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1.
Chemistry ; 20(13): 3652-66, 2014 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-24615869

RESUMO

A series of 2,5-bis(arylethynyl)rhodacyclopentadienes has been prepared by a rare example of regiospecific reductive coupling of 1,4-(p-R-phenyl)-1,3-butadiynes (R=H, Me, OMe, SMe, NMe2, CF3, CO2Me, CN, NO2, -C≡C-(p-C6H4-NHex2), -C≡C-(p-C6H4-CO2Oct)) at [RhX(PMe3)4] (1) (X=-C≡C-SiMe3 (a), -C≡C-(p-C6H4-NMe2) (b), -C≡C-C≡C-(p-C6H4-NPh2) (c) or -C≡C-{p-C6H4-C≡C-(p-C6H4 -N(C6H13)2)} (d) or Me (e)), giving the 2,5-bis(arylethynyl) isomer exclusively. The rhodacyclopentadienes bearing a methyl ligand in the equatorial plane (compound 1 e) have been converted into their chloro analogues by reaction with HCl etherate. The rhodacycles thus obtained are stable to air and moisture in the solid state and the acceptor-substituted compounds are even stable to air and moisture in solution. The photophysical properties of the rhodacyclopentadienes are highly unusual in that they exhibit, exclusively, fluorescence between 500-800 nm from the S1 state, with quantum yields of Φ=0.01-0.18 and short lifetimes (τ=0.45-8.20 ns). The triplet state formation (Φ(ISC) =0.57 for 2 a) is exceptionally slow, occurring on the nanosecond timescale. This is unexpected, because the Rh atom should normally facilitate intersystem crossing within femto- to picoseconds, leading to phosphorescence from the T1 state. This work therefore highlights that in some transition-metal complexes, the heavy atom can play a more subtle role in controlling the photophysical behavior than is commonly appreciated.

2.
Photochem Photobiol Sci ; 13(1): 62-9, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24196234

RESUMO

Photophysical and photochemical measurements have been made on a series of novel alpha octa(alkyl-substituted) silicon, zinc and palladium phthalocyanines for which the synthesis is outlined. Fluorescence quantum yields and lifetimes, triplet quantum yields and lifetimes and singlet delta oxygen quantum yields were measured in 1% v/v pyridine in toluene. The effects of varying central atom and addition of alkyl substituents relative to unsubstituted parent molecules, zinc phthalocyanine (ZnPc) and silicon phthalocyanine (SiPc), are discussed. All phthalocyanines studied exhibit absorption and emission maxima in the region of 680-750 nm with molar absorptivity of the Q-band ~10(5) M(-1) cm(-1). The series of compounds also exhibited triplet quantum yields of 0.65-0.95 and singlet oxygen quantum yields of 0.49-0.93.

3.
Photochem Photobiol Sci ; 9(3): 370-5, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20221464

RESUMO

Photophysical and photochemical measurements have been made on a series of novel non-peripherally octa(alkyl-substituted) zinc phthalocyanines. Fluorescence quantum yields and lifetimes, triplet quantum yields and lifetimes and singlet delta oxygen quantum yields were measured in 1% v/v pyridine in toluene. The effects of alkyl substituents and increasing chain length relative to the unsubstituted parent molecule, zinc phthalocyanine (ZnPc), are discussed. ZnPc with alkyl substituents of chain length 5-15 carbons exhibited similar absorption and emission maxima (704 nm and 718 nm respectively) with the molar absorptivity of the Q-band approximately 10(5) M(-1) cm(-1). The series of compounds also exhibited triplet quantum yields of 0.78-0.84 and singlet oxygen quantum yields of 0.67-0.71.


Assuntos
Indóis/química , Compostos Organometálicos/química , Fotoquímica , Espectrofotometria
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