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Titolo:
Photoinduced charge separation at room temperature of N-alkylpyrenes in transition metal ion containing mesoporous SiMCM-41 and MeMCM-41 silica molecular sieves where Me = Ti(IV), V(V), Ni(II), Co(II) and Cu(II)
Autore:
Krishna, RM; Kevan, L;
Indirizzi:
Univ Houston, Dept Chem, Houston, TX 77204 USA Univ Houston Houston TX USA 77204 uston, Dept Chem, Houston, TX 77204 USA
Titolo Testata:
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
fascicolo: 23, volume: 3, anno: 2001,
pagine: 5348 - 5353
SICI:
1463-9076(2001)3:23<5348:PCSART>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
ELECTRON-SPIN-RESONANCE; ECHO MODULATION SPECTROSCOPIES; DIFFERENT PORE SIZES; CONTAINING MCM-41; ARTIFICIAL PHOTOSYNTHESIS; PARAMAGNETIC-RESONANCE; PHOTOIONIZATION; ENERGY; METHYLPHENOTHIAZINE; ALKYLPHENOTHIAZINES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
43
Recensione:
Indirizzi per estratti:
Indirizzo: Kevan, L Univ Houston, Dept Chem, Univ Pk, Houston, TX 77204 USA Univ Houston Univ Pk Houston TX USA 77204 , Houston, TX 77204 USA
Citazione:
R.M. Krishna e L. Kevan, "Photoinduced charge separation at room temperature of N-alkylpyrenes in transition metal ion containing mesoporous SiMCM-41 and MeMCM-41 silica molecular sieves where Me = Ti(IV), V(V), Ni(II), Co(II) and Cu(II)", PHYS CHEM P, 3(23), 2001, pp. 5348-5353

Abstract

The photoinduced charge separation of N-alkylpyrenes in transition metal ion containing mesoporous SiMCM-41 and MeMCM-41 materials [Me = Ti(IV), V(V), Ni(II), Co(II) and Cu(II)] with ultraviolet irradiation at room temperature is investigated. N-alkylpyrene cation radicals (PyCn+) are generated in SiMCM-41 and MeMCM-41 mesoporous silica materials and are characterized by electron spin resonance (ESR) spectroscopy. Mesoporous SiMCM-41 and MeMCM-41 materials are shown to be effective heterogeneous hosts for the photoinduced formation and stabilization of PyCn+ cation radicals at room temperature indicating stable photoinduced charge separation for several hours. The long lifetimes for the cation radicals indicate the utility of the environment of these MCM-41 materials for controlling back electron transfer. A series of TiMCM-41 materials are synthesized that increase the PyCn+ photoionization efficiency in comparison with VMCM-41, NiMCM-41, CoMCM-41 and CuMCM-41. The photoyield efficiency is decreased significantly when the concentration of pyrene is increased above about 10(-2) M. The photoionization efficiency depends on the type and concentration of the metal ions in the mesoporous MeMCM-41 materials which suggests that certain metal ions can act as electron acceptors. Also, as the N-alkylpyrene alkyl chain length increases from methyl to hexadecyl the photoionization yield decreases. The photoionization efficiency increases in the order TiMCM-41 > NiMCM-41 > VMCM-41 > SiMCM-41 > CoMCM-41 > CuMCM-41. The photoyield is higher by about 1.5 times at77 K compared to room temperature. The observed photoyields of PyCn (n = 1, 4, 8, 12, or 16) in mesoporous MeMCM-41 materials suggest that these materials are useful models for long-term photoinduced charge separation at room temperature.

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Documento generato il 02/07/20 alle ore 19:21:34