Photochemistry of coordination compounds

Sýkora, Ján; Šíma, Jozef

doi:10.1016/0010-8545(90)80055-x

Cited by 108 publications

(47 citation statements)

References 539 publications

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“…Unfortunately, the majority of metal complexes is not emissive. Those complexes which are luminescent [2][3][4][5][6]74,75] are mostly diamagnetic in the ground state. Generally, the emission originates from the energetically lowest triplet state.…”

Section: Emission From Charge Transfer Statesmentioning

confidence: 99%

“…In rare cases a fluorescence originating from the lowest-energy singlet is also observed. Irrespective of the spin multiplicity the luminescence of metal complexes may occur from all types of excited states including IL and MC states [2][3][4][5][6]74,75]. The emitting CT states are classified according to the labels which refer to the transitions in absorption.…”

Section: Emission From Charge Transfer Statesmentioning

confidence: 99%

“…The formation of solvated electrons is thus a typical reaction of MLCT states. In some cases this reaction seems to be induced by CTTS (charge transfer to solvent) excitation [6,37,38,121]. However, CTTS absorptions are often difficult to identify and to distinguish from other bands.…”

Section: Formation Of Solvated Electrons/reduction Of the Solventmentioning

confidence: 99%

“…They are stable in low-temperature matrices but appear only as transients in most solvents at room temperature. Since this subject has been extensively covered in several reviews [6,37,38,121] only a few examples are mentioned here. A variety of reducing cyano complexes are known to photogenerate solvated electrons [122][123][124], e.g., reaction 28:…”

Section: Formation Of Solvated Electrons/reduction Of the Solventmentioning

confidence: 99%

“…Ligand field (LF) or dd excited states have been investigated in great detail [2][3][4][5][6]. In many cases LF (or dd) excitation leads to a weakening of metal-ligand bonds.…”

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confidence: 99%

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Charge Transfer Excitation of Coordination Compounds. Generation of Reactive Intermediates

Vogler

Kunkely

1993

Catalysis by Metal Complexes

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Reactive compounds exhibit frequently catalytic properties. Particularly, many reactive metal complexes are characterized by their catalytic activity. Photochemistry presents one of the most important and versatile methods for the generation of reactive compounds. The design of photochemically generated catalysts requires a deeper insight in the photochemistry in general. The choice of appropriate light-sensitive precursors can be guided by several considerations. A straight-forward approach involves the selection of compounds according to the type of electronic excitation which often predetermines the nature of the photoproducts.In a metal complex the metal-ligand bonds are generally polar. The molecular orbitals are then not equally delocalized between metal and ligands but predominantly located at the metal or the ligands. The electronic transitions are classified according to this localization [1]. In simple homoleptic mononuclear complexes three types of electronic excitations can be distinguished. Electronic transitions are localized at the metal (metalcentered, MC), at the ligand (ligand-centered, LC or intraligand, IL) or they take place between MOs at the metal and the ligand. The latter transitions are associated with a spatial redistribution of electrons and therefore are termed charge transfer (CT) transitions. While this review deals with CT excited states let us first have a short look at MC and LC states and their significance for the generation of reactive species which might be catalytically active.Since the valence orbitals of metals may be of the s, p, d, and f type all these orbitals can be involved in MC transitions. Ligand field (LF) or dd excited states have been investigated in great detail [2][3][4][5][6]. In many cases LF (or dd) excitation leads to a weakening of metal-ligand bonds. As a result a ligand may be released without any change of the oxidation state of the metal. This process is very important for the generation of catalysts because the product is a coordinatively unsaturated complex which provides an

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Section: Emission From Charge Transfer Statesmentioning

confidence: 99%

Section: Emission From Charge Transfer Statesmentioning

confidence: 99%

Section: Formation Of Solvated Electrons/reduction Of the Solventmentioning

confidence: 99%

Section: Formation Of Solvated Electrons/reduction Of the Solventmentioning

confidence: 99%

“…Ligand field (LF) or dd excited states have been investigated in great detail [2][3][4][5][6]. In many cases LF (or dd) excitation leads to a weakening of metal-ligand bonds.…”

mentioning

confidence: 99%

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