Polypyridyl Bridging Ligands Research Articles

A new family of Ru(II) polypyridyl complexes containing open-chain crown ether for Mg 2+ and Ca 2+ probing

Six polypyridyl bridging ligands BL 1–6 containing open-chain crown ether, where BL 1–3 formed by the condensation of 4,5-diazafluoren-9-hydrazine with 1,7-bis-(4-formylphenyl)-1,4,7-trioxaheptane, 1,10-bis-(4-formylphenyl)-1,4,7,10-tetraoxadecane, and 1,13-bis-(4-formylphenyl)-1,4,7,10,13-pentaoxatridecane, respectively, BL 4–6 formed by the reaction of 9-(4-hydroxy)phenylimino-4,5-diazafluorene with diethylene glycol di- p-tosylate, triethylene glycol di- p-tosylate, and tetraethylene glycol di- p-tosylate, respectively, have been synthesized. Reaction of Ru(bpy) 2Cl 2·2H 2O with BL 1–6, respectively, afforded six bimetallic complexes [(bpy) 2RuBL 1–6Ru(bpy) 2] 4+ as PF 6 − salts. Cyclic voltammetry of these complexes is consistent with one Ru(II)-centered oxidation around 1.32 V and three ligand-centered reductions. These complexes show metal-to-ligand charge transfer absorption at 413–444 nm and emission at 570 nm. Binding behavior of complexes with alkali and alkaline-earth metal ions are investigated by UV–vis absorption, fluorescence, and cyclic voltammetry. Addition of alkali and alkaline-earth metal ions to the solution of [(bpy) 2RuBL 1–6Ru(bpy) 2](PF 6) 4 all result in a progressive quenching of fluorescence, a hyperchromic effect of UV–vis absorption, and a progressive cathodal shift of Ru(II)-centered E 1/2. Ru-BL 2 and Ru-BL 5 show the highest binding ability toward Mg 2+ among the five cations examined while Ru-BL 3 and Ru-BL 6 exhibit good selective recognition ability to Ca 2+.

Synthesis, Photophysical, and Electrochemical Properties of Ruthenium(II) Polypyridyl Complexes containing Open‐Chain Crown Ether

AbstractFour polypyridyl bridging ligands BL1−4 containing open‐chain crown ether, where BL1−3 formed by the condensation of 4,5‐diazafluoren‐9‐oxime with diethylene glycol di‐p‐tosylate, triethylene glycol di‐p‐tosylate, and tetraethylene glycol di‐p‐tosylate, respectively. BL4 formed by the reaction of 4‐(1,10‐phenanthrolin‐5‐ylimino)methylphenol with triethylene glycol di‐p‐tosylate, have been synthesized. Reaction of Ru(bpy)2Cl2·2H2O with BL, respectively, afforded four bimetallic complexes [(bpy)2RuBL1−4Ru(bpy)2]4+ as [PF6]− salts. Electrochemistry of these complexes is consistent with one RuII‐based oxidation and several ligand‐based reductions. These complexes show metal‐to‐ligand charge transfer absorption at 439‐452 nm and emission at 570‐597 nm.

Synthesis, photophysical, and electrochemical properties of three novel Ru(II) polypyridyl complexes containing dibenzo-18-crown-6

Three polypyridyl bridging ligands cis-di(4,5-diazafluoren-9-ylimino)dibenzo-18-crown-6 (BL1), trans-di(4,5-diazafluoren-9-ylimino)dibenzo-18-crown-6 (BL2), and 1,4,7,10,13,16-hexaoxacycloctadecyl[2,3:11,12]bis-dipyrido[3,2-a:2′3′-c]phenazine (BL3), and corresponding dinuclear Ru(II) complexes [(bpy)2RuBL1−3Ru(bpy)2](PF6)4 (1, 2, and 3) have been synthesized. Cyclic voltammetry of the complexes are consistent with one Ru(II)-centered oxidation and three ligand-centered reductions. Photophysical behaviors are investigated by UV–Vis absorption and fluorescence spectrometry. The three complexes show metal-to-ligand charge transfer absorption at 445–453nm and emission at 571–593nm.

Probing the Transition between the Localised (Class II) and Localised‐to‐Delocalised (Class II–III) Regimes by Using Intervalence Charge‐Transfer Solvatochromism in a Series of Mixed‐Valence Dinuclear Ruthenium Complexes

Intervalence charge-transfer (IVCT) solvatochromism studies on the diastereoisomeric forms of [{Ru(bpy)(2)}(2)(mu-BL)](5+) (bpy=2,2'-bipyridine; BL=a series of di-bidentate polypyridyl bridging ligands) reveal that the solvent dependencies of the IVCT transitions decrease as the "tail" of the bridging ligand is extended, and the extent of delocalisation increases. Utilising a classical theoretical approach for the analysis of the intervalence charge-transfer (IVCT) solvatochromism data, the subtle and systematic variation in the electronic properties of the bridging ligands can be correlated with the shift between the localised (class II) and localised-to-delocalised (class II-III) regimes. The investigation of the diastereoisomeric forms of two series of complexes incorporating analogous structurally rigid (fused) and nonrigid (unfused) bridging ligands demonstrates that the differences in the IVCT characteristics of the diastereoisomers of a given complex are accentuated in the latter case, due to a stereochemically induced redox asymmetry contribution. The marked dependence of the IVCT transitions on the stereochemical identity of the complexes provides a quantitative measure of the fundamental contributions of the reorganisational energy and redox asymmetry to the intramolecular electron-transfer barrier at the molecular level.

Binuclear ruthenium and osmium mixed-valence complexes containing fused and flexible polypyridyl bridging ligands

{Os(bpy) 2} 2+ and {Ru(CN) 4} 2− mononuclear and binuclear complexes with ligands 2,3-di-(2-pyridyl)quinoxaline (dpq) and dipyrido[2,3- a:3′,2′- c]phenazine (ppb) have been prepared. For the binuclear complexes a splitting in oxidation potentials is observed consistent with the formation of mixed-valence species with comproportionation constants ( K com) ranging from 2.5 × 10 4 to 1.8 × 10 6. The electronic absorption spectra of the mixed-valence species reveal IVCT transitions in the near infrared region. The absorption maximum for the IVCT band ranges from 5800 to 9980 cm −1 and the extinction coefficients from 80 to 6300 M −1 cm −1. In general the {Os(bpy) 2} 2+ complexes show larger K com values and more intense IVCT bands than the corresponding {Ru(CN) 4} 2− complexes.

Underlying Spin−Orbit Coupling Structure of Intervalence Charge Transfer Bands in Dinuclear Polypyridyl Complexes of Ruthenium and Osmium

The mixed-valence systems meso- and rac-[{M(bpy)2}2(mu-BL)]5+ {M = Ru, Os; BL = a series of polypyridyl bridging ligands such as 2,3-bis(2-pyridyl)benzoquinoxaline (dpb)} are characterized by multiple intervalence charge transfer (IVCT) and interconfigurational (IC) bands in the mid-infrared and near-infrared (NIR) regions. Differences in the relative energies of the IC transitions for the fully oxidized (+6) states of the osmium systems demonstrate that stereochemical effects lead to fundamental changes in the energy levels of the metal-based dpi orbitals, which are split by spin-orbit coupling and ligand-field asymmetry. An increase in the separation between the IC bands as BL is varied reflects the increase in the degree of electronic coupling through the series of ruthenium and osmium complexes. The increase in the IVCT bandwidths for the former is therefore attributed to the increase in the separation of the three underlying components of the bands. Stark effect measurements reveal small dipole moment changes accompanying IVCT excitation in support of the localized-to-delocalized or delocalized classification for the dinuclear ruthenium and osmium systems.

Synthetic Approaches to Polypyridyl Bridging Ligands with Proximal Multidentate Binding Sites

[reactions: see text] A series of 12 bridging ligands was prepared. These ligands include a central linker appended to two 1,8-naphthyrid-2-yl or two 1,10-phenanthrolin-2-yl units. The linkers include pyridazin-3,6-diyl, 1,8-naphthyrid-2,7-diyl, 2,2'-bipyrid-6,6'-diyl, 1,10-phenanthrolin-2,9-diyl, 1,2-di(2'-pyrid-6'-yl)ethyne, and 3,6-di(2'-pyrid-6'-yl)pyridazine. The ligands were synthesized from the diacetyl derivative of the central linker by a Friedländer condensation with either 2-aminonicotinaldehyde or 8-amino-7-quinolinecarbaldehyde. The precursor diacetyl derivatives were, in turn, prepared by pathways involving Stille and Sonogashira couplings. Examination of the electronic absorption spectra of the bridging ligands shows the strongest correlation to be between pairs of ligands having the same central linker. Complexation studies will follow.

Revealing the chromophoric composition of multichromophoric polypyridyl complexes of Re(I) and Os(II): a resonance Raman study

AbstractSeveral binuclear Re(I) and Re(I)Os(II) complexes with polypyridyl bridging ligands, 6,7‐dimethyl‐2,3‐di(2‐pyridyl)quinoxaline (dpqMe2) and [2,3‐a:3′,2′‐c]dipyrido‐6,7‐dimethylphenazine (ppbMe2), were synthesized and studied. The visible region of the electronic absorption spectrum is dominated by a single metal‐to‐ligand charge‐transfer band (ca 600 nm) and a dpqMe2‐ or ppbMe2‐based ligand‐centred band (ca 400 nm). The resonance Raman spectra of these complexes were recorded at several excitation wavelengths. Analysis of the resonance Raman spectra identified a number of strongly enhanced chromophore‐specific signatures with excitation wavelengths coincident with the main absorption bands, and weakly enhanced chromophore‐specific signatures at intermediate excitation wavelengths. Resonance Raman excitation profiles (RREPs) are presented for selected marker bands. Analysis of the chromophore‐specific signatures and the RREPs allowed a more complete assignment of the features in the electronic absorption spectra to be made. Copyright © 2002 John Wiley & Sons, Ltd.

Structure, spectroscopic and electrochemical properties of novel binuclear ruthenium(II) copper(I) complexes with polypyridyl bridging ligands †

Binuclear complexes of the type [(bpy)2Ru(BL)Cu(PPh3)2]3+, where bpy = 2,2′-bipyridine, BL = 2,3-di-2-pyridylpyrazine (dpp), 2,3-di-2-pyridylquinoxaline (dpq), or 6,7-dimethyl-2,3-di-2-pyridylquinoxaline (dpqMe2), were readily formed by the reaction of [Cu(PPh3)4]+ with mononuclear complexes [Ru(bpy)2(BL)]2+. The binuclear complexes are stable in CH2Cl2 solution at concentrations above 10–3 mol dm–3 having equilibrium constants for formation in the range 1000–2500 dm3 mol–1. Single crystal structures for [(bpy)2Ru(dpp)Cu(PPh3)2]3+ and [(bpy)2Ru(dpqMe2)Cu(PPh3)2]3+ show distortions of the bridging ligand in the form of twisting and splaying of the ring systems. Electrochemical and UV/Visible data suggest the {Cu(PPh3)2}+ moiety has little affect in stabilising the BL π* orbital. Resonance Raman spectra show the bichromophoric nature of the visible absorptions of the heteroleptic complexes; both bpy and BL ligand vibrations are enhanced depending on the excitation wavelength. Observation of a Ru–N vibration suggests that the dominant transition in the visible region is Ru(dπ)→BL(π*) CT.

Spectroelectrochemical studies of some ruthenium(II) complexes with polypyridyl bridging ligands

Ruthenium(II) bis(2,2″-pyridyl) complexes with bridging ligands: 6,7-dichloro-2,3-di(2-pyridyl)quinoxaline; 2,3-di(2-pyridyl)-quinoxaline; 5-methyl-2,3-di(2-pyridyl) quinoxaline; 6,7-dibenzo-2,3-di(2-pyridyl)quinoxaline have been prepared. The electrochemical and spectroscopic properties of these complexes are reported. The resonance Raman spectroelectrochemical results indicate the presence of oxidation state sensitive marker bands in the resonance Raman spectra of the oxidized complexes. The spectroscopic data for the reduced complexes is similar for all four species. The resonance Raman data for the reduced species are dominated by 2,2″-bipyridyl vibrations.

Spectroelectrochemical studies of ruthenium(II) diimine complexes with polypyridyl bridging ligands

Ruthenium(II) complexes with polypyridyl bridging ligands 2,3-di(2-pyridyl)pyrazine (dpp) and 6,7-dimethyl-2,3-di(2-pyridyl)-quinoxaline (dpqm) have been prepared. The electronic and resonance Raman spectra of the parent complexes and their reduced and oxidized products have been measured. These results indicate that for both complexes the first oxidation is metal based and the first reduction bridging ligand based. Raman marker bands for the metal oxidation have been identified. The resonance Raman spectra of the reduced species suggest electron localization of the LUMO to be spread across the pyridine and pyrazine/quinoxaline sections of the bridging ligands.

Spectroscopic, electrochemical, and spectroelectrochemical investigations of mixed-metal osmium(II)/ruthenium(II) bimetallic complexes incorporating polypyridyl bridging ligands

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSpectroscopic, electrochemical, and spectroelectrochemical investigations of mixed-metal osmium(II)/ruthenium(II) bimetallic complexes incorporating polypyridyl bridging ligandsMark M. Richter and Karen J. BrewerCite this: Inorg. Chem. 1992, 31, 9, 1594–1598Publication Date (Print):April 1, 1992Publication History Published online1 May 2002Published inissue 1 April 1992https://doi.org/10.1021/ic00035a014RIGHTS & PERMISSIONSArticle Views221Altmetric-Citations46LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (602 KB) Get e-Alerts Get e-Alerts

Synthesis and characterization of osmium(II) complexes incorporating polypyridyl bridging ligands

A series of osmium(II) compounds have been prepared which contain the polypyridyl bridging ligands 2,3-bis(2′-pyridyl)pyrazine (dpp), 2,3-bis(2′-pyridyl)quinoxaline (dpq) and 2,3-bis(2′-pyridyl)benzoquinoxaline (dpb). The compounds [Os(bpy) 2(dpp)](PF 6) 2, [Os(bpy) 2(dpq)](PF 6) 2 and [Os(bpy) 2(dpb)](PF 6) 2 (bpy=2,2′-bipyridine) have been synthesized and their electrochemical and spectroscopic properties have been studied and are reported herein. The complexes show absorbances throughout the visible region of the spectrum. The potential of the first electrochemical reduction as well as the energy of the lowest energy metal to ligand charge transfer excited state (MLCT) are found to be dependent upon the nature of the bridging polypyridyl ligand. This combined with the fact that the bridging ligands are more easily reduced than bipyridine support the assignment of the lowest unoccupied molecular orbital (LUMO) as arising from a bridging ligand based π * orbital.

ChemInform Abstract: Synthesis and Characterization of a Series of Novel Rhodium and Iridium Complexes Containing Polypyridyl Bridging Ligands: Potential Uses in the Development of Multimetal Catalysts for Carbon Dioxide Reduction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis and characterization of a series of novel rhodium and iridium complexes containing polypyridyl bridging ligands: potential uses in the development of multimetal catalysts for carbon dioxide reduction

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and characterization of a series of novel rhodium and iridium complexes containing polypyridyl bridging ligands: potential uses in the development of multimetal catalysts for carbon dioxide reductionSeth C. Rasmussen, Mark M. Richter, Eugene Yi, Helen Place, and Karen J. BrewerCite this: Inorg. Chem. 1990, 29, 20, 3926–3932Publication Date (Print):October 1, 1990Publication History Published online1 May 2002Published inissue 1 October 1990https://doi.org/10.1021/ic00345a005RIGHTS & PERMISSIONSArticle Views1003Altmetric-Citations112LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (876 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts