A little spin on the side: solvent and temperature dependent paramagnetism in [Ru(II)(bpy)2(phendione)](2+).

Solvent and temperature dependent paramagnetism is reported for the complex [Ru(II)(bpy)2(phendione)](PF6)2 (bpy = 2,2'-bipyridine, phendione = 1,10-phenanthroline-5,6-dione), . Magnetometry, (1)H-NMR, EPR and substituent effects confirm that the paramagnetic character is localized on the phendione ligand, and arises due to mixing of the MLCT excited state with an open shell triplet state on the phendione moiety, a process that is most likely driven by aromatization. The stabilized open shell phendione structure, in which the triplet lies lower in energy than the singlet, can then be thermally populated from the ground state of the complex.

Spectroscopic studies of bridge contributions to electronic coupling in a donor-bridge-acceptor biradical system.

Variable-temperature electronic absorption and resonance Raman spectroscopies are used to probe the excited state electronic structure of Tp(Cum,Me)Zn(SQ-Ph-NN) (1), a donor-bridge-acceptor (D-B-A) biradical complex and a ground state analogue of the charge-separated excited state formed in photoinduced electron transfer reactions. Strong electronic coupling mediated by the p-phenylene bridge stabilizes the triplet ground state of this molecule. Detailed spectroscopic and bonding calculations elucidate key bridge distortions that are involved in the SQ(π)(SOMO) → NN-Ph (π*)(LUMO) D → A charge transfer (CT) transition.

Structural and pH dependence of excited state PCET reactions involving reductive quenching of the MLCT excited state of [RuII(bpy)2(bpz)]2+ by hydroquinones.

The proton-coupled electron transfer (PCET) reaction between the bpz-based photoexcited (3)MLCT state of [Ru(II)(bpy)(2)(bpz)](2+) (bpy = 2,2'-bipyridine, bpz = 2,2'-bipyrazine) and a series of substituted hydroquinones (H(2)Q) has been studied by transient absorption (TA) and time-resolved electron paramagnetic resonance (TREPR) spectroscopy at X-band. When the reaction is carried out in a CH(3)CN/H(2)O mixed solvent system with unsubstituted hydroquinone, the neutral semiquinone radical (4a) and its conjugate base, the semiquinone radical anion (4b), are both observed. Variation of the acid strength in the solvent mixture allows the acid/base dependence of the PCET reaction to be investigated.

Hyperfine interaction, spin polarization, and spin delocalization as probes of donor-bridge-acceptor interactions in exchange-coupled biradicals.

Computations and EPR spectroscopy are used to probe the spin distribution of donor-bridge-acceptor (D-B-A) biradical complexes: Tp(Cum,Me)Zn(SQ-NN) (1), Tp(Cum,Me)Zn(SQ-1,4-Ph-NN) (2), Tp(Cum,Me)Zn(SQ-2,5-TP-NN) (3), and Tp(Cum,Me)Zn(SQ-2,5-Xyl-NN) (4) (SQ = orthosemiquinone and NN = nitronylnitroxide). These complexes are ground-state analogs of the charge-separated excited states formed in photoinduced electron transfer reactions. The intraligand magnetic exchange interaction (J) in these complexes is mediated by the bridges and has been found to stabilize the triplet ground states of 1 and 2.

Outcome of a hepatitis C outbreak among patients in a pain management clinic.

Background And Aims: The aims of this study are to evaluate the natural history and response to therapy of patients following a hepatitis C outbreak in a pain management clinic.

Methods: A retrospective cohort study was conducted on patients who acquired hepatitis C virus (HCV) at a pain management clinic. Medical records were retrospectively reviewed for 77% of patients with hepatitis C included in the outbreak to obtain data regarding laboratory results, treatment, and outcomes.

Magnetic bistability in a cobalt bis(dioxolene) complex: long-lived photoinduced valence tautomerism.

The thermal- and photoinduced valence tautomerism of a cobalt bis(dioxolene) complex is described. The thermal conversion is precipitous, complete within 10 K, and is accompanied by a 5 K hysteresis loop (107 K < T(1/2) < 112 K). Rapid thermal quenching (300 K --> 10 K in ca.

Ferromagnetic nanoscale electron correlation promoted by organic spin-dependent delocalization.

We describe the electronic structure and the origin of ferromagnetic exchange coupling in two new metal complexes, NN-SQ-Co(III)(py)(2)Cat-NN (1) and NN-Ph-SQ-Co(III)(py)(2)Cat-Ph-NN (2) (NN = nitronylnitroxide radical, Ph = 1,4-phenylene, SQ = S = (1)/(2) semiquinone radical, Cat = S = 0 catecholate, and py = pyridine). Near-IR electronic absorption spectroscopy for 1 and 2 reveals a low-energy optical band that has been assigned as a Psi(u) --> Psi(g) transition involving bonding and antibonding linear combinations of delocalized dioxolene (SQ/Cat) valence frontier molecular orbitals. The ferromagnetic exchange interaction in 1 is so strong that only the high-spin quartet state (S(T) = (3)/(2)) is thermally populated at temperatures up to 300 K.

Direct amination of 1-substituted 3,5-dinitrobenzenes by 1,1,1-trimethylhydrazinium iodide.

The amination of 1-X-3,5-dinitrobenzenes via the vicarious nucleophilic substitution of hydrogen (VNS) with 1,1,1-trimethylhydrazinium iodide (TMHI) in the presence of t-BuOK or NaOMe in DMSO was studied. It was observed (when X = OMe, OCH(2)CF(3), OCH(2)CF(2)CF(2)H, OPh) that the amination occurs regioselectively (ratio of ortho/para-isomers is approximately 9:1) and with high yield. For X = SPh or SCH(2)Ph, the reaction proceeded with a low yield (less than 20%), with a ratio of ortho/para-isomers approximately 1:1.