Chromophores energy level diagram

Figure 1.2. Jablonski energy level diagram showing the singlet state and the triplet state with its zero-field splittings for a planar aromatic chromophore.

Fig. 17. Energy level diagram for the vanadium(III) ion (d ) in a five-coordinate chromophore of Dan symmetry. The diagram is valid for the ratios DsjDt= 1/3 and CjB — A.S. The dotted lines indicate the DtjB ratio found for VCls(NMe3)2. [(By permission of J. Chem. Soc. (Ref. (14))]...

Fig. 20. Energy level diagrams for square pyramidal chromophores of cobalt(II). Left, Dq(ax) =Dg (base) a= 100°. Middle, the effect of the variation of the ratio Dj(ax)/D (base) for Dq hase) = 1 kK. Right, the effect of the variation of a angle on the energy levels Dq(ax) = X)j(base) = 1 kK...

Energy level diagrams for chromophores with C4v symmetry are shown in Fig. 24. 

Fig. 30. Energy level diagrams for trigonal bipyramidal chromophores of iron(II)...

Fig. 34. Energy level diagram of a electronic configuration in a square pyramidal chromophore (C4v). The state is fixed as the zero of energy. All energies are expressed in units of kilokaysers. Dq — 3.3 B = 0.75 Ds= 1.5 Dt CjB = 4.633. (By permission of Inorg. Chem. (Ref. (7/))...

Figure 4 Energy level diagram for an octahedral NiA6 chromophore. Full lines refer to triplet states, broken lines to singlet states. The free ion parentage is shown on the left side, (a) The effect of varying ea (e = 0 cm-1) (b) the effect of varying e jea ea = 3000 cm-1) (c) the effect of varying g (see text e = 3000 cm-1, e = 0 cm-1)...

Scheme 1 Energy level diagram and reaction rates for the photoinduced processes occurring in triad 24+ at 155 K. Excitation (dashed arrow) on the DPAA chromophore...

Fig. 32 Typical energy level diagram illustrating the photophysical processes that take place upon local excitation of the donor chromophore (a similar scheme obtains for excitation of the acceptor chromophore). kd represents both radiative (fluorescence) and non-radiative decay processes.

Fig. 3. Jablonski energy-level diagram typical for chromophores involved in ONP processes (specifically for pentacene in naphthalene, after Ref. [39]), showing the respective roles of optical excitation, ISC, OEP, electron-nuclear polarization transfer (here driven by mw radiation), and subsequent decay to the diamagnetic ground state. The relative populations of the triplet magnetic sublevels are given at the far right (assuming the crystal is oriented such that the long molecular axis of pentacene is parallel to the external magnetic field ).

Figure 3.31. An energy-level diagram for an aromatic molecule or similar chromophore that may absorb radiation in the visible or UV region of the electromagnetic spectrum (George, 1989).

The molecular box 14 contains two types of chromophores, zinc-porphyrin and free-base porphyrin. The behaviors of the monomeric models of these units, Zn and Fb, have been summarized in Sect. 4.1. As expected for supramolecular species, the absorption spectrum of the box is a good superposition of those of the molecular components (Fig. 22). The energy level diagram for the molecular box, obtained as a combination of those of the Fb and Zn models (Fig. 23), shows a significant driving force for energy transfer from the Zn-porphyrin to the free base units. 

Experimentally, this imphes that selective excitation of the two types of chromophores is feasible (e.g., 100% FBI at 585 mn, 62% Ru(TPP)(CO) at 530 nm). The energy level diagram of 16 (Fig. 35) can be considered as a simple superposition of those of the separated constituents, with the addition of a charge transfer state in which PBI is reduced and the Ru porphyrin is oxidized (energy estimated from electrochemistry). 

Os-chromophores opens up in competition with singlet-triplet intersystem crossing in the Ru-unit. This scenario is illustrated by the energy level diagram in Figure 17. Details of this work can be found in... 

Ru(bpy)2 - chromophoric component) the following observations are made (i) the MLCT emission characteristic of the chromophoric unit is completely quenched (ii) the MC phosphorescence characteristic of the Cr(cyclam)(CN)2 luminophoric units is obtained with high efficiency. This demonstrates the occurrence of very efficient chromophore -> luminophore energy transfer. The behavior of the chromophore-luminophore complex is schematized on the energy level diagram of Fig. 16 [72]. 

In practice, the absorption spectrum of a molecule containing such light-absorbing groups, or chromophores, is not as simple as the energy level diagram in Figure 3.4.1.13 would indicate. The spectrum is compUcated by the fact that transitions of the valence electrons are not simply between occupied and unoccupied electronic states. When vibrational and rotational transitions are taken into account, the absorption spectrum becomes essentially a continuum. 

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