PUMA publications for /user/b_schwederski/azobipyridinehttps://puma.ub.uni-stuttgart.de/user/b_schwederski/azobipyridinePUMA RSS feed for /user/b_schwederski/azobipyridine2024-03-28T19:45:40+01:00Mono- and binuclear molybdenum carbonyl complexes with charge-transfer absorptions in the near IRhttps://puma.ub.uni-stuttgart.de/bibtex/217afc90e24cc02a5d1ecba7b6da4deb0/b_schwederskib_schwederski2019-07-15T13:41:23+02:00IR IR;bipyrimidine IR;charge IR;molybdenum absorption absorption;pyridyltetrazine azobipyridine carbonyl complex diimine;diimine molybdenum transfer <span data-person-type="author" class="authorEditorList "><span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Wolfgang Kaim" itemprop="url" href="/person/19299a5f60440d6d8993d5c2562bdd552/author/0"><span itemprop="name">W. Kaim</span></a></span>, </span><span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Sylvia Ernst" itemprop="url" href="/person/19299a5f60440d6d8993d5c2562bdd552/author/1"><span itemprop="name">S. Ernst</span></a></span>, </span> and <span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Stephan. Kohlmann" itemprop="url" href="/person/19299a5f60440d6d8993d5c2562bdd552/author/2"><span itemprop="name">S. Kohlmann</span></a></span></span>. </span><span class="additional-entrytype-information"><span itemtype="http://schema.org/PublicationIssue" itemscope="itemscope" itemprop="isPartOf"><em><span itemprop="journal">Polyhedron</span>, </em> <em><span itemtype="http://schema.org/PublicationVolume" itemscope="itemscope" itemprop="isPartOf"><span itemprop="volumeNumber">5 </span></span>(<span itemprop="issueNumber">1-2</span>):
<span itemprop="pagination">445--449</span></em> </span>(<em><span>1986<meta content="1986" itemprop="datePublished"/></span></em>)</span>Mon Jul 15 13:41:23 CEST 2019Polyhedron1-2445--449Mono- and binuclear molybdenum carbonyl complexes with charge-transfer absorptions in the near IR51986IR IR;bipyrimidine IR;charge IR;molybdenum absorption absorption;pyridyltetrazine azobipyridine carbonyl complex diimine;diimine molybdenum transfer Mo(PBu3)2(CO)2(bpm) (bpm = 4,4'-bipyrimidine), Mo(CO)4L (L = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, azo-2,2'-bipyridine), and Mo2(CO)8L with very long wavelength change-transfer absorptions (\textgreek{l} = 700-1000 nm) were obtained via lowering of the complex LUMO, viz. by using strongly \textgreek{p}-accepting \textgreek{a}-diimine ligands, and via raising of the metal highest occupied MO, viz. by using the electron-rich metal fragment Mo(PBu3)2(CO)2. The electronic structures of these compds. were studied by electron and IR spectroscopy, by cyclic voltammetry and by ESR of the anion radicals. [on SciFinder(R)]Semireduced bridging ligands containing N-N multiple bond coordination sites. ESR study of binuclear Group 6 metal carbonyl complexeshttps://puma.ub.uni-stuttgart.de/bibtex/26ad1a8ae43588b97eaaf9c190e5536b6/b_schwederskib_schwederski2019-07-15T13:41:23+02:00ESR ESR;ENDOR ESR;tetrazine VIB azobipyridine azopyridine binuclear carbonyl complex complex;ESR complex;pyridyltetrazine molybdenum <span data-person-type="author" class="authorEditorList "><span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Wolfgang Kaim" itemprop="url" href="/person/18f4f2bb44536807f1df27fd633b9cf33/author/0"><span itemprop="name">W. Kaim</span></a></span>, </span> and <span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Stephan. Kohlmann" itemprop="url" href="/person/18f4f2bb44536807f1df27fd633b9cf33/author/1"><span itemprop="name">S. Kohlmann</span></a></span></span>. </span><span class="additional-entrytype-information"><span itemtype="http://schema.org/PublicationIssue" itemscope="itemscope" itemprop="isPartOf"><em><span itemprop="journal">Inorganic Chemistry</span>, </em> <em><span itemtype="http://schema.org/PublicationVolume" itemscope="itemscope" itemprop="isPartOf"><span itemprop="volumeNumber">25 </span></span>(<span itemprop="issueNumber">19</span>):
<span itemprop="pagination">3442--3448</span></em> </span>(<em><span>1986<meta content="1986" itemprop="datePublished"/></span></em>)</span>Mon Jul 15 13:41:23 CEST 2019Inorganic Chemistry193442--3448Semireduced bridging ligands containing N-N multiple bond coordination sites. ESR study of binuclear Group 6 metal carbonyl complexes251986ESR ESR;ENDOR ESR;tetrazine VIB azobipyridine azopyridine binuclear carbonyl complex complex;ESR complex;pyridyltetrazine molybdenum Centrosym. binuclear metal carbonyl complexes of anion radical ligands contg. the azo group -N:N- were studied by using ESR. The ligands employed were 1,2,4,5-tetrazine (tz), 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz), and azo-2,2'-bipyridine (abpy). The radical complexes studied were: (\textgreek{m}-(N1,N4)-tz.-)[M(CO)5]2 (M = Mo, W); (\textgreek{m}-bptz.-)[M(CO)4]2, and (\textgreek{m}-abpy).-)[M(CO)4]2 (M = Cr, Mo, W). The ESR spectra of abpy species are line rich and insufficiently resolved so that ENDOR spectroscopy was used for (\textgreek{m}-abpy.-)[Mo(CO)4]2. In contrast, the tetrazine complexes exhibit a rather simple ESR hyperfine structure because of spin localization at the 4 N centers in the tetrazine ring. The obsd. response of the hyperfine structure on metal coordination is well reproduced by HMO-McLachlan perturbation calcns. of the spin distribution. Double coordination of equiv. metal fragments and spin localization at the tetrazine N centers create exceptionally favorable conditions to detect metal isotope coupling; a survey of these and several related anion radical complexes shows that the small metal isotope splittings are caused by \textgreek{s}/\textgreek{p} spin polarization originating from the coordinating N \textgreek{p} center. [on SciFinder(R)]EPR evidence for related electronic structures of a-diimine complexes with bis(bipyridine)ruthenium(2+) (Ru(bpy)22+) and rhenium carbonyl(Re(CO)3)(halide) fragmentshttps://puma.ub.uni-stuttgart.de/bibtex/29bf064a519c0edaeaeedcb83efb1deb4/b_schwederskib_schwederski2019-07-15T13:41:23+02:00EPR ESR;electronic ESR;rhenium azobipyridine carbonyl diimine;photocatalyst diimine;pyridine halo rhenium structure <span data-person-type="author" class="authorEditorList "><span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="W. Kaim" itemprop="url" href="/person/13c7f8ff30e6c2078df14fdfd51898b7e/author/0"><span itemprop="name">W. Kaim</span></a></span>, </span> and <span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="S. Kohlmann" itemprop="url" href="/person/13c7f8ff30e6c2078df14fdfd51898b7e/author/1"><span itemprop="name">S. Kohlmann</span></a></span></span>. </span><span class="additional-entrytype-information"><span itemtype="http://schema.org/PublicationIssue" itemscope="itemscope" itemprop="isPartOf"><em><span itemprop="journal">Chemical Physics Letters</span>, </em> <em><span itemtype="http://schema.org/PublicationVolume" itemscope="itemscope" itemprop="isPartOf"><span itemprop="volumeNumber">139 </span></span>(<span itemprop="issueNumber">3-4</span>):
<span itemprop="pagination">365--369</span></em> </span>(<em><span>1987<meta content="1987" itemprop="datePublished"/></span></em>)</span>Mon Jul 15 13:41:23 CEST 2019Chemical Physics Letters3-4365--369EPR evidence for related electronic structures of \textgreek{a}-diimine complexes with bis(bipyridine)ruthenium(2+) ([Ru(bpy)2]2+) and rhenium carbonyl(Re(CO)3)(halide) fragments1391987EPR ESR;electronic ESR;rhenium azobipyridine carbonyl diimine;photocatalyst diimine;pyridine halo rhenium structure Low-lying unoccupied orbitals of the fragments Re(CO)3X, X = Cl and Br, were inferred from EPR spectroscopy of mono- and dinuclear complexes with the singly reduced \textgreek{a}-diimine ligands 2,2'-dipyridine and azo-2,2'-bipyridine. The magnitudes of 185,187Re and unresolved halide hyperfine splitting could be established in spite of the poor spectra resoln. The spectroscopic similarities between \textgreek{a}-diimine complexes of Re(CO)3X and [Ru(bpy)2]2+ fragments are discussed with respect to their related electronic structures and photocatalytic reactivities. [on SciFinder(R)]What determines the comproportionation constant in molecule-bridged mixed-valence complexes? Evidence for the crucial role of the ligand LUMO in four ruthenium(II)ruthenium(III) dimershttps://puma.ub.uni-stuttgart.de/bibtex/299b300f3415ae63df8e73244441279dd/b_schwederskib_schwederski2019-07-15T13:41:23+02:00azobipyridine bipyridine complex complex;LUMO complex;electron complex;pyridylpyrazine comproportionation;comproportionation comproportionation;pyridyltetrazine comproportionation;sym comproportionation;voltammetry density dinuclear heterocycle mixed nitrogen ruthenium valent voltammetry <span data-person-type="author" class="authorEditorList "><span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Sylvia Ernst" itemprop="url" href="/person/11c9f5bb409e2cf5c26cf63b9bab8aab6/author/0"><span itemprop="name">S. Ernst</span></a></span>, </span><span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Volker Kasack" itemprop="url" href="/person/11c9f5bb409e2cf5c26cf63b9bab8aab6/author/1"><span itemprop="name">V. Kasack</span></a></span>, </span> and <span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Wolfgang. Kaim" itemprop="url" href="/person/11c9f5bb409e2cf5c26cf63b9bab8aab6/author/2"><span itemprop="name">W. Kaim</span></a></span></span>. </span><span class="additional-entrytype-information"><span itemtype="http://schema.org/PublicationIssue" itemscope="itemscope" itemprop="isPartOf"><em><span itemprop="journal">Inorganic Chemistry</span>, </em> <em><span itemtype="http://schema.org/PublicationVolume" itemscope="itemscope" itemprop="isPartOf"><span itemprop="volumeNumber">27 </span></span>(<span itemprop="issueNumber">7</span>):
<span itemprop="pagination">1146--1148</span></em> </span>(<em><span>1988<meta content="1988" itemprop="datePublished"/></span></em>)</span>Mon Jul 15 13:41:23 CEST 2019Inorganic Chemistry71146--1148What determines the comproportionation constant in molecule-bridged mixed-valence complexes? Evidence for the crucial role of the ligand LUMO in four ruthenium(II)ruthenium(III) dimers271988azobipyridine bipyridine complex complex;LUMO complex;electron complex;pyridylpyrazine comproportionation;comproportionation comproportionation;pyridyltetrazine comproportionation;sym comproportionation;voltammetry density dinuclear heterocycle mixed nitrogen ruthenium valent voltammetry Electrochem. data of 4 bis chelate bridged complexes {[Ru(bpy)2]2(μ, η4-L)}n+ (bpy = 2,2'-bipyridine, L = sym. N heterocycle such as 3,6-di-2-pyridyl-1,2,4,5-tetrazine, 2,5-di-2-pyridylpyrazine, 2,2'-bipyrimidine or azo-2,2'-bipyridine) show conclusively that the electron d. at the coordination centers in the LUMO of the bridging \textgreek{p} ligand dets. the comproportionation const. of the RuIIRuIII mixed-valence state (n = 5). Neither the no. of mediating \textgreek{p} centers nor the distance or the orientation of the 2 metal centers plays a significant role. The presence of 2 equiv chiral metal centers in these complexes leads to formation of meso and DL diastereomers, as shown for one example by 1H NMR. [on SciFinder(R)]Four bridging bis chelate ligands with very low lying p* orbitals. MO perturbation calculations, electrochemistry, and spectroscopy of mononuclear and binuclear group 6 metal tetracarbonyl complexeshttps://puma.ub.uni-stuttgart.de/bibtex/232ee25b910134ec22e13a1b299291934/b_schwederskib_schwederski2019-07-15T13:41:23+02:00Group MO VIB azobipyridine bipyrimidine bischelant carbonyl;Group carbonyl;MO carbonyl;electronic carbonyl;energy electrochem electrochem;bipyrimidine electrochem;electrochem electrochem;pyridyltetrazine level pyridylpyrazine pyridyltetrazine;pyridylpyrazine transition <span data-person-type="author" class="authorEditorList "><span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Wolfgang Kaim" itemprop="url" href="/person/16939cad18951d07991ceb8002a8240c6/author/0"><span itemprop="name">W. Kaim</span></a></span>, </span> and <span><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Stephan. Kohlmann" itemprop="url" href="/person/16939cad18951d07991ceb8002a8240c6/author/1"><span itemprop="name">S. Kohlmann</span></a></span></span>. </span><span class="additional-entrytype-information"><span itemtype="http://schema.org/PublicationIssue" itemscope="itemscope" itemprop="isPartOf"><em><span itemprop="journal">Inorganic Chemistry</span>, </em> <em><span itemtype="http://schema.org/PublicationVolume" itemscope="itemscope" itemprop="isPartOf"><span itemprop="volumeNumber">26 </span></span>(<span itemprop="issueNumber">1</span>):
<span itemprop="pagination">68--77</span></em> </span>(<em><span>1987<meta content="1987" itemprop="datePublished"/></span></em>)</span>Mon Jul 15 13:41:23 CEST 2019Inorganic Chemistry168--77Four bridging bis chelate ligands with very low lying \textgreek{p}* orbitals. MO perturbation calculations, electrochemistry, and spectroscopy of mononuclear and binuclear group 6 metal tetracarbonyl complexes261987Group MO VIB azobipyridine bipyrimidine bischelant carbonyl;Group carbonyl;MO carbonyl;electronic carbonyl;energy electrochem electrochem;bipyrimidine electrochem;electrochem electrochem;pyridyltetrazine level pyridylpyrazine pyridyltetrazine;pyridylpyrazine transition Coordination characteristics of the 4 bridging, \textgreek{p}-delocalized bis chelate ligands 2,2'-bipyrimidine (bpym), 2,5-bis(2-pyridyl)pyrazine (bppz), 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz), and azo-2,2'-bipyridine (abpy) were evaluated with use of \textgreek{p} MO perturbation calcns. and were studied exptl. by example of mononuclear and binuclear complexes with the fragments M(CO)4 (M = Cr, Mo, W). The substantial stabilization of the \textgreek{p}* (LUMO) levels in the order bpym, bppz, bptz, abpy strongly facilitates redn. of the complexes and causes shifts of the intense metal-to-ligand charge-transfer (LMCT) absorption bands out into the near-IR region. Despite a notable activation barrier for the formation of binuclear abpy complexes with 6-coordinate metals, (abpy)[Mo(CO)4]2 was prepd. and it exhibits most remarkable spectral properties such as an intense yet rather narrow and solvent-insensitive MLCT absorption band at 11,000 cm-1, another detectable absorption max. {\textgreater}30,000 cm-1, a redn. potential close to that of the ref. electrode, SCE, and closely spaced yet well-resolved CO stretching frequencies in the IR spectrum. All these spectral results can be correlated to \textgreek{p} MO calcn. data, which strongly suggest the use of bptz and abpy for studies concerned with ligand-mediated electronic interactions between metal centers. A particular asset of binuclear abpy complexes is the unusually short metal-metal distance caused by their coordination-induced S-frame conformation. [on SciFinder(R)]