RESUMEN
Phenanthroline ligands are important metal-binding mol-ecules which have been extensively researched for applications in both material science and medicinal chemistry. Azo-benzene and its derivatives have received significant attention because of their ability to be reversibly switched between the E and Z forms and so could have applications in optical memory and logic devices or as mol-ecular machines. Herein we report the formation and crystal structure of a highly unusual novel diazo-diphenanthroline compound, C24H14N6O2·2CHCl3.
RESUMEN
The photophysics and photochemistry of [(CO)5MC(OMe)Me] (M = Cr or W) were investigated using picosecond time-resolved infrared spectroscopy (M = Cr or W), low-temperature matrix isolation techniques (M = Cr), and time-dependent density functional calculations (M = Cr or W). These studies provide unambiguous evidence for the photochemical formation of a long-lived, 18-electron metallaketene species capable of acting as a synthetically useful intermediate. For the Cr complex, an intermediate metallacyclopropanone singlet excited state was detected on the reaction path to the metallaketene species. This metallacyclopropanone excited state species has a lifetime of less than 100 ps and a characteristic bridging carbonyl band at 1770 cm(-1). The tungsten ketene species was also detected but in contrast to the chromium system, this forms directly from a low-lying triplet excited state. The electrochemical release of CO showed a greater efficiency for the chromium complex when compared to the tungsten.
RESUMEN
Multimodal photo, thermal and electrochemical approaches toward CO release from the amino carbene complex [(CO)5CrC(NC4H8)CH3] is reported. Picosecond time resolved infrared spectroscopy was used to probe the photo-induced early state dynamics leading to CO release, and DFT calculations confirmed that CO release occurs from a singlet excited state.
Asunto(s)
Monóxido de Carbono/química , Cromo/química , Técnicas Electroquímicas , Metano/análogos & derivados , Compuestos Organometálicos/química , Temperatura , Metano/química , Procesos Fotoquímicos , Teoría CuánticaRESUMEN
The influence of the thiophene ring on the ground and excited state properties of the porphyrin ring is investigated, when substituted at the meso-position. A series of mono-, di-, tri-, and tetra- meso-thien-2-yl porphyrins are studied and discussed with respect to the reference compounds zinc(II)-5,10,15,20-tetra(thien-2'-yl)porphyrin ( 1a) and zinc(II)-5,10,15,20-tetraphenylporphyrin (ZnTPP). The extended conjugated system zinc(II)-5-(5'-(5''-ethynyl-2''-thiophenecarboxaldehyde)thien-2'-yl)-10,15,20-triphenylporphyrin ( 4d) is also studied and shows enhanced charge transfer character due to the presence of the terminal aldehyde accepting group. A detailed analysis of ground and excited state UV-vis absorption, steady-state and time-resolved fluorescence, laser flash photolysis, and electrochemical data all point toward substantial electronic communication between the central Zn(II) porphyrin ring and the meso-thien-2-yl substituents, which is evident from excited state charge transfer character.
Asunto(s)
Metaloporfirinas/química , Zinc/química , Absorción , Electroquímica , Fluorescencia , Espectroscopía de Resonancia Magnética , Espectrofotometría Ultravioleta , Factores de TiempoRESUMEN
The efficient on/off switching of fluorescence from thienyl- and phenyl-substituted porphyrin-ferrocene dyads is achieved through redox control of excited-state electron-transfer quenching.