Ligand substitution, pH dependent deoxygenation, and linkage isomerization reactions of the 2,2'-bipyridinetetranitroruthenate dianion

High thermal stability of the Ru–ON (MS1) linkage isomer of the ruthenium nitrosyl complex [RuNO(Py)4F](ClO4)2 with the trans NO–Ru–F coordinate

The [RuNO(Py)₄F](ClO₄)₂ complex with the highest thermal stability of the Ru–ON linkage isomer.

Preparation, separation, and characterization of ruthenium(II) thiocyanate linkage isomers

The reaction of [(p-cym)Ru(bpy)Cl](+) (p-cym = eta(6)-p-cymene; bpy = 2,2'-bipyridine) with SCN(-) gives a mixture of the linkage isomers [(p-cym)Ru(bpy)(SCN)](+) and [(p-cym)Ru(bpy)(NCS)](+). The linkage isomers were efficiently separated by column chromatography on Hg(NO3)2-coated Al2O3. Both isomers were fully characterized by elemental analysis, (1)H NMR and IR spectroscopy, and X-ray crystallography. The equilibrium constant for the conversion of the S-bound to the N-bound isomer was determined to be 0.29(4) in methanol-d4 and 0.74(7) in acetone-d6, respectively, at 50 degrees C. Kinetic data for the linkage isomerization reaction are also reported.

Synthesis, characterization, and reactivity of [Ru(bpy)(CH3CN)3(NO2)]PF6, a synthon for [Ru(bpy)(L3)NO2] complexes

We report a high yield, two-step synthesis of fac-[Ru(bpy)(CH3CN)3NO2]PF6 from the known complex [(p-cym)Ru(bpy)Cl]PF6 (p-cym = eta(6)-p-cymene). [(p-cym)Ru(bpy)NO2]PF6 is prepared by reacting [(p-cymene)Ru(bpy)Cl]PF6 with AgNO3/KNO2 or AgNO2. The 15NO2 analogue is prepared using K15NO2. Displacement of p-cymene from [(p-cym)Ru(bpy)NO2]PF6 by acetonitrile gives [Ru(bpy)(CH3CN)3NO2]PF6. The new complexes [(p-cym)Ru(bpy)NO2]PF6 and fac-[Ru(bpy)(CH3CN)3NO2]PF6 have been fully characterized by 1H and 15N NMR, IR, elemental analysis, and single-crystal structure determination. Reaction of [Ru(bpy)(CH3CN)3NO2]PF6 with the appropriate ligands gives the new complexes [Ru(bpy)(Tp)NO2] (Tp = HB(pz)3-, pz = 1-pyrazolyl), [Ru(bpy)(Tpm)NO2]PF6 (Tpm = HC(pz)3), and the previously prepared [Ru(bpy)(trpy)NO2]PF6 (trpy = 2,2',6',2' '-terpyridine). Reaction of the nitro complexes with HPF6 gives the new nitrosyl complexes [Ru(bpy)TpNO][PF6]2 and [Ru(bpy)(Tpm)NO][PF6]3. All complexes were prepared with 15N-labeled nitro or nitrosyl groups. The nitro and nitrosyl complexes were characterized by 1H and 15N NMR and IR spectroscopy, elemental analysis, cyclic voltammetry, and single-crystal structure determination for [Ru(bpy)TpNO][PF6]2. For the nitro complexes, a linear correlation is observed between the nitro 15N NMR chemical shift and 1/nu(asym), where nu(asym) is the asymmetric stretching frequency of the nitro group.

Ruthenium Nitrosyls Derived from Polypyridine Ligands with Carboxamide or Imine Nitrogen Donor(s): Isoelectronic Complexes with Different NO Photolability

As part of our search for photoactive ruthenium nitrosyls, a set of {RuNO}6 nitrosyls has been synthesized and structurally characterized. In this set, the first nitrosyl [(SBPy3)Ru(NO)](BF4)3 (1) is derived from a polypyridine Schiff base ligand SBPy3, while the remaining three nitrosyls are derived from analogous polypyridine ligands containing either one ([(PaPy3)Ru(NO)](BF4)2 (2)) or two ([(Py3P)Ru(NO)]BF4 (3) and [(Py3P)Ru(NO)(Cl)] (4)) carboxamide group(s). The coordination structures of 1 and 2 are very similar except that in 2, a carboxamido nitrogen is coordinated to the ruthenium center in place of an imine nitrogen in case of 1. In 3 and 4, the ruthenium center is coordinated to two carboxamido nitrogens in the equatorial plane and the bound NO is trans to a pyridine nitrogen (in 3) and chloride (in 4), respectively. Complexes 1-3 contain N6 donor set, and the NO stretching frequencies (nuNO) correlate well with the N-O bond distances. All four diamagnetic {RuNO}(6) nitrosyls are photoactive and release NO rapidly upon illumination with low-intensity (5-10 mW) UV light. Interestingly, photolysis of 1 generates the diamagnetic Ru(II) photoproduct [(SBPy3)Ru(MeCN)](2+) while 2-4 afford paramagnetic Ru(III) species in MeCN solution. The quantum yield values of NO release under UV illumination (lambda(max) = 302 nm) lie in the range 0.06-0.17. Complexes 3 and 4 also exhibit considerable photoactivity under visible light. The efficiency of NO release increases in the order 2 < 3 < 4, indicating that photorelease of NO is facilitated by (a) the increase in the number of coordinated carboxamido nitrogen(s) and (b) the presence of negatively charged ligands (like chloride) trans to the bound NO.

Effect of potassium-enriched salt on cardiovascular mortality and medical expenses of elderly men

BACKGROUND

The beneficial effects of potassium-enriched salt on blood pressure have been reported in a few short-term trials. The long-term effects of potassium-enriched salt on cardiovascular mortality have not been carefully studied.

OBJECTIVE

The objective was to examine the effects of potassium-enriched salt on cardiovascular disease (CVD) mortality and medical expenditures in elderly veterans.

DESIGN

Five kitchens of a veteran retirement home were randomized into 2 groups (experimental or control) and veterans assigned to those kitchens were given either potassium-enriched salt (experimental group) or regular salt (control group) for approximately 31 mo. Information on death, health insurance claims, and dates that veterans moved in or out of the home was gathered.

RESULTS

Altogether, 1981 veterans, 768 in the experimental [x (+/-SD) age: 74.8 +/- 7.1 y] and 1213 in the control (age: 74.9 +/- 6.7 y) groups, were included in the analysis. The experimental group had better CVD survivorship than did the control group. The incidence of CVD-related deaths was 13.1 per 1000 persons (27 deaths in 2057 person-years) and 20.5 per 1000 (66 deaths in 3218 person-years) for the experimental and control groups, respectively. A significant reduction in CVD mortality (age-adjusted hazard ratio: 0.59; 95% CI: 0.37, 0.95) was observed in the experimental group. Persons in the experimental group lived 0.3-0.90 y longer and spent significantly less (approximately US Dollars 426/y) in inpatient care for CVD than did the control group, after control for age and previous hospitalization expenditures.

CONCLUSIONS

This study showed a long-term beneficial effect on CVD mortality and medical expenditure associated with a switch from regular salt to potassium-enriched salt in a group of elderly veterans. The effect was likely due to a major increase in potassium and a moderate reduction in sodium intakes.

A New Approach for Studying Fast Biological Reactions Involving Nitric Oxide: Generation of NO Using Photolabile Ruthenium and Manganese NO Donors

Nitric oxide (NO) is recognized as one of the major players in various biochemical processes, including blood pressure, neurotransmission and immune responses. However, experimental studies involving NO are often limited by difficulties associated with the use of NO gas, including its toxicity and precise control over NO concentration. Moreover, the reactions of NO with biological molecules, which frequently occur on time scales of microseconds or faster, are limited by the millisecond time scale of conventional stopped-flow techniques. Here we present a new approach for studying rapid biological reactions involving NO. The method is based on designed ruthenium and manganese nitrosyls, [Ru(PaPy3)(NO)](BF4)2 and [Mn(PaPy3)(NO)](ClO4) (PaPy3H = N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamide), which upon photolysis produce NO on a fast time scale. The kinetics of the binding of the photogenerated NO to reduced cytochrome c oxidase (CcO) and myoglobin (Mb) was investigated using time-resolved optical absorption spectroscopy. The NO was found to bind to reduced CcO with an apparent lifetime of 77 micros using the [Mn(PaPy3)(NO)]+ complex; the corresponding rate is 10-20 times faster than can be detected by conventional stopped-flow methods. Second-order rate constants of approximately 1 x 10(8) M(-1) s(-1) and approximately 3 x 10(7) M(-1) s(-1) were determined for NO binding to reduced CcO and Mb, respectively. The generation of NO by photolysis of these complexes circumvents the rate limitation of stopped-flow techniques and offers a novel alternative to study other fast biological reactions involving NO.