Zn(II)-containing metallo-supramolecular polymers: synthesis,photophysical and electrochemical properties

Abstract

Two novel building blocks M1, M2 with different electronic structures, were synthesized based on 2,2′:6′,2″-terpyridine modified with cyano-p-phenylenevinylene (CN-PV) and carbazole moieties through Knoevenagel condensation and Suzuki coupling, respectively. Directed by transition metal ion Zn²⁺, the metallo-homopolymers P1, P2 and metallo-copolymer P3 were obtained via self-assembly polymerization. The structures of the monomers and metallo-supramolecular polymers were fully characterized by MS, ¹H-NMR and ¹³C-NMR. Meanwhile, the UV–vis absorption, photoluminescence (PL) and electrochemical properties of these compounds were systematically investigated. With respect to that of the monomers, both the UV–vis absorption and PL spectra of the polymers are significantly red-shifted. The resulting metallo-supramolecular polymers show similar double absorption peaks (342, 418?nm for P1, 339, 410?nm for P2, and 332, 412?nm for P3), which is caused by the π–π* transition and intramolecular charge transfer (ICT). Further, all the polymers display red-orange emission in toluene and narrow electrochemical energy gaps of 1.46, 1.65 and 1.48?eV for P1, P2, and P3, respectively.     

Synthesis, photophysical properties, and theoretical studies on pyrrole-containing bromo Re(I) complex

Two bromo rhenium(I) carbonyl complexes with the formula of [Re(CO)₃(L)Br], where L = 1,10-phenanthroline (Phen-Re) and 5-(1H-pyrrol-1-yl)-1,10-phenanthroline (Pyph-Re), were successfully synthesized with the aim to analyze the effect of the pyrrole (Py) moiety on the photophysical properties of Pyph-Re. It was found that the triplet metal-to-ligand charge-transfer dπ (Re) → π*(N-N) emission of Phen-Re and Pyph-Re centered at ca. 527 nm with the luminescence quantum yield (LQY) of 0.015 and ca. 578 nm with the LQY of 0.011, respectively. At the same time, the geometrical structures of the ground state and the absorption spectral properties of Phen-Re and Pyph-Re were also calculated with the 6-31G* basis set employed on C, H, N, O, and Br atoms, and LANL2DZ adopted on Re atom. According to the experimental and theoretical analysis, the red-shift of the photoluminescent spectrum and the lower LQY of Pyph-Re should be mainly attributed to the narrower energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital and the more LLCT transition ration of Pyph-Re, respectively.     

Coordination polymers and discrete complexes of Ag(I)-N-(pyridylmethylene)anilines: synthesis,crystal structures and photophysical properties

Reactions of AgO₂C₂F₃ with (E)-N-(pyridylmethylene)aniline in which the pyridyl N is in the p- or m-position yielded two 1-D coordination polymers, [(AgO₂C₂F₃)₂(L_a)₂]_n (L_a = (E)-2,6-diisopropyl-N-(pyrid-3-ylmethylene)aniline) (1) and [(AgOC₂F₃)₂(L_d)₂]_n (L_d = (E)-2,6-diisopropyl-N-(pyrid-4-ylmethylene)aniline) (5), and three discrete complexes, [(AgO₂C₂F₃)₂(L_a)₄] (2), [AgO₂C₂F₃(L_b)₂] (L_b = (E)-N-(pyrid-4-ylmethylene)aniline) (3) and [(AgOC₂F₃)₂(L_c)₄] (L_c = (E)-2,6-dimethyl-N-(pyrid-4-ylmethylene)aniline) (4). The structures were determined by MS, FT-IR and NMR spectroscopies, elemental analysis and single crystal XRD. 1 is an organometallic coordination polymer with silver in η¹-arene coordination, but is a discrete dimeric complex 2 when crystallized from warm diethylether. The geometries around silver(I) in 1 and 4 are tetrahedral, ‘inverted seesaw’ in 2 and T-shaped in 3 and in all the anion seems to play a role. Ag(I) centers in 5 have distorted trigonal bipyramid and inverted seesaw geometries. The trifluoroacetate anions in these complexes display variable monodentate and short bridging coordination patterns. All complexes absorb and strongly emit UV-Vis radiation at room temperature.     

Synthesis and photophysical properties of conjugated polymers with pendant 9,10-anthraquinone units

We have synthesized and investigated the photophysical properties of a series of electron-donor conjugated copolymers with pendant electron-acceptor units. The copolymers consist of diethynyl-1,4-phenylene, fluorene, or phenylene rings alternating with a phenylene unit bearing a pendant 9,10-anthraquinone moiety. The pendant donor-acceptor polymers were designed to have different optical pi-pi* band gaps, while the oxidation potential of the polymer backbone remains approximately constant in the series. The reduction potential of the donor-acceptor polymers is associated with the pendant acceptor units. This leads to the special situation that the electrochemical gap between oxidation and reduction potentials is constant, while the optical band gap decreases, going from PPP, via PPF, to PPE. This design is used to study the effect of the optical gap on the photoinduced electron-transfer reaction that occurs between the main chain electron donor and the pendant acceptor, while the same polymer architecture and energy of the charge separated state are maintained. Fluorescence and photoinduced absorption spectroscopy are used to study the electron transfer following photoexcitation in relation to solvent polarity and in thin solid films. For the fluorene-phenylene alternating copolymer, intramolecular photoinduced electron transfer occurs in the Marcus optimal region.     

Heteroaromatic alanine derivatives bearing (oligo)thiophene units: synthesis and photophysical properties

A series of new benzoxazolylalanine derivatives bearing (oligo)thiophene units at the side chain were synthesized in good yields. The photophysical characterization of these amino acids was performed by UV-vis absorption and fluorescence emission studies and revealed that some of the compounds display high fluorescent quantum yields, making them good candidates for application as fluorescent probes.     

Synthesis, structure, photophysical and electrochemiluminescence properties of Re(I) tricarbonyl complexes incorporating pyrazolyl-pyridyl-based ligands

Three rhenium carbonyl complexes 1-3 were synthesized by reaction of the appropriate bidentate pyrazolyl-pyridyl-based ligand L1, L2 (L1 = 2-[1-{4-(bromomethyl)benzyl}-1H-pyrazol-3-yl]pyridine; L2 = 1,4-bis(3-(2-pyridyl)pyrazol-1-ylmethyl)benzene) with [Re(CO)(5)Cl] in toluene. They were characterized by elemental analyses, ESI-MS, (1)H spectroscopy, and X-ray crystallography for 1 and 2. Compounds 1-3 exhibit bright yellow-green luminescence in the solid state and in solution at 298 K with the lifetimes in the microsecond range. It is noteworthy that the luminescent quantum efficiencies of compounds 1-3 are between 0.040 and 0.051, which are much higher than that of the [Re(bpy)(CO)(3)Cl] complex (= 0.019) (M. M. Richter et al., Anal. Chem., 1996, 68, 4370; J. Van Houten et al., J. Am. Chem. Soc., 1976, 98, 4853). Electrogenerated chemiluminescence (ECL) was observed in solutions of these complexes in the absence or presence of coreactant tri-n-propylamine (TPrA) or 2-(dibutylamino)ethanol (DBAE) by stepping the potential of a Pt disk working electrode. The ECL spectra are identical to the photoluminescence spectra, indicating that the chemical reactions following electrochemical oxidation or reduction form the same (3)MLCT excited states as that generated in the photoluminescence experiments. In most cases, the ECL quantum efficiencies of complexes 1-3 are comparable to that of the [Re(L)(CO)(3)Cl] (L = bpy or phen) system. Oxygen tends to substantially decrease ECL intensities of the three rhenium complexes-TPrA system, which could allow them to be used as oxygen sensors.     

Syntheses, structural characterization and photophysical properties of 4-(2-pyridyl)-1,2,3-triazole rhenium(I) complexes

Novel chelators, i.e., 4-(2-pyridyl)-1,2,3-triazole derivatives, were synthesized by means of Cu(I)-catalyzed 1,3-dipolar cycloaddition and used to prepare luminescent Re(I) complexes [ReCl(CO)(3)(Bn-pyta)], [ReCl(CO)(3)(AcGlc-pyta)] and [ReCl(CO)(3)(Glc-pyta)] (Bn-pyta = 1-benzyl-4-(2-pyridyl)-1,2,3-triazole, AcGlc-pyta = 2-(4-(2-pyridyl)-1,2,3-triazol-1-yl)ethyl 2,3,4,6-tetra-O-acetyl-beta-d-glucopyranoside, Glc-pyta = 2-(4-(2-pyridyl)-1,2,3-triazol-1-yl)ethyl beta-d-glucopyranoside). X-Ray crystallography of Bn-pyta and Glc-pyta indicated an azocompound-like structure while the 1,2,4-triazole isomer has an azine character. [ReCl(CO)(3)(Bn-pyta)] crystallized in the monoclinic system with space group P2(1)/n. Bn-pyta ligand coordinates with the nitrogen atoms of the 2-pyridyl group and the 3-position of 1,2,3-triazole ring, which is a very similar coordinating fashion to that of the 2,2'-bipyridine derivative. The glucoconjugated Re(I) complexes [ReCl(CO)(3)(AcGlc-pyta)] and [ReCl(CO)(3)(Glc-pyta)] hardly crystallized, and were analyzed by applying extended X-ray absorption fine structure (EXAFS) analysis. The EXAFS analyses suggested that the glucoconjugation at the 1-position of the 1,2,3-triazole makes no influence to the coordinating fashion of 4-(2-pyridyl)-1,2,3-triazole. [ReCl(CO)(3)(Bn-pyta)] showed a blue-shifted maximum absorption (333 nm, 3.97 x 10(3) M(-1) cm(-1)) compared with [ReCl(CO)(3)(bpy)] (371 nm, 3.35 x 10(3) M(-1) cm(-1)). These absorptions were clearly assigned to be the mixed metal-ligand-to-ligand charge transfer (MLLCT) on the basis of time-dependent density functional theory calculation. The luminescence spectrum of [ReCl(CO)(3)(Bn-pyta)] also showed this blue-shifted feature when compared with that of [ReCl(CO)(3)(bpy)]. The luminescence lifetime of [ReCl(CO)(3)(Bn-pyta)] was determined to be 8.90 mus in 2-methyltetrahydrofuran at 77 K, which is longer than that of [ReCl(CO)(3)(bpy)] (3.17 micros). The blue-shifted electronic absorption and elongated luminescence lifetime of [ReCl(CO)(3)(Bn-pyta)] suggested that 4-(2-pyridyl)-1,2,3-triazole functions as an electron-rich bidentate chelator.     

Highly emissive pi-conjugated alkynylpyrene oligomers: their synthesis and photophysical properties

We newly prepared para- and meta-linked alkynylpyrene oligomers and examined their photophysical properties. Oligomerization of monomeric building blocks was performed by CuI-promoted oxidative coupling reaction. The resulting oligomers mainly consist of 2-mer to 6-mer that were assigned on the basis of MALDI-TOF mass spectra, and the 2-mer, 3-mer, and 4-mer were isolated and fully characterized. From their absorption and fluorescence spectra, the para-linked oligomers were found to be somewhat pi-conjugated compared with meta-linked ones, and the fluorescence quantum yields decreased with increasing oligomer length (Phif = 0.79-0.55).     

基于含硫芳杂稠环化合物的可溶性共轭齐聚物的合成、表征及其在有机薄膜晶体管中的应用

设计并合成了4个基于含硫芳杂稠环化合物的可溶性共轭齐聚物,即以3-十一烷基苯并[d,d’]噻吩并[3,2-b;4,5-b ’]并二噻吩(BTTT)为末端芳香单元,噻吩(T)、二噻吩(bT)、N-十二烷基-二噻吩并[3,2-b]吡咯(TP)或2,5-双(3-十二烷基噻吩)[3,2-b]并二噻吩 (qT)为中间芳香单元的...     

Concerning the photophysical properties of Re2(4+) and Re2(6+) carboxylate compounds

The preparation and structure of Re(2)(dppm)(2)(O(2)CC(6)H(4)-p-NO(2))(2)Cl(2), where dppm = Ph(2)PCH(2)PPh(2), is reported together with its photophysical properties (absorption, steady state emission, fs- and ns-transient absorption spectroscopy) and electrochemistry. These data are compared with photophysical studies on the previously reported Re(2)(dppm)(2)(O(2)CCH(3))(2)Cl(2). The preparation of the complex Re(2)(O(2)CC(6)H(4)-p-NO(2))(4)Cl(2) is also reported together with its photophysical properties which allows for a comparison of the electronic structures and photophysical states of Re(2)(4+) and Re(2)(6+) containing complexes having MM configurations σ(2)π(4)δ(2)δ(*2) and σ(2)π(4)δ(2), respectively. An interesting comparison is also made with the related MM quadruply bonded complexes of molybdenum and tungsten.     

Highly stable olefin-Cu(I) coordination oligomers and polymers

Highly stable Cu(I)-olefin coordination oligomers and polymers have been successfully prepared and applied to construct metal-organic frameworks (MOFs) with interesting physical and chemical functions in recent years. In this review, we present the olefin-Cu(I) coordination oligomers and polymers and their novel physical properties. From structure to functions, particular emphasis is placed on the coordination and organometallic chemistry of olefin-Cu(I) coordination oligomers and polymers, their structures and potential applications as solids possessing unusual physical functional properties such as electrochemical, chiral separation, fluorescent sensing and ferroelectricity.     

Well-defined enantiopure 1,1'-binaphthyl-based oligomers: synthesis,structure, photophysical properties,and chiral sensing

A series of well-defined enantiopure 1,1'-binaphthyl-based oligomers linked through their 6,6'-positions, ranging from quaternaphthol to decanaphthol, have been synthesized by Suzuki and Stille coupling reactions. These novel oligonaphthyls have been characterized by (1)H and (13)C[(1)H] NMR spectroscopy and high-resolution mass spectrometry. A combination of X-ray structural and CD studies suggests that these oligonaphthyls adopt zigzag but not helical conformations. As the chain length increases, the compounds show enhanced fluorescence. The fluorescence intensity of oligonaphthols is almost 2 orders of magnitude higher than that of 1,1'-bi-2-naphthol and can be effectively and enantioselectively quenched with trans-1,2-diaminocyclohexane with an enantioselectivity factor of 1.24. The present work thus demonstrates the potential of constructing chiral sensory materials based on well-defined enantiopure oligonaphthols.     

Novel core-expanded rylenebis(dicarboximide) dyes bearing pentacene units: facile synthesis and photophysical properties

Two synthetic routes for the benzannulation in the "bay"-region of rylenebis(dicarboximide)s leading to new pi-system-expanded chromophores are described. The first route follows a two-step approach: Suzuki coupling of bromo-substituted perylenebis(dicarboximide) with 2-bromophenylboronic acid, followed by palladium-catalysed dehydrobromination. The second route is best described as a palladium-assisted cycloaddition of benzyne, formed in situ, to the bay-region of the bromo-substituted rylene core. Two new types of core-expanded rylene dyes were synthesised: yellow dibenzocoronenebis(dicarboximide)s, absorbing at 490 nm, and a green dinaphthoquaterrylenebis(dicarboximide), which absorbs at 700 nm. These new chromophores are characterised by significant hypsochromic shifts of absorption, compared to their parent rylenebis(dicarboximide)s, excellent photostabilities and high fluorescence quantum yields.     

The novel rufigallol-based liquid crystals with cholesterol units: synthesis,mesomorphic and photophysical properties

Three novel rufigallol derivatives with four alkyl chains and two cholesteric units 6a, 6b and 6c were prepared in yields of 83–88%. The mesomorphic properties were investigated by DSC, POM and XRD analysis, suggesting that compounds 6a, 6b and 6c possess the ordered hexagonal columnar mesophase. The long alkyl chains contribute to the low phase transition temperature. Sample 6c with four dodecyl chains and two cholesterol units is a room temperature liquid crystal between 31°C and 87°C. Compounds 6a, 6b and 6c also have good fluorescence emission between 400 nm and 500 nm. The studies on CD spectra implied that the chiralities of cholesterol moieties are successfully transferred to the liquid crystalline core. Samples 6a, 6b and 6c are the first fluorescence liquid crystal based on rufigallol core with chiral cholesterol units.     

Computational study of the structure, dynamics, and photophysical properties of conjugated polymers and oligomers under nanoscale confinement

Computational simulations were used to investigate the dynamics and resulting structures of several para-phenylenevinylene (PPV) based polymers and oligomers (PPV, 2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylenevinylene --> MEH-PPV and 2,5,2',5'-tetrahexyloxy-7,8'-dicyano-p-phenylenevinylene --> CN-PPV). The results show how the morphology and structure are controlled to a large extent by the nature of the solute-solvent interactions in the initial solution-phase preparation. Secondary structural organization is induced by using the solution-phase structures to generate solvent-free single molecule nanoparticles. Isolation of these single molecule nanostructures from microdroplets of dilute solution results in the formation of electrostatically oriented nanostructures at a glass surface. Our structural modeling suggests that these oriented nanostructures consist of folded PPV conjugated segments with folds occurring at tetrahedral defects (sp3 C-C bonds) within the polymer chain. This picture is supported by detailed experimental fluorescence and scanning probe microscopy studies. We also present results from a fully quantum theoretical treatment of these systems which support the general conclusion of structure-mediated photophysical properties.     

Synthesis, structural, and photophysical investigation of diimine triscarbonyl Re(I) tetrazolato complexes

The synthesis, structural, and photophysical properties of a novel family of neutral fac-[Re(N(∧)N)(CO)(3)(L)] complexes, where N(∧)N is either 2,2'-bipyridine or 1,10-phenanthroline and L is a para functionalized 5-aryltetrazolate [namely, 5-phenyltetrazolate (Tph(-)), 4-(tetrazolate-5-yl)benzaldehyde (Tbdz(-)), 5-(4-acetylphenyl)tetrazolate (Tacy(-)), and methyl 4-(tetrazolate-5-yl)benzoate (Tmeb(-))] are reported. The complexes were prepared by direct addition of the corresponding tetrazolate anion to the acetonitrile solvated fac-[Re(N(∧)N)(CO)(3)](+) precursor. NMR data demonstrate that the coordination of the metal fragment is regiospecific at the N2 atom of the tetrazolate ring. These conclusions are also supported by X-ray structural determinations. Photophysical data were obtained in diluted and deaerated dichloromethane solutions displaying broad and structureless profiles with emission maxima ranging from 566 to 578 nm. The absorption profiles indicate the presence of higher energy intraligand (IL) π-π* transitions and lower energies ligand-to-ligand charge transfer (LLCT) and metal-to-ligand charge transfer (MLCT). As the last two transitions are mixed, they are better described as a metal-ligand-to-ligand charge transfer (MLLCT), a result that is also supported by density functional theory (DFT) calculations. The complexes show excited state lifetime values ranging from 102 to 955 ns, with associated quantum yield between 0.012 and 0.099. Compared to the parent neutral chloro or bromo [Re(N(∧)N)(CO)(3)X], the complexes show a slightly improved performance because of the π accepting nature of the tetrazolato ligand. The metal-to-ligand backbonding is in fact depleting the Re center of electron density, thus widening the HOMO-LUMO gap and reducing the non-radiative decay mechanism in accordance with the energy gap law. Finally, the electron-withdrawing or donating nature of the substituent on the phenyltetrazolato ligand allows the fine-tuning of the photophysical properties.     

Synthesis and photophysical properties of tetrafluorophenyl-modified carbazole oligomers

A series of tetrafluorophenyl-modified oligo(3,6-carbazole ethynylene)s (CfCzCf, CfCz2Cf, CfCz3Cf, (CfCz)2Cf, and Cf2CzCf2) were synthesized by a Pd/Cu-catalyzed Sonogashira coupling reaction and fully characterized. Their photophysical and electronic properties as well as their thermal stabilities were investigated. It is noteworthy that these tetrafluorophenyl modified compounds showed relative thermal stabilities and low-lying HOMO levels ranging from −5.54 to −5.60 eV, which might be the promising candidates for hole-transporting materials in OLEDs.     

Syntheses,crystal structures,and photophysical properties of two 2-D coordination polymers with different geometries of lead(II)

Two complexes constructed from aromatic acid and N-heterocyclic ligands have been synthesized by hydrothermal reaction: [Pb(cipt)(NDC)]_n (1) [cipt?=?2-(3-chlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, NDC?=?naphthalene-1,4-dicarboxylic acid] and [Pb(ipm)(BDC)₂]_n (2) [BDC?=?terephthalic acid, ipm?=?5-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-2-methoxyphenol]. Single-crystal X-ray analysis shows that 1 exhibits an interesting arm-shaped chain structure. 1-D ladder chain structure is formed by N–H···O bonding interactions and further into a 2-D network by N–H···O hydrogen bonds and interchain π–π stacking interactions. Complex 2 shows a 2-D butterfly wings structure, which has been rarely reported. The structure in 2 has intermolecular N–H···O interactions, which help in construction of the 3-D framework. In 1, the coordination sphere of Pb(II) is hemi-directed, whereas the Pb(II) geometry in 2 is holo-directed. The solid-state fluorescence spectra of 1 and 2 are also investigated, as well as the ligands cipt and ipm.     

pH-Dependent spectroscopic and luminescent properties, and metal-ion recognition studies of Re(I) complexes containing 2-(2'-pyridyl)benzimidazole and 2-(2'-pyridyl)benzimidazolate

A series of Re(I) complexes, [Re(CO)(3)Cl(HPB)] (1), [Re(CO)(3)(PB)H(2)O] (2), [Re(CO)(3)(NO(3))(PB-AuPPh(3))] (3), and [Re(CO)(3)(NO(3))(PB)Au(dppm-H)Au](2) (4) [HPB = 2-(2'-pyridyl)benzimidazole; dppm = 2,2'-bis(diphenylphosphinomethane)], have been synthesized and characterized by X-ray diffraction. Complex 1, which exhibits interesting pH-dependent spectroscopic and luminescent properties, was prepared by reacting Re(CO)(5)Cl with an equimolar amount of 2-(2'-pyridyl)benzimidazole. The imidazole unit in complex 1 can be deprotonated to form the imidazolate unit to give complex 2. Addition of 1 equiv of AuPPh(3)(NO(3)) to complex 2 led to the formation of a heteronuclear complex 3. Addition of a half an equivalent of dppm(Au(NO(3)))(2) to complex 2 yielded 4. In both 3 and 4, the imidazolate unit acts as a multinuclear bridging ligand. Complex 4 is a rare and remarkable example of a Re(2)Au(4) aggregate in combination with μ(3)-bridging 2-(2'-pyridyl)benzimidazolate. Finally, complex 2 has been used to examine the Hg(2+)-recognition event among group 12 metal ions. Its reversibility and selectivity toward Hg(2+) are also examined.