, P = phosphorescence, k = rate constant, r = radiative, nr = nonradiative, IC = internal conversion, ISC = intersystem crossing, ILCT (or IL) = intra-ligand charge transfer, LMCT (or LM) = ligand-to-metal charge transfer. Back transfer processes are not drawn for the sake of clarity...

An alternative route to long-lived excited states in transition metal complexes is to populate an excited state localised on a pendant arm. For example, a switch from a very short lived MLCT state in [Pt(tpy)Cl] to a long-lived intra-pyrene excited state in [(4 -pyrene)-tpy-Pt-Cl] , has been demonstrated an electron-rich aryl substituent at the 4 position of the tpy ligand promotes the low-lying excited state with intra-ligand charge-transfer (ILCT) character, enhances the emission intensity, and extends the excited-state lifetime up to 64 ps in r.t. dichloromethane solution [35]. 

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