Ivan M. Lorkovic

Photochemistry of metal nitrosyl complexes. Delivery of nitric oxide to biological targets

Abstract The discoveries that nitric oxide serves important roles in mammalian bioregulation and immunology have stimulated intense interest in the chemistry and biochemistry of NO and derivatives such as metal nitrosyl complexes. Also of interest are strategies to deliver NO to biological targets on demand. One such strategy would be to employ a precursor which displays relatively low thermal reactivity but is photochemically active to give NO. This proposition led the authors to investigate photochemical properties of metal nitrosyl complexes such as the iron-sulfur-nitrosyl Roussin cluster anions Fe2S2(NO)42− and Fe4S3(NO)7− as well as metalloporphyrin nitrosyls including ferriheme complexes (with M. Hoshino of the Institute of Physical and Chemical Research, Japan) and nitrosyl nitrito complexes of ruthenium porphyrins Ru(P)(ONO)(NO). Continuous and flash photolysis studies of these compounds are reviewed here as are studies (with D.A. Wink and J.B. Mitchell of the Radiation Biology Branch of the US National Cancer Institute) using metal nitrosyl photochemistry as a vehicle for delivering NO to hypoxic cell cultures in order to sensitize γ-radiation damage.

C1 Coupling via bromine activation and tandem catalytic condensation and neutralization over CaO/zeolite compositesElectronic supplementary information (ESI) available: additional figures. See http://www.rsc.org/suppdata/cc/b3/b314118g/

We demonstrate here an alternative scheme for C(1) coupling by way of methane bromination, followed by concurrent bromomethane condensation and quantitative HBr neutralization; regeneration of the metal oxide with O(2) with recovery of Br(2) completes the cycle.

REACTION MECHANISMS OF NITRIC OXIDE WITH BIOLOGICALLY RELEVANT METAL CENTERS

Publisher Summary This chapter reviews certain substitution and redox-mechanism studies involving the interaction of nitric oxide (NO) with transition-metal complexes with a view toward illustrating how these may be relevant to the known biological functions of NO in mammalian biology. NO is also very reactive with redox active metal centers, especially if these are ligand substitution labile. Substitution reactions of NO on metal centers as well as reactions with radical species generally display kinetic-rate laws that show a first-order dependence on [NO]. With respect to the bioregulatory roles of NO in blood-pressure control and neurological function, the principal action centers on the reaction with a metal center to form a nitrosyl complex, namely the activation of soluble guanylyl cyclase (sGC) by reaction with the iron(II) site of that ferroheme enzyme. There is also considerable biological interest in reactions of NO with ligands coordinated to a redox-active metal.

An integrated process for partial oxidation of alkanes

The partial oxidation of alkanes via bromination followed by the reaction with solid metal oxide mixtures (MO) is shown to give an array of products that can be tuned by varying the MO and the reaction conditions.

The Preparation of Anaerobic Nitric Oxide Solutions for the Study of Heme Model Systems in Aqueous and Nonaqueous Media: Some Consequences of NOx Impurities

The reactions of nitric oxide (NO) have been a subject of broad interest among biochemists and chemists. This report discusses several quantitative techniques to handle and use NO gas that has been delivered from compressed cylinders. The focus is on techniques that minimize and avoid the presence of oxygen impurities, which when present, result in the generation of other nitrogen oxides (NO x). These NO x species typically exhibit different reactivity, and unless removed or quantified, their presence will complicate studies focusing on the reactions caused by NO itself.

Evidence for a common Ru(P)(NO)2 intermediate in photochemical and synthesis pathways involving Ru(TmTP)(NO)(ONO) and excess nitric oxide

Optical and IR spectra of the intermediate formed from the reaction of Ru(CO)(TmTP) with NO are compared with transient UV–VIS and FTIR spectra of photochemical intermediates formed from the photolysis and recovery of Ru(TmTP)(NO)(ONO) in the presence of NO; comparison reveals that the two pathways share a common intermediate, which IR spectral properties suggest to be trans-Ru(TmTP)(NO)2.

Chapter 3 – NO and NOx Interactions with Hemes

In this chapter, we will discuss the mechanistic studies of NO and NO x ( NO 2 − , ⋅ NO 2 , N 2 O 3 , etc . ) reactions with heme proteins and heme model compounds, with the goal of providing further insight into the related reactions occurring in mammalian biology.

Synthesis and characterization of the dinuclear iron–sulfur cluster {bis[(1,1′-dithiolatoferrocene-μ-sulfido-ferrate(III)]}2−

Abstract The novel iron–sulfur cluster dimer {bis[(1,1′-dithiolatoferrocene-μ-sulfido-ferrate(III)]} 2− is prepared as the tetrapropylammonium salt in a one-pot synthesis from 1,1′-trithiaferrocenophane, FeCl 3 , and t BuS − . The X-ray crystallography, electronic spectroscopy, electrochemistry, and magnetic susceptibility of this complex are reported and compared and contrasted to previously prepared iron–sulfur dimer complexes with organic thiolate ligands.