PubMed Health⌕ Search

Biomedical subjects

Mark M Richter

Publications and source records attributed to Mark M Richter.

11 recordsLinked to original sources
PubMed2006

Electrogenerated chemiluminescence of the lithium salts of 8-hydroxyquinoline and 2-methyl-8-hydroxyquinoline.

The spectroscopy, electrochemistry, and electrogenerated chemiluminescence (ECL) of [(q)(qH)Li]x (qH=8-hydroxyquinolinato) and [(Meq)(MeqH)Li]x (MeQH=2-methyl-8-hydroxyquinolinato) have been investigated. In both acetonitrile and aqueous solutions, [(q)(qH)Li]x and [(Meq)(MeqH)Li]x have absorption maxima at 320 and 309 nm, respectively. When excited at these wavelengths, the complexes emit around 500 nm (blue-green) in acetonitrile. Photoluminescence efficiencies (phiem) were 0.036 for [(q)(qH)Li]x and 0.012 for [(Meq)(MeqH)Li]x when compared to Ru(bpy)3(2+) (bpy=2,2'-bipyridine) with phiem=0.042. No photoluminescence was observed in aqueous media. The complexes show irreversible oxidative electrochemistry and quasi-reversible reductions in acetonitrile. ECL efficiencies (phiecl) were 0.097 for [(q)(qH)Li]x and 0.080 for [(Meq)(MeqH)Li]x when compared to Ru(bpy)(3)2+ (phiecl=1) in aqueous buffered solution and 0.035 for [(q)(qH)Li]x and 0.028 for [(Meq)(MeqH)Li]x in acetonitrile (0.05 M tri-n-propylamine (TPrA) as an oxidative-reductive ECL co-reactant). The ECL peaks at a potential corresponding to oxidation of both the TPrA and [(q)(qH)Li]x or [(Meq)(MeqH)Li]x. Also, qualitative studies using transmission filters suggest that both complexes emit ECL in approximately the same blue-green region as their photoluminescence, indicating that the same excited state is formed in both experiments.

Journal Article↗
PubMed2003

Electrochemiluminescence of tris(8-hydroxyquinoline-5-sulfonic acid)aluminum(III) in aqueous solution.

The electrochemiluminescence (ECL) of tris(8-hydroxyquinoline-5-sulfonic acid)aluminum(III) in aqueous solution is reported. ECL is generated by complexing aluminum ions with the chelating agent 8-hydroxyquinoline-5-sulfonic acid (HQS) to form Al(HQS)3, followed by oxidation in the presence of tri-n-propylamine (TPrA). The ECL intensity peaks a potential corresponding to oxidation of both TPrA and Al(HQS)3, and the ECL emission spectrum (lambda(max) = 499 nm) matches the photoluminescence emission spectrum, indicating that the emission is from a Al(HQS)3* excited state. ECL efficiencies (phi(ecl), photons generated per redox event) of 0.002 using Ru(bpy)3(2+) (phi(ecl) = 1) as relative standard. Conditions for ECL emission were optimized and used to generate a calibration curve that was linear over the 7 x 10(-6)-4 x 10(-4) M (5-281 mg/L (ppm)) range with a theoretical limit of detection of 1 ppm. The ECL of several metal ions other than aluminum with HQS and effects on Al(HQS)3 ECL were also examined.

Journal Article↗
PubMed2003

Effects of poly(ethylene glycol) tert-octylphenyl ether on tris(2-phenylpyridine)iridium(III)-tripropylamine electrochemiluminescence.

The effects of the nonionic surfactant Triton X-100 (poly(ethylene glycol) tert-octylphenyl ether) on the properties of tris(2-phenylpyridine)iridium(III) (Ir(ppy)3, where ppy = 2-phenylpyridine, electrochemiluminescence (ECL) have been investigated. Anodic oxidation of Ir(ppy)3 produces ECL in the presence of tri-n-propylamine (TPrA) in aqueous surfactant solution. Increases in ECL efficiency (> or = 10-fold) and TPrA oxidation current (> or = 2.0-fold) have been observed in surfactant media. The data support adsorption of surfactant on the electrode surface, thus facilitating TPrA and Ir(ppy)3 oxidation and leading to higher ECL efficiencies.

Journal Article↗
PubMed2002

Electrochemiluminescence from Os(phen)2(dppene)2+ (phen = 1,10-phenanthroline and dppene = bis(diphenylphosphino)ethene).

The electrochemiluminescence (ECL) of Os(phen)2(dppene)2+ (phen = 1,10-phenanthroline and dppene = bis(diphenylphosphino)ethene) is reported in mixed CH3CN/H2O (50:50 v/v) and aqueous (0.1 M KH2PO4) solutions with tri-n-propylamine (TPrA) as an oxidative-reductive coreactant. ECL efficiencies (phi(ecl) = photons emitted/redox event) of 2.0 in aqueous, and 0.95 in mixed for Os(phen)2(dppene)2+ were obtained using Ru(bpy)3(2+) (bpy = 2,2'-bipyridine) as a relative standard (phi(ecl) = 1). Photoluminescence (PL) efficiencies of 0.094 and 0.053 were obtained in aqueous and mixed solutions, respectively, as compared to Ru(bpy)3(2+) (phi(em) = 0.042). The ECL spectra were identical to photoluminescence spectra (lambda(max) approximately 584 nm), indicating formation of the same metal-to-ligand (MLCT) excited states in both ECL and PL. The ECL is linear over several orders of magnitude in aqueous and mixed solution, with theoretical detection limits (blank plus three times the standard deviation of the noise) of 16.9 nM in H2O and 0.29 nM in CH3CN/H2O (50:50 v/v).

Journal Article↗
PubMed2002

Green electrochemiluminescence from ortho-metalated tris(2-phenylpyridine)iridium(III).

The electrochemiluminescence (ECL) of Ir(ppy)3 (ppy = 2-phenylpyridine) is reported in acetonitrile (CH3CN), mixed CH3CN/H20 (50:50 v/v), and aqueous (0.1 M KH2PO4) solutions with tri-n-propylamine as an oxidative-reductive coreactant. ECL efficiencies (phi(ecl), photons emitted per redox event) of 0.00092 in aqueous, 0.0044 in mixed, and 0.33 in CH3CN solutions for Ir(ppy)3 were obtained using Ru(bpy)3(2+) (bpy = 2,2'-bipyridine) as a relative standard (phi(ecl) = 1). Photoluminescence (PL) efficiencies of 0.039, 0.050, and 0.069 were obtained in aqueous, mixed, and acetonitrile solutions, respectively, compared to Ru(bpy)3(2+) (phi(em) = 0.042). The ECL spectra were identical to photoluminescence spectra (lambda(max) approximately equal to 517 nm), indicating formation of the same metal-to-ligand (MLCT) excited states in both ECL and PL. The ECL is linear over several orders of magnitude in mixed and acetonitrile solution with theoretical detection limits (blank plus three times the standard deviation of the noise) of 1.23 nM in CH3CN and 0.23 microM in CH3CN/ H20 (50:50 v/v).

Journal Article↗
PubMed2002

Electrochemiluminescent detection of metal cations using a ruthenium(II) bipyridyl complex containing a crown ether moiety.

The effects of metal ions on the electrochemiluminescence (ECL) properties of (bpy)2Ru(AZA-bpy) (bpy = 2,2'-bipyridine; AZA-bpy = 4-(N-aza-18-crown-6-methyl-2,2'-bipyridine) have been investigated. The electrochemistry, photophysics and ECL of Ru(bpy)3(2+) in the presence of Pb2+, Hg2+, Cu2+, and K+ are reported. The anodic oxidation of Ru(bpy)3(2+) produces ECL in the presence of tri-n-propylamine (TPrA) in 50:50 (v/v) CH3CN:H2O solution. Increases in ECL efficiency (photons generated per redox event) up to 20-fold that depend on both the concentration and nature of the metal ion have been observed, making this an interesting system for electrochemiluminescence metal ion sensing.

Journal Article↗
PubMed2002

Effects of electron withdrawing and donating groups on the efficiency of tris(2,2'-bipyridyl)ruthenium(II)/tri-n-propylamine electrochemiluminescence.

The effects of electron withdrawing and electron donating groups on the electrochemiluminescent (ECL) properties of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3(2+) where bpy = 2,2'-pyridine) are reported. The electrochemistry, photophysics and ECL of (bpy)2Ru(DC-bpy)2+, and (bpy)2Ru(DM-bpy)2+ (DC = 4,4'-dicarboxy-2,2'-bipyridine; DM = 4,4'-dimethyl-2,2'-bipyridine) have been studied relative to Ru(bpy)3(2+) in 50:50 (v/v) acetonitrile(CH3CN):H2O (0.1 M KH2PO4), and aqueous solutions. Furthermore, the effects of Triton X-100 (polyethylene glycol tert-octylphenyl ether) on the electrochemical, spectroscopic and ECL properties of these compounds are reported. The anodic oxidation of Ru(bpy)3(2+), (bpy)2Ru(DC-bpy)2+, and (bpy)2Ru(DM-bpy)2+ produces ECL in the presence of tri-n-propylamine (TPrA) in all solvent systems. ECL efficiencies (phi(ecl), photons produced per redox event) of 0.73 and 0.84 for (bpy)2Ru(DC-bpy)2+, and (bpy)2Ru(DM-bpy)2+ were obtained in aqueous buffered solution, using Ru(bpy)3(2+) as a relative standard (phi(ecl) = 1.0). Addition of 0.4 mM Triton X-100 results in a greater than 2-fold increase in ECL efficiences (i.e., 3.8, 2.4 and 2.3 for Ru(bpy)3(2+), (bpy)2Ru(DC-bpy)2+, and (bpy)2Ru(DM-bpy)2+, respectively) using aqueous Ru(bpy)3(2+) containing no surfactant as standard (phi(ecl) = 1.0). ECL efficiencies of 27.4, 16.5 and 26.1 were found in 50:50 (v/v) CH3CN:H2O (0.1 M KH2PO4) for Ru(bpy)3(2+), (bpy)2Ru(DC-bpy)2+, and (bpy)2Ru(DM-bpy)2+, respectively, using aqueous Ru(bpy)3(2+) containing no surfactant as standard (phi(ecl) = 1.0). Detailed studies support adsorption of surfactant on the electrode surface, thus facilitating TPrA and ruthenium oxidation.

Journal Article↗
PubMed2002

Electrochemiluminescence in aqueous solution of a ruthenium(II) bipyridyl complex containing a crown ether moiety in the presence of metal ions.

Changes in electrochemiluminescence (ECL) properties of a ruthenium polyazine compound containing a crown-ether moiety have been investigated in aqueous buffered solution. The electrochemistry, photophysics and ECL of (bpy)2Ru(AZA-bpy)2+ [bpy = 2,2'-bipyridine; AZA-bpy = 4-(N-aza-18-crown-6-methyl-2,2'-bipyridine)] in the presence of Pb2+, Hg2+, Cu2+ and Ag+ are reported. Oxidation of (bpy)2Ru(AZA-bpy)2+ produces ECL in the presence of tri-n-propylamine (TPrA; 0.2 M KH2PO4). Increases in ECL efficiency (photons generated per redox event) greater than 2-fold have been observed that depend on both the concentration and nature of the metal ion, allowing the determination of ions not directly involved in the ECL reaction sequence.

Journal Article↗
PubMedDate not supplied

Electrogenerated chemiluminescence from polymer-bound ortho-metallated iridium(III) systems.

Three ortho-metallated iridium complexes whose emission maxima fall in different regions of the electromagnetic spectrum were bound in either Nafion or poly(9-vinylcarbazole) and their electrogenerated chemiluminescence (ECL) reported. The reaction of F(Ir)pic [bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)-iridium III] with the oxidative-reductive co-reactant tri-n-propylamine (TPrA) resulted in ECL when the iridium complex was bound in Nafion. No significant ECL was observed for (btp)(2)Ir(acac) (bis[2,(2'-benzothienyl)-pyridinato-N,C3'](acetylacetonate)Ir(III)), and Ir(ppy)(3) (where ppy = 2-phenylpyridine) under these conditions. However, all three compounds displayed ECL with TPrA when bound in poly(9-vinylcarbazole).

Cations↗
PubMedDate not supplied

Electrochemiluminescence of dipicolinic acid (DPA) and (bpy)(2)Ru(DPA)(+) (bpy = 2,2'-bipyridine).

The spectroscopic and electrochemiluminescence (ECL) properties of dipicolinic acid (DPA), (bpy)(2)Ru(2+) (bpy = 2,2'-bipyridine) and the species formed when DPA and (bpy)(2)Ru(2+) [abbreviated to (bpy)(2)Ru(DPA)(+)] are allowed to react are reported. The UV-Vis absorption maxima for (bpy)(2)Ru(2+) and (bpy)(2)Ru(DPA)(+) are 493 and 475 nm, respectively, indicating the in situ formation of a complex between DPA and (bpy)(2)Ru(2+). DPA, (bpy)(2)Ru(2+) and (bpy)(2)Ru(DPA)(+) display ECL upon oxidation in the presence of the oxidative-reductive co-reactant tri-n-propylamine (TPrA). The ECL of (bpy)(2)Ru(DPA)(+) is at least two-fold higher than either of the parent species. An ECL spectrum of (bpy)(2)Ru(DPA)(+) displays a peak maximum 40 nm red-shifted from the photoluminescence peak maximum, suggesting that the excited state formed electrochemically is different from that formed spectroscopically.

Absorption↗