Synthesis and photophysical properties of five-membered ring π-conjugated materials based on bisthiazol-2-yl-amine and their metal complexation studies

Poly(5,5′-(2-hexyldecyl)-bisthiazol-2-yl-amine) (PBTA) is prepared by nickel(0) mediated Yamamoto-type coupling. The photoluminescence (PL) spectrum of PBTA in THF solution displays pure blue emission with a peak centered at 444 nm without any shoulder peaks and the HOMO and LUMO values for PBTA are estimated to be 5.11  and 2.90 eV, respectively. In addition, we have synthesized a novel bisthiazol-2-yl-amine (BTA)-cored donor-acceptor (D-A) chromophore system, namely 5-(4-(diphenylamino)phenyl)-N-(5-(4-(diphenylamino)phenyl)thiazol-2-yl)-N-octylthiazol-2-amine (2-TPA-BTA) in which the electron-donating (D) moiety is triphenylamine group and the electron-withdrawing (A) unit is thiazole group. Furthermore, in this report, we present the complexation studies of both the BTA and 2-TPA-BTA chromophores with Cu(II) and Pd(II), respectively. The crystal structures are established by single-crystal X-ray diffraction analysis. These studies not only provide the general photophysical principles of the materials based on BTA moiety but also encourage progress toward realizing the full potential of its hybrid metal-organic frameworks.     

Novel π-conjugated molecules based on diimidazopyridine: Significantly improved the photophysical,thermal and electrochemical properties bearing different aryl substituents

A series of π-conjugated molecules based on diimidazolepyridine derivatives were designed, synthesized by Suzuki coupling reaction and cyclization reaction and characterized. Diimidazolepyridine motif as the main structure could improve the thermal stability and optical property of the materials. All of the target compounds exhibited good thermal stabilities with T_d values in the range of 416–490?°C. These compounds showed steady blue light emissions in the range of 424–478?nm and high quantum yields (0.33–0.69) in solution. Especially, compound 4f achieved appropriate energy gap (E_g?=?2.69?eV) and high fluorescence quantum yields (Φ_f?=?0.69) because of introducing electron-donating group, such energy gap was helpful to electronic transfer and transport. The materials have great potential for good electronic-transmission materials in OLEDs.     

The effects of surface ligands and counter cations on the stability of anionic thiolated M12Ag32 （M=Au,Ag） nanoclusters

The stabilities of [M12Ag32（SR）30]4- （M = Ag, Au and SR = SPhF2, SPhCF3, SPhF） clusters having the same structure but different surface ligands or counter cations were systematically studied. It was clearly revealed that a subtle structural change in the surface ligands or counter cations could significantly alter the overall stability of [M12Ag32（SR）30]4 although they all had an electronic structure of 18-electron superatom shell closure. SPhF2 was found as a better surface ligand than SPhCF3 or SPhF to stabilize [M12Ag32（SR）30]4-. And the use of more bulky [（PPhj）2N]＋ as the counter cations was revealed to be more deleterious to the overall stability of [M12Ag32（SR）30]4- clusters than PPh4＋. [Au12Ag32（SR）30]4- was much more stable than [Ag44（SR）30]4 with the same surface ligands and counter cations. An exceptional stability was observed on （PPh4）4[Au12Ag32（SPhF2）30] which was stable in DMF for more than 8 days in air at 80 ℃. More research efforts are still needed to deeply understand why a small structural change could result in a significant change in the stability of noble metal nanoclusters.     

Expanding family of π-conjugated trinuclear dithiolenes: the cases of group 8 (Ru(II)) and 10 (Ni(II) and Pt(II)) metals

New π-conjugated trinuclear dithiolenes with group 8 (6, Ru(II)) and 10 (7 and 8, Ni(II) and Pt(II)) metals were synthesized. Compounds 6 and 7 exhibited intense electronic communication through the phenylene bridge among the three dithiolene moieties during oxidation of the metalladithiolene rings, which has not been confirmed in the analogous family of group 9 metals, 1-5. Compound 8 exhibited an intense absorption band across the visible and near-IR regions, which was assigned as a charge transfer to the diimine and was red-shifted and broadened compared to the corresponding band of the mononuclear complex.     

Molecular complexes of cyclophanes,XVIII: Spectroscopic and thermodynamic studies on the charge-transfer complexes between 4-([2.2]paracyclophanoyl)amines and π-acceptors

The charge-transfer (CT) complexes of several substituted 4-([2.2]paracyclophanoyl)amines as donors with tetracyanoethylene (TCNE) and 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) as -acceptors have been studied spectrophotometrically. The role of the molecular structure of the donors on their Lewis basicities, the site and type of CT interactions are discussed. The thermodynamic properties of some CT complexes as well as the solvent effect on the CT complexation are reported.

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Molekulare Komplexe von Cyclophanenen, 18. Mitt.: Spektroskopische und thermodynamische Untersuchungen der Charge-Transfer-Komplexe von 4-([2.2]Paracyclophanoyl)aminen mit -Akzeptoren

Zusammenfassung Es wurden die Charge-Transfer-Komplexe einiger substituierter 4-([2.2]Paracyclophanoyl)amine als Donoren mit Tetracyanoethylen (TCNE) und 2,3-Dichlor-5,6-dicyanobenzochinon (DDQ) als -Akzeptoren spektrophotometrisch untersucht. Der Einfluß der Donor-Molekülstrukturen auf ihre Lewis-Basizitäten sowie Ort und Typ der CT-Wechselwirkung werden diskutiert. Es wird über die thermodynamischen Eigenschaften einiger CT-Komplexe und auch über Lösungsmitteleffekte bei der Komplexierung berichtet.

     

Density Functional Theory Study on the Adsorption of CN on Transition Metal M（100） （M = Ni,Pd, Pt,Cu, Ag and Au） Surfaces

The adsorption of cyanide on the top site of a series of transition metal M（100） （M = Cu, Ag, Au, Ni, Pd, Pt） surfaces via carbon and nitrogen atoms respectively, with the CN axis perpendicular to the surface, has been studied by means of density functional theory and cluster model. Geometry, adsorption energy and vibrational frequencies have been determined, and the present calculations show that the adsorption of CN through C-end on metal surface is more favorable than that via N-end for the same surface. The vibrational frequencies of CN for C-down configuration on surface are blue-shifted with respect to the free CN, which is contrary to the change of vibrational frequencies when CN is adsorbed by N-down structure. Furthermore, the charge transfer from surface to CN causes the increase of surface work function.     

Theoretical study of group 11 metal–silonyl complexes: M–SiO and M–(SiO)2 (M = Cu, Ag, or Au)

 The spectroscopic properties of M–SiO and M–(SiO)₂ (1–1 and 1–2 complexes with M = Cu, Ag, or Au) have been theoretically studied. It has been shown that both M–SiO and M–(SiO)₂ compounds in their ground state are bent with a metal–Si bonded structure. The calculated M(ns) spin density agrees well with the electron spin resonance experimental data. From a topological analysis, it has been shown that a rather large charge transfer occurs from the metal towards the SiO moiety, and that the M–Si bond energy correlates with the electron density located at the M–Si bond path (bond critical point). Received: 6 July 2000 / Accepted: 11 October 2000 / Published online: 19 January 2001     

The roles of ligands proton affinity, π-back donation and metal fragment hardness on the Au–N bond in N-donor heterocycles gold(III) complexes

A DFT study on the Au–N interaction for some groups of N-donor heterocycles L {L = pyridines (py), pyrimidines (pm), imidazoles (im), pyrazoles (pz) and isoxazoles (io)} in neutral AuX₃L complexes {AuX₃ = AuBr₃, AuCl₃, trans-AuCl(CN)₂, Au(CN)₃} is reported. Linear relationships between the AuX₃ Mulliken charge in AuX₃L and the computed proton affinity (PA) of the heterocycle were found for all the considered ligands. The different slopes found on changing the N-donor species represent a measure of the π-acidity of these nitrogen ligands once coordinated to the metal centre, by the consequence a π-acceptor ability scale has been derived. The π-acceptor ability of the 5-membered N-donor ligands resulted in all the cases greater than that of the 6-membered N-heterocycles. The proton affinity average value corresponding to a zero charge of the AuX₃ and L fragments in the AuX₃L species has been estimated. This parameter represents the minimum PA value for the formation of a bond between the N-heterocycles and gold(III) and it does not depend on the electronic features of the coordinated ligands. The sensitivity of the AuX₃ fragments towards ligands PA variations follows the order Au(CN)₃ < trans-AuCl(CN)₂ < AuCl₃ < AuBr₃ and this last result has been explained on the basis of the metal fragments relative hardness.     

New π-conjugated polymers based on N-(4-(3,5-bis(4-bromophenyl)-[1,2,4]triazol-4-yl)-phenyl)carbazole: Synthesis and photoluminescent, electroluminescent, and electrochromic properties

New π-conjugated copolyfluorenes carrying main-chain electron-acceptor triazole groups and side-chain electron-donor carbazole fragments are synthesized. All copolymers show solubility in common organic solvents and exhibit high thermal stability and excellent film-forming behavior. The absorption, photoluminescent, electroluminescent, and electrochromic properties of the copolymers are investigated. Polymer films feature stable electrochromic properties as their color changes from yellow in the neutral from to lilac in the oxidized form during a change in the applied voltage from 0 to 1.9 V. In addition, copolyfluorenes demonstrate better electroluminescent properties than the standard homopolylfluorene and offer promise as attractive electroactive materials for use as emitting layers in polymer light-emitting devices.     

New triorganotin(IV) complexes of polyfunctional S,N,O-ligands: Supramolecular structures based on π?π and/or C-H?π interactions

A series of new triorganotin(IV) complexes with 4-hydroxy-2-mercapto-6-methylpyrimidine (L¹H₂), 4-hydroxy-2-mercapto-pyrimidine (L²H₂), 2,4(1H,3H)-pyrimidinedithione (L³H₂) (Scheme 1) of the type R₃SnLSnR₃ (R = Me 1, 4, 7; R = Ph 2, 5, 8; R = PhCH₂3, 6, 9) have been synthesized by reactions of triorganotin(IV) chloride and corresponding ligands. All complexes are characterized by elemental analyses, IR spectra and NMR spectra analyses. Among them, complexes 2, 5 and 8 are also characterized by X-ray crystallography diffraction analyses. Significant π?π stacking, C-H?π interactions and intramolecular hydrogen bonds stabilize these structures.     

Synthesis and spectroscopic study of phenylene-(poly)ethynylenes substituted by amino or amino/cyano groups at terminal(s): electronic effect of cyano group on charge-transfer excitation of acetylenic π-systems

To gain insight into substituent electronic effect on charge-transfer excitation of acetylenic π-systems, phenylene-(poly)ethynylenes substituted by Ph₂N or Ph₂N/cyano groups were synthesized by combination of Sonogashira coupling and double elimination protocol of β-substituted sulfones. These substituted phenyleneethynylenes showed large molar absorption coefficients ?, and emitted strong fluorescence upon UV light irradiation. Phenylene-(poly)ethynylenes, which involve butadiyne or hexatriyne motifs, emitted fluorescence in remarkably lower fluorescence quantum yields Φ_F as their polyethynylene motifs -(CC)_n- expanded. The drastic decrease of fluorescence quantum yields Φ_F were explained in terms of increasing nonradiative reaction rate constants k_nr, which had been determined by the corresponding fluorescence quantum yields Φ_F and lifetime values τ. The emission underwent a large bathochromic shift in polar solvents because the charge-separated excited state is more stabilized than the ground state. Comparison of slope values ρ in Lippert/Mataga plot for the Ph₂N and Ph₂N/cyano-substituted phenylene-(poly)ethynylenes revealed that the latter underwent large change of dipole moments upon photo-excitation although highly expanded acetylenic π-systems with cyano group did little.     

Reactions of azulene and guaiazulene with all-trans-retinal and trans-cinnamaldehyde: comparative studies on spectroscopic, chemical, and electrochemical properties of monocarbenium-ions stabilized by expanded π-electron systems with an azulenyl or 3-guaiazulenyl group

Reaction of azulene (1) with all-trans-retinal in diethyl ether in the presence of hexafluorophosphoric acid at −10 °C for 1 h in a dark room gives the corresponding monocarbenium-ion compound, (2E,4E,6E,8E)-1-azulenyl-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-ylium hexafluorophosphate (3), in 74% isolated yield. The spectroscopic, chemical, and electrochemical properties of 3 compared with those of the previously-documented (2E,4E,6E,8E)-1-(3-guaiazulenyl)-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-ylium hexafluorophosphate (4) are reported. Along with the above delocalized monocarbenium-ion compounds 3 and 4, stabilized by the expanded π-electron systems possessing an azulenyl (or 3-guaiazulenyl) group, an efficient preparation as well as the spectroscopic, chemical, and electrochemical properties of (2E)-1-azulenyl-3-phenyl-2-propen-1-ylium and (2E)-1-(3-guaiazulenyl)-3-phenyl-2-propen-1-ylium hexafluorophosphates (5 and 6) (90 and 96% isolated yields), having a similar partial structure [i.e., the (2E)-1-azulenyl-2-propen-1-ylium-ion or (2E)-1-(3-guaiazulenyl)-2-propen-1-ylium-ion part] to those of 3 and 4, is documented. Moreover, the crystal structure of 6, whose carbenium-ion framework is planar, is shown.     

The effect of methyl group on the cooperativity between three types of hydrogen bond: O?H···O,C?H···O,and O?H···π

The effect of the methyl group on the cooperativity between three types of hydrogen bond (O H···O, C H···O, and O H···π) in cyclic complex involving an acetylene and two waters has been studied on the basis of high-level ab initio calculations. The total interaction energy of three hydrogen bonds increases as the number of methyl group in the complex increases. The binding distances of O H···π and O H···O hydrogen bonds shorten, while that of C H···O hydrogen bond elongates with increasing methyl group. This indicates that addition of methyl group leads to enhancement of O H···π and O H···O hydrogen bonds, and weakening of C H···O hydrogen bond, as also shown in frequency shift, chemical shifts, charge populations, and stabilization energies of orbital interactions. Although the presence of methyl group has a complicated effect on different type of hydrogen bond, the cooperativity of three hydrogen bonds increases in general with the addition of methyl group. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

State of atoms of the transition group elements in dilute solid solutions based on LiMO2 (M = Sc, Ga, Al): III. State of iron and lithium atoms in the LiFe x Sc1−x O2 solid solutions

LiFe _x c_1?x O₂ solid solutions (0.005 < x < 0.10) were studied by the NMR and magnetic susceptibility methods. The anomalies of temperature and concentration dependences of magnetic susceptibility are accounted for by the contributions of single iron atoms and clusters containing iron, oxygen, and lithium atoms. According to the NMR spectroscopy data, lithium atoms also are in two states and enter the cluster composition.     

X-ray crystal structure,spectral and magnetic properties of end-to-end di-μ-thiocyanatobis(imidazole)M(II) polymeric complexes (M=Co,Mn): supramolecular network structure based on N–H ··· S hydrogen bonding and π ··· π stacking

Two isomorphous one-dimensional chain complexes Co(NCS)₂(Him)₂ (1) and Mn(NCS)₂(Him)₂ (2) (Him?=?imidazole) have been prepared and characterized structurally. Both 1 and 2 crystallize in the monoclinic system, space group P2₁/n, and the structures consist of one-dimensional polymeric chains in which metal ions are bridged by two thiocyanate groups bonding in end-to-end fashion. Both 1 and 2 exhibit two-dimensional sheet structures with N–H?···?S hydrogen bonds and three-dimensional supramolecular network structure with π?···?π stacking interactions. IR spectra indicate the presence of bridging thiocyanate groups in both 1 and 2, confirmed by their structures. The variable temperature magnetic susceptibility, measured in the 2–300?K range, indicates weak antiferromagnetic exchange interactions in complex 2.     

New assembly of organic components and transition metal complexes based on [VMo6O22]3? and [V2Mo6O26]6? building blocks: syntheses, crystal structures, and magnetic properties

Two new molybdovanadates, (H₃NCH₂CH₂NH₃)₃ [Mo₆VO₂₂(CH₃COO)₃]·5H₂O (1) and (H₃NCH₂CH₂NH₃)₂{(Mo₆V₂O₂₆)[Cu(NH₂CH₂CH₂NH₂)(H₂O)₂]}·4H₂O (2), have been synthesized in aqueous solution and characterized by IR, UV–vis, single-crystal X-ray diffraction, thermal gravimetric, elemental analysis, and magnetic analysis. Compound 1 is a crown-shaped ring consisted of six edge-sharing MoO₆ octahedra linked to a central {VO₄} unit. The MoO₆ octahedra are in pairs connected with the carboxylato ligands from three acetic acid molecules. Compound 1 is the first example of a molybdovanadate coordinated by acetic acid molecules. In addition, multipoint hydrogen-bonding interactions exist in 1, which bridge the crown-shaped [Mo₆VO₂₂ (CH₃COO)₃]⁶⁻ clusters and the protonated ethylenediamine molecules into three-dimensional (3D) networks. The structural feature of compound 2 is the formation of one-dimensional (1D) zip-zag chain in which [Mo₆V₂O₂₆]⁶⁻ clusters are covalently bonded to copper coordination groups through the terminal oxygen of the {VO₄} tetrahedron. The magnetic investigation on compound 2 demonstrates the possible occurrence of antiferromagnetic interactions by intermolecular linkage.     

Synthesis, crystal structure and electrochemical behavior of tetranuclear transition metal clusters based on lacunary silicotungstates: [M4(H2O)2(SiW9O34)2]10− (M = Ni2+, Co2 +) and [Fe4(μ-O)2(μ-OH)2(SiW10O37)2]14−

Three tetranuclear transition metal clusters based on lacunary silicotungstates [M₄(H₂O)₂(SiW₉O₃₄)₂]^12? (M = Ni²⁺ (1), Co²⁺ (2)), and [Fe₄(μ-O)₂(μ-OH)₂(SiW₁₀O₃₇)₂]^14? (3) have been synthesized under ambient conditions and characterized by elemental analyses, IR, TG, cyclic voltammetry, and single-crystal X-ray diffraction. The polyoxoanions of 1 and 2 are isostructural, including a central rhomb-like {M₄O₁₆} (M = Ni, Co) cluster sandwiched by two trivacant {B-α-SiW₉} Keggin moieties. In the polyoxoanion of 3, two μ-OH and two μ-O bridges link with four Fe^III ions, forming an eight-membered ring. This [Fe₄(μ-OH)₂(μ-O)₂] aggregation is sandwiched by two bi-vacant {α-SiW₁₀} Keggin fragments. The electrochemical properties of the three compounds were investigated.