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Martin Devenney

Publications and source records attributed to Martin Devenney.

4 recordsLinked to original sources
PubMed1999

Excited-State Electron Transfer in a Chromophore-Quencher Complex. Spectroscopic Identification of a Redox-Separated State.

In the chromophore-quencher complex fac-[Re(Aqphen)(CO)(3)(py-PTZ)](+) (Aqphen is 12,17-dihydronaphtho[2,3-h]dipyrido[3,2-a:2',3'-c]-phenazine-12,17-dione; py-PTZ is 10-(4-picolyl)phenothiazine), Aqphen is a dppz derivative, containing a pendant quinone acceptor at the terminus of a rigid ligand framework. This introduces a third, low-lying, ligand-based pi acceptor level localized largely on the quinone fragment. Laser flash excitation of fac-[Re(Aqphen)(CO)(3)(py-PTZ)](+) (354.7 nm; in 1,2-dichloroethane) results in the appearance of a relatively long-lived transient that decays with tau(298K) = 300 ns (k = 3.3 x 10(6) s(-)(1)). Application of transient absorption, time-resolved resonance Raman, and time-resolved infrared spectroscopies proves that this transient is the redox-separated state fac-[Re(I)(Aqphen(*)(-)())(CO)(3)(py-PTZ(*)(+)())](+) in which the excited electron is localized largely on the quinone portion of the Aqphen ligand.

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PubMed1998

Electropolymerized Films of Macromeric Assemblies.

The polymer poly[4-(2-aminoethyl)styrene], prepared by living anionic polymerization, has been derivatized by amide coupling to [Ru(II)(vbpy)(2)(4-CO(2)H-4'-CH(3)bpy)](2+) (vbpy is 4-vinyl-4'-methyl-2,2'-bipyridine; 4-CO(2)H-4'-CH(3)bpy is 4-methyl-2,2'-bipyridine-4'-carboxylic acid). The resulting "macromer" can be electropolymerized on a variety of electrode materials by reductive electropolymerization. Compared to similar films of poly[Ru(II)(vbpy)(3)](PF(6))(2): (1) the macromeric films are considerably rougher, apparently having open, local microporous structures; (2) they undergo comparable rates of intrafilm charge transfer; and (3) they have shortened metal-to-ligand charge transfer (MLCT) excited state lifetimes, apparently due to quenching by film-based trap sites. Stable films of a mixed polymer have also been prepared by sequential addition of [Ru(II)(bpy)(2)(4-CO(2)H-4'-CH(3)bpy)](2+) and then the vbpy derivative.

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PubMed1997

Osmium Hydrazido and Dinitrogen Complexes.

[Os(tpy)(bpy)(NH(3))](PF(6))(2) (1) was oxidized electrochemically in the presence of a series of amines in aqueous solutions buffered to pH 7. With secondary aliphatic amines, electrolysis gave [Os(tpy)(bpy)(NNR(2))](PF(6))(3) (3); number of electrons n = 4.6-5.0. 3 was reduced to [Os(tpy)(bpy)(NNR(2))](PF(6))(2) (2) in aqueous and nonaqueous solutions with n = 1.0. The structures of 2 were determined by X-ray crystallography for NR(2) = diethylamide (2a) and morpholide (2c) and were found to exhibit bent hydrazido(2-) coordination (Os-N-N = 137 degrees ). The salts crystallized in the triclinic system, space group P&onemacr;. For 2a, a = 9.004(1) Å, b = 9.796(1) Å, c = 20.710(2) Å, alpha = 88.78(2) degrees, beta = 85.43(2) degrees, gamma = 86.22(2) degrees, and Z = 2. For 2c, a = 9.632(8) Å, b = 21.229(9) Å, c = 9.039(5) Å, alpha = 97.41(4) degrees, beta = 94.28(5) degrees, gamma = 85.07(5) degrees, and Z = 2. Solutions of 2 were protonated in strongly acidic media to give hydrazido(1-) complexes. The pK(a) of the protonated form of 2a is 0.90 +/- 0.01. Reduction of 2 in aqueous solutions of pH <1 gave 1 and NH(2)R(2)(+) with n = 4.0. At higher pH, there is evidence for an Os(II) hydrazine intermediate. Oxidation of 3 by one electron afforded transiently stable species which decomposed to give [Os(tpy)(bpy)(NCCH(3))](3+) in acetonitrile solution. Pseudo-first-order rate constants of 8.1 +/- 0.9 s(-)(1) and 0.200 +/-.005 s(-)(1) were estimated by cyclic voltammetry on solutions of 2a and 2b(NR(2) = piperidide), respectively. Oxidation of 1 at pH 7, in the presence of primary aliphatic amines or ammonia, occurred with n = 5.9-6.2, and generated [Os(II)(tpy)(bpy)(N(2))](PF(6))(2) (4).

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