59 research outputs found
Hybrid inorganic-organic, organic charge transfer, and radical based compounds with chalcofulvalene donors and organic acceptors
The primary focus of this dissertation is the electrochemical preparation of radical
cation salts utilizing the donor o-4,4â-dimethyltetrathiafulvalene (o-Me2TTF) and
spherical, tetrahedral, octahedral, bimetallic, cyanometallate, and polyoxometallate
anions. Other donors, such as tetramethyl(tetraselenafulvalene) (TMTSF),
tetramethyl(tetrathiafulvalene) (TMTTF), bis(ethylenedithio)tetrathiafulvalene (BEDTTTF
or ET), and bis(propylenedithio)tetrathiafulvalene (BPDT-TTF or PT) also found
use in the preparation of salts in the course of this study. X-ray structural
characterization of these salts revealed stacking between donor molecules containing
significant SâąâąâąS interactions in the solid state. Various salts were subjected to either
conductivity or molecular magnetism measurements in order to determine the level of
itinerant electron density and magnetic contribution from paramagnetic charge
compensating anions. In order to expand the library of TTF-containing hybrid materials
prepared through metathesis, salts of other tetrathiafulvalenium radicals have also been
prepared and characterized crystallographically and by select spectroscopic methods. In an effort to gain further information on formation of organic charge transfer
complexes, TTF was combined with nitrofluorenone family of acceptors as well as the
organocyanide acceptors HAT-(CN)6 (HAT-(CN)6 = 1,4,5,8,9,12-hexaazatriphenylenehexacarbonitrile)
and TCNB (TCNB = 1,2,4,5-tetracyanobenzene). The complexes were
characterized using X-ray crystallography, infrared spectroscopy, and molecular
magnetism. All of these techniques showed that all compounds underwent little to no
charge transfer.
Commencing in 2003, the combined work of Dunbar and Omary revealed that
systems combining inorganic donors with chelating, sulfur-based ligands and organic
acceptors could have their spectroscopic response tuned to display low-energy charge
transfer bands extending into the near-IR making them suitable candidates as
photosensitizing dyes for semiconductors. In keeping with this idea, new layered charge
transfer compounds combining the nitrofluorenone family of acceptors and the inorganic
donor Pt(dbbpy)(tdt) (tdt = 3,4-toluenedithiolate) were prepared. The resulting
complexes were characterized utilizing X-ray crystallography as well as both
spectroscopic and electrochemical methods. Similar analyses were also conducted on
various platinum/terpyridine salts and illustrated a level of spectroscopic tunability to that
observed for the supramolcular systems composed of inorganic donors and organic
acceptors
Hybrid Material Based on the Lindquist Polyoxometalate [W6O19]2â and the organosulfur donor o-Me2TTF: A Combined Structural and Spectroscopic Study
International audienceThe synthesis, crystal structure and spectroscopic properties of the hybrid radical cation salt containing oxidized o-3,4-dimethyltetrathiafulvalene (o-Me2TTF) and the Lindquist polyoxometalate anion [W6O19]2â are reported. The title salt represents the first time a Lindquist polyoxometalate has been utilized as the counter anion with this unsymmetrical member of the TTF family of derivatives. The salt crystallizes in the triclinic space group P1ÂŻ with a = 7.6211(7) Ă
, b = 9.5231(9) Ă
, c = 12.2148(11) Ă
, α = 105.5870(10)°, ÎČ = 106.8340(10)° and Îł = 95.6950(10)°. Resolution of the solid state structure revealed that the o-Me2TTF radical cations aggregate as isolated face-to-face dimers with intradimer interactions between neighboring sulfur atoms at distances <3.6 Ă
. Hydrogen bonding was also observed between hydrogen atoms bound to sp 2-hybridized carbon atoms of o-Me2TTF and bridging oxygen atoms of [W6O19]2â. Single crystal IR and Raman spectra were also collected and provide further evidence that the o-Me2TTF donors have been oxidized to their corresponding radical cationic states
Electron-molecular vibration coupling in (DMtTTF)Br and (o-DMTTF)2[W6O19] salts studied by vibrational spectroscopy
International audienceA novel 1:1 salt encompassing radical cations of DMtTTF (DMtTTF = dimethyltrimethylene-tetrathiafulvalene) and the Brâanion has been synthesized. Close inspection of the salt's solid state structure revealed the presence of quasi-isolated dimers containing DMtTTF radical cations, a specific arrangement whereby the microscopic parameters of DMtTTFradical dot+ might be studied. Analysis of the corresponding single crystal IR and Raman spectra of (DMtTTF)Br allowed us to study the material's electronic and vibrational structure and to evaluate the electron-molecular coupling constants via the isolated dimer model. Additionally, using previously published IR data, analogous calculations were performed on the salt (o-DMTTF)2[W6O19] (o-DMTTF = o-3,4-dimethyltetrathiafulvalene), which also contains well isolated dimers of o-DMTTF radical cations. These calculations revealed that the coupling constants for the unsymmetrical donors studied herein are comparable to those for symmetric TTF derivatives
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New emissive mononuclear copper (I) complex: Structural and photophysical characterization focusing on solvatochromism, rigidochromism and oxygen sensing in mesoporous solid matrix
Magnetic ordering in self-assembled materials consisting of cerium(III) ions and the radical forms of 2,5-TCNQX 2 (X=Cl, Br)
Ribbon-like coordination polymers composed of CeIII ions and TCNQX2 (TCNQ=tetracyanoquinodimethane; X=Cl, Br), but not TCNQ radicals, show unexpected magnetic ordering (see picture; Ce green). This behavior reveals remarkable subtlety for magnetic properties of lanthanideâorganic materials
Copper (I) SNS Pincer Complexes: Impact of Ligand Design and Solvent Coordination on Conformer Interconversion from Spectroscopic and Computational Studies
The syntheses and detailed characterizations (X-ray crystallography, NMR spectroscopy, cyclic voltammetry, infrared spectroscopy, electrospray mass spectrometry, and elemental analyses) of two new Cu(I) pincer complexes are reported. The pincer ligand coordinates through one nitrogen and two sulfur donor atoms and is based on bis-imidazole or bis-triazole precursors. These tridentate SNS ligands incorporate pyridine and thione-substituted imidazole or triazole functionalities with connecting methylene units that provide flexibility to the ligand backbone and enable high bite-angle binding. Variable temperature 1H NMR analysis of these complexes and of a similar zinc(II) SNS system shows that all are fluxional in solution and permits the determination of ÎGexp⥠and ÎSexpâĄ. DFT calculations are used to model the fluxionality of these complexes and indicate that a coordinating solvent molecule can promote hemilability of the SNS ligand by lowering the energy barrier involved in the partial rotation of the methylene units
Cupriphication of gold to sensitize d10âd10 metalâmetal bonds and near-unity phosphorescence quantum yields
Outer-shell s0/p0 orbital mixing with d10 orbitals and symmetry reductionuponcupriphicationofcyclic trinucleartrigonal-planargold(I) complexes are found to sensitize ground-state Cu(I)âAu(I) covalent bonds and near-unity phosphorescence quantum yields. Heterobimetallic Au4Cu2 {[Au4(ÎŒ-C2,N3-EtIm)4Cu2(ÎŒ-3,5-(CF3)2Pz)2], (4a)}, Au2Cu {[Au2(ÎŒ-C2,N3-BzIm)2Cu(ÎŒ-3,5-(CF3)2Pz)], (1) and [Au2(ÎŒ-C2, N3-MeIm)2Cu(ÎŒ-3,5-(CF3)2Pz)], (3a)}, AuCu2 {[Au(ÎŒ-C2,N3-MeIm)Cu2(ÎŒ3,5-(CF3)2Pz)2], (3b) and [Au(ÎŒ-C2,N3-EtIm)Cu2(ÎŒ-3,5-(CF3)2Pz)2], (4b)} and stacked Au3/Cu3 {[Au(ÎŒ-C2,N3-BzIm)]3[Cu(ÎŒ-3,5-(CF3)2Pz)]3, (2)} formuponreactingAu3 {[Au(ÎŒ-C2,N3-(N-R)Im)]3 ((N-R)Im = imidazolate; R =benzyl/methyl/ethyl =BzIm/MeIm/EtIm)} with Cu3 {[Cu(ÎŒ-3,5(CF3)2Pz)]3 (3,5-(CF3)2Pz = 3,5-bis(trifluoromethyl)pyrazolate)}. The crystal structures of 1 and 3a reveal stair-step infinite chains whereby adjacent dimer-of-trimer units are noncovalently packed via twoAu(I)âŻCu(I)metallophilicinteractions,whereas 4a exhibitsa hexanuclear cluster structure wherein two monomer-of-trimer units are linked by a genuine d10âd10 polar-covalent bond with ligandunassisted Cu(I)âAu(I) distances of 2.8750(8) Ă
eachâthe shortest such an intermolecular distance ever reported between any two d10 centers so as to deem it a âmetalâmetal bondâ vis-Ă -vis âmetallophilic interaction.â Density-functional calculations estimate 35â 43kcal/molbindingenergy,akintotypicalMâMsingle-bondenergies. Congruently, FTIR spectra of4a showmultiple far-IR bands within 65â 200 cmâ1, assignable to vCu-Au as validated by both the HarveyâGray method of crystallographic-distance-to-force-constant correlation and dispersive density functional theory computations. Notably, the heterobimetallic complexes herein exhibit photophysical properties that are favorable to those for their homometallic congeners, due to threefold-to-twofold symmetry reduction, resulting in cuprophilicsensitizationinextinctioncoefficientandsolid-state photoluminescence quantum yields approaching unity (ΊPL = 0.90â0.97 vs. 0â0.83 for Au3 and Cu3 precursors), which bodes well for potential future utilization in inorganic and/or organic LED applications
Synthesis, Characterization, and Computational Study of Three-Coordinate SNS Copper(I) Complexes Based on Bis-Thione Ligand Precursors
A series of tridentate pincer ligands, each possessing two sulfur and one nitrogen donor (SNS), based on bis-imidazolyl or bis-triazolyl salts were metallated with CuCl2 to give new tridentate SNS pincer copper(I) complexes [(SNS)Cu]+. These orange complexes exhibit a three-coordinate pseudo-trigonal-planar geometry in copper. During the formation of these copper(I) complexes, disproportionation is observed as the copper(II) salt precursor is converted into the Cu(I) [(SNS)Cu]+ cation and the [CuCl4]2â counteranion. The [(SNS)Cu]+ complexes were characterized with single crystal X-ray diffraction, electrospray mass spectrometry, EPR spectroscopy, attenuated total reflectance infrared spectroscopy, UVâVis spectroscopy, cyclic voltammetry, and elemental analysis. The EPR spectra are consistent with anisotropic Cu(II) signals with four hyperfine splittings in the lower-field region (g||) and g values consistent with the presence of the tetrachlorocuprate. Various electronic transitions are apparent in the UVâVis spectra of the complexes and originate in the copper-containing cations and anions. Density functional calculations support the nature of the SNS binding, allowing assignment of a number of features present in the UVâVis and IR spectra and cyclic voltammograms of these complexes
Catalytic intramolecular hydroamination of aminoallenes using titanium complexes of chiral, tridentate, dianionic imine-diol ligands
Alkylation of D- or L-phenylalanine or valine alkyl esters was carried out using methyl or phenyl Grignard reagents. Subsequent condensation with salicylaldehyde, 3,5-di-tert-butylsalicylaldehyde, or 5-fluorosalicylaldehyde formed tridentate, X_2L type, Schiff base ligands. Chiral shift NMR confirmed retention of stereochemistry during synthesis. X-ray crystal structures of four of the ligands show either inter- or intramolecular hydrogen bonding interactions. The ligands coordinate to the titanium reagents Ti(NMe_2)_4 or TiCl(NMe_2)_3 by protonolysis and displacement of two equivalents of HNMe_2. The crystal structure of one example of Ti(X_2L)Cl(NMe_2) was determined and the complex has a distorted square pyramidal geometry with an axial NMe_2 ligand. The bis-dimethylamide complexes are active catalysts for the ring closing hydroamination of di- and trisubstituted aminoallenes. The reaction of hepta-4,5-dienylamine at 135 °C with 5 mol% catalyst gives a mixture of 6-ethyl-2,3,4,5-tetrahydropyridine (40â72%) and both Z- and E-2-propenyl-pyrrolidine (25â52%). The ring closing reaction of 6-methyl-hepta-4,5-dienylamine at 135 °C with 5 mol% catalyst gives exclusively 2-(2-methyl-propenyl)-pyrrolidine. The pyrrolidine products are obtained with enantiomeric excesses up to 17%
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