Details

Autor(en) / Beteiligte

• Alberding, Brian G
• Brown-Xu, Samantha E
• Chisholm, Malcolm H
• Gustafson, Terry L
• Reed, Carly R
• Naseri, Vesal

Titel

Photophysical properties of MM quadruply bonded complexes (M = Mo, W) supported by carboxylate ligands: charge delocalization and dynamics in S sub(1) and T sub(1) states

Ist Teil von

• Dalton transactions : an international journal of inorganic chemistry, 2012-10, Vol.41 (42), p.13097-13104

Erscheinungsjahr

2012

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Quadruply bonded dinuclear metal complexes of molybdenum and tungsten have the MM configuration sigma super(2) pi super(4) delta super(2) and a considerable degree of attention has been devoted to studies of the delta arrow right delta super(*) transition. For compounds of the type M sub(2)(O sub(2)CR) sub(4), the CO sub(2) pi super(*) orbitals introduce a M sub(2) delta to ligand pi super(*) transition, a super(1)MLCT absorption which may be lower in energy than the delta arrow right delta super(*) and is more intense, thus obscuring the observation of the latter. When the R group is a conjugated organic system such as an aryl group, the super(1)MLCT shifts to even lower energy and emission is seen from this S sub(1) state in addition to phosphorescence from the T sub(1) state which may be either super(3)MLCT or super(3)MM delta delta super(*). The latter typically occurs around 1100 nm with a lifetime that ranges from similar to 1 mu s (M = W) to 100 mu s (M = Mo). The S sub(1) super(1)MLCT states have lifetimes of similar to 1-20 ps, allowing for fs and ns studies of the charge distribution/localization with time in both the S sub(1) and T sub(1) states, which is quite rare for transition metal coordination complexes. Of particular interest and focus have been complexes of the type trans-M sub(2)L sub(2)L' sub(2) where L and L' are carboxylate or amidinate groups for which only one set of ligands allows for expansive L pi -M sub(2) delta -L pi conjugation and has a low energy super(1)MLCT. Compounds of this type have excited states that may be considered as mixed valence (MV) ions [L-M sub(2) super(+)-L super(-)] reversible reaction [L super(-)-M sub(2) super(+)-L] where the hole resides on the M sub(2) unit and the electron is either localized on one ligand, a class I or II MV ion, or is fully delocalized over both ligands, a class III ion in the Robin and Day scheme. Examples of these systems will be described along with the newly prepared complexes trans-M sub(2)(T super(i)PB) sub(2)(O sub(2)CC&z.tbd; C-9-anthracene) sub(2) , M = Mo, W, that have the IR-active reporter groups CO sub(2) and C&z.tbd; C.