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1.
Various preparations of the neutral radical [CpNi(dddt)] complex (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) were investigated with CpNi sources, [Cp2Ni], [Cp2Ni](BF4), [CpNi(CO)]2, and [CpNi(cod)](BF4), and dithiolene transfer sources, O=C(dddt), the naked dithiolate (dddt(2-)), the monoanion of square-planar Ni dithiolene complex (NBu4)[Ni(dddt)2], and the neutral complex [Ni(dddt)2]. The reaction of [CpNi(cod)](BF4) with (NBu4)[Ni(dddt)2] gave the highest yield for the preparation of [CpNi(dddt)] (86%). [CpNi(ddds)] (ddds = 5,6-dihydro-1,4-dithiin-2,3-diselenolate), [CpNi(dsdt)] (dsdt = 5,6-dihydro-1,4-diselenin-2,3-dithiolate), [CpNi(bdt)] (bdt = 1,2-benzenedithiolate), and [CpNi(bds)] (bds = 1,2-benzenediselenolate) were synthesized by the reactions of [Cp2Ni] with the corresponding neutral Ni dithiolene complexes [Ni(ddds)2]2, [Ni(dsdt)2], [Ni(bdt)2], and [Ni(bds)2], respectively. The five, formally Ni(III), radical complexes oxidize and reduce reversibly. They exhibit, in the neutral state, a strong absorption in the NIR region, from 1000 nm in the dddt/ddds/dsdt series to 720 nm in the bdt/bds series with epsilon values between 2500 and 5000 M(-1) cm(-1). The molecular and solid state structures of the five complexes were determined by X-ray structure analyses. [CpNi(dddt)] and [CpNi(ddds)] are isostructural, while [CpNi(dsdt)] exhibits a closely related structure. Similarly, [CpNi(bdt)] and [CpNi(bds)] are also isostructural. Correlations between structural data and magnetic measurements show the presence of alternated spin chains in [CpNi(dddt)], [CpNi(ddds)], and [CpNi(dsdt)], while a remarkably strong antiferromagnetic interaction in [CpNi(bdt)] and [CpNi(bds)] is attributed to a Cp...Cp face-to-face sigma overlap, an original feature in organometallic radical complexes.  相似文献   

2.
The formally Ni(III) d7 radical organometallic complexes formulated as [CpNi(dithiolene)] can be prepared by different routes involving different CpNi sources such as the Ni(I) [CpNi(CO)]2, the Ni(II) [Cp2Ni] or [CpNi(cod)]+ or the Ni(III) [Cp2Ni]+ complexes. As dithiolene precursors, the naked dithiolate, the mono- as well as bis-(dithiolene) metal complexes were investigated. The highest yields are generally associated with an appropriate redox match, that is a CpNi(II) precursor with a formally Ni(IV) [Ni(dithiolene)2]0 complex, or a CpNi(III) precursor with a formally Ni(III) [Ni(dithiolene)2]? complex. The structural, electrochemical and spectroscopic (UV–vis–NIR, EPR) properties of more than twenty complexes are described and compared, with the help of DFT calculations. They all exhibit a small optical gap with a low-energy absorption band in the Near Infra-Red region, between 700 and 1000 nm. The smaller electrochemical and optical gap found in the [CpNi(dmit)] and [CpNi(dddt)] complexes is correlated with an extensive delocalisation of the spin density in these complexes, while the other members of the series are characterized with a larger and sizeable spin density on the cyclopentadienyl ring.  相似文献   

3.
The compounds [Cp(2)M(S(2)C(2)(H)R)] (M = Mo or W; R = phenyl, pyridin-2-yl, pyridin-3-yl, pyridin-4-yl or quinoxalin-2-yl) and [Cp(2)Mo(S(2)C(2)(Me)(pyridin-2-yl)] have been prepared by a facile and general route for the synthesis of dithiolene complexes, viz. the reaction of [Cp(2)MCl(2)] (M = Mo or W) with the dithiolene pro-ligand generated by reacting the corresponding 4-(R)-1,3-dithiol-2-one with CsOH. These Mo compounds were reported previously (Hsu et al., Inorg. Chem. 1996, 35, 4743); however, the preparative method employed herein is more versatile and generates the compounds in good yield and all of the W compounds are new. Electrochemical investigations have shown that each compound undergoes a diffusion controlled one-electron oxidation (OX(I)) and a one-electron reduction (RED(I)) process; each redox change occurs at a more positive potential for a Mo compound than for its W counterpart. The mono-cations generated by chemical or electrochemical oxidation are stable and the structures of both components of the [Cp(2)Mo(S(2)C(2)(H)R)](+)/[Cp(2)Mo(S(2)C(2)(H)R)] (R = Ph or pyridin-3-yl) redox couples have been determined by X-ray crystallography. For each redox related pair, the changes in the Mo-S, S-C and C-C bond lengths of the {MoSCCS} moiety are generally consistent with OX(I) involving the loss of an electron from a π-orbital that is Mo-S and C-S antibonding and C-C bonding in character. These results have been interpreted successfully within the framework provided by DFT calculations accomplished for [Cp(2)M(S(2)C(2)(H)Ph)](n) (M = Mo or W; n = +1, 0 or -1). The HOMO of the neutral compounds is derived mainly from the dithiolene π(3) orbital (65%); therefore, OX(I) is essentially a dithiolene-based process. The similarity of the potentials for OX(I) (ca. 30 mV) for analogous Mo and W compounds is consistent with this interpretation and the EPR spectra of each of the Mo cations show that the unpaired electron is coupled to the dithiolene proton but relatively weakly to (95,97)Mo. The DFT calculations indicate that the unpaired electron is more localised on the metal in the mono-anions than in the mono-cations. In agreement with this, the EPR spectrum of each of the Mo-containing mono-anions manifests a larger (95,97)Mo coupling (A(iso)) than observed for the corresponding mono-cation and RED(I) for a W compound is significantly (ca. 300 mV) more negative than that of its Mo counterpart. [Cp(2)W(S(2)C(2)(H)(quinoxalin-2-yl))] is anomalous; RED(I) occurs at a potential ca. 230 mV more positive than expected from that of its Mo counterpart and the EPR spectrum of the mono-anion is typical of an organic radical. DFT calculations indicate that these properties arise because the electron is added to a quinoxalin-2-yl π-orbital.  相似文献   

4.
A comparative investigation on five different Cp2Ti(diselenolene) complexes, i.e. Cp2Ti(Se2C2Z2) (Z = -CO2Me), Cp2Ti[Se2C2Z(CF3)], Cp2Ti(bds) (bds = 1,2-benzene-diselenato), Cp2Ti(dsit) (dsit = 1,3-dithiole-2-thione-4,5-diselenato) and Cp2Ti(ddds) (ddds = 5,6-dihydro-1,4-dithiine-2,3-diselenato) is performed based on structural and variable-temperature NMR data. Preparation of Cp2Ti[Se2C2Z(CF3)] involves the reaction of Cp2TiSe5 with an excess of methyl-4,4,4-trifluorotetrolate while Cp2Ti(bds) is obtained from the bds2− diselenolate and Cp2TiCl2. Their X-ray crystal structures have been determined, showing that Cp2Ti(bds) is not isostructural with the sulfur analog Cp2Ti(bdt). Similarly the structures of Cp2Ti(dsit) and Cp2Ti(Se2C2Z2) were also determined from single crystal X-ray diffraction. All complexes exhibit a strong folding of the metallacycle along the Se?Se hinge, ranking from 47.8° in Cp2Ti(Se2C2Z2) to 52.3° in Cp2Ti(ddds). VT NMR investigations on Cp2Ti[Se2C2Z(CF3)] and Cp2Ti(ddds), complementing earlier results on the other complexes, show that the largest activation energies and associated folding angles are observed with the most electron rich diselenolenes (ddds, bds), a behavior closely related to that observed earlier in dithiolene complexes.  相似文献   

5.
Tetraphenoxy-substituted diazadibenzoperylenes 5a,b were synthesized from tetrachloroperylene tetracarboxylic acid bisanhydride 1 through imidization with benzylamine, nucleophilic displacement of the four chlorine atoms by phenolates, carbonyl group reduction by LiAlH(4)/AlCl(3), and subsequent Pd/C-promoted debenzylation-dehydrogenation. The structural properties of these extended diazaarenes are discussed on the basis of a X-ray crystal structure of the N,N'-dibutylated diazadibenzoperylenium dication 6, which revealed a 25 degrees twist of the central six-membered ring leading to an atropisomeric pi-conjugated backbone. The chromophoric systems of 5 and 6 were characterized by optical absorption and fluorescence spectroscopy, which revealed an intense fluorescence with a quantum yield of 75% for 5 and 50% for 6. Cyclic voltammetry showed reversible oxidation and reduction waves for 6, whereas the oxidation of 5 afforded the irreversible deposition of a conductive film on the electrode surface. Finally, the potential use of ligands 5 in supramolecular chemistry has been evaluated by complexation experiments with carboxylic acids and zinc tetraphenylporphyrin (ZnTPP).  相似文献   

6.
Two series of matched and mismatched donor–thiazole–acceptor chromophores have been synthesized to disclose the role that the orientation of the thiazole ring plays on their second-order nonlinear optical (NLO) properties. Whereas previous theoretical studies predict that the matched systems show markedly higher NLO responses, our experimental results do not parallel this trend, showing differences between regioisomers much lower than those predicted.  相似文献   

7.
1-Alkyl-2-{(o-thioalkyl)phenylazo}imidazole (SRaaiNR/, 1) reacts with Co(ClO4)2·6H2O to form [Co(SRaaiNR/)2](ClO4)2 (2). The single crystal X-ray structure of one of the complexes of 2 shows a tridentate chelation N(imidazole), N(azo), S(thioether) system. In the structure one of ClO4 anions shows disorder and forms an (imidazole)C–H···O(ClO3) interaction leading to a 1-D chain. Co(OAc)2.4H2O and SRaaiNR/ react in the presence of NH4SCN (1:1:2 mole ratio) in methanol and the complex [Co(SRaaiNR/)2(SCN)2] (3) has been separated. The single crystal X-ray structure determination has established the structure of the complexes in which the ligand SRaaiNR/ acts in a bidentate N(imidazole), N(azo) chelation mode. A cyclic voltammogram shows a Co(III)/Co(II) oxidative response at 0.6–0.8 V and azo reductions. DFT computation using optimized geometry support the electronic spectral and redox properties of the complexes.  相似文献   

8.
Double-stranded DNA offers multiple binding sites to DNA stains. Measurements of noncovalently bound dye-nucleic acid complexes are, necessarily, measurements of an ensemble of chromophores. Thus, it is difficult to assign fluorescence properties to base-pair-specific binding modes of cyanine dyes or, vice versa, to obtain information about the local environment of cyanines in nucleic acids by using optical spectroscopy. The feasibility to stain DNA and simultaneously probe local perturbations by optical spectroscopy would be a valuable asset to nucleic acid research. So-called FIT probes (forced intercalation probes) were used to pinpoint the location of the DNA stain thiazole orange (TO) in PNADNA duplexes. A detailed analysis of the base-pair dependence of optical properties is provided and enforced binding of TO is compared with "classical" binding of free TO-PRO1. UV-visible absorbance, circular dichroism (CD) and fluorescence spectroscopy, and melting-curve analyses confirmed site-specific TO intercalation. Thiazole orange exhibited base-specific responses that are not observed in noncovalent dye-nucleic acid complexes, such as an extraordinary dependence of the TO extinction coefficient (+/-60 % variation of the averaged epsilon(max) of 57,000 M(-1) cm(-1)) on nearest-neighbor base pairs. TO signals hybridization, as shown by increases in the steady-state fluorescence emission. Studies of TO fluorescence lifetimes in FIT-PNA and in DNADNA and PNADNA complexes highlighted four different fluorescence-decay processes that may be closed or opened in response to matched or single-mismatched hybridization. A very fast decay process (0.04-0.07 ns) and a slow decay process (2.33-3.95 ns) provide reliable monitors of hybridization, and the opening of a fast decay channel (0.22-0.48 ns) that resulted in an attenuation of the fluorescence emission is observed upon the formation of mismatched base pairs.  相似文献   

9.
A recently developed method of synthesis of pi-extended porphyrins made it possible to prepare a series of tetrabenzoporphyrins (TBP) with different numbers of meso-aryl substituents. The photophysical parameters of free-bases and Pd complexes of meso-unsubstituted TBP's, 5,15-diaryl-TBP's (Ar2TBP's) and 5,10,15,20-tetraaryl-TBP's (Ar4TBP's) were measured. For comparison, similarly meso-arylsubstituted porphyrins fused with nonaromatic cyclohexeno-rings, i.e. Ar(n)-tetracyclohexenoporphyrins (Ar(n)TCHP's, n = 0, 2, 4), were also synthesized and studied. Structural information was obtained by ab initio (DFT) calculations and X-ray crystallography. It was found that: 1) Free-base Ar4TBP's are strongly distorted out-of-plane (saddled), possess broadened, red-shifted spectra, short excited-state lifetimes and low fluorescence quantum yields (tau(fl) = 2-3 ns, phi(fl) = 0.02-0.03). These features are characteristic of other nonplanar free-base porphyrins, including Ar4TCHP's. 2) Ar2TBP free-bases possess completely planar geometries, although with significant in-plane deformations. These deformations have practically no effect on the singlet excited-state properties of Ar2TBP's as compared to planar meso-unsubstituted TBP's. Both types of porphyrins retain strong fluorescence (tau(fl) = 10-12 ns, phi(fl) = 0.3-0.4), and their radiative rate constants (k(r)) are 3-4 times higher than those of planar H2TCHP's. 3) Nonplanar deformations dramatically enhance nonradiative decay of triplet states of regular Pd porphyrins. For example, planar PdTCHP phosphoresces with high quantum yield (phi(phos) = 0.45, tau(phos) = 1118 micros), while saddled PdPh4TCHP is practically nonemissive. In contrast, both ruffled and saddled PdAr(n)TBP's retain strong phosphorescence at ambient temperatures (PdPh2TBP: tau(phos) = 496 micros, phi(phos) = 0.15; PdPh4TBP: tau(phos) = 258 micros, phi(phos) = 0.08). It appears that pi-extension is capable of counterbalancing deleterious effects of nonplanar deformations on triplet emissivity of Pd porphyrins.  相似文献   

10.
Jacobsen H  Donahue JP 《Inorganic chemistry》2008,47(21):10037-10045
The molecular and electronic structure of monomeric ([Fe(S2C2H2)2](z), [Fe(S2C2(C6H4-p-OCH3)2)2](z)) and dimeric ([{Fe(S2C2H2)2}2](z)) iron bis(dithiolene) complexes, and of their phosphine adducts ([(PH3)Fe(S2C2H2)2](z), [(P(C6H5)3)Fe(S2C2H2)2](z), [(PH3)Fe(S2C2(C6H4-p-OCH3)2)2](z)), carrying various charges (z = 0, 1-, 2-), have been investigated by density functional theory (DFT). Net total spin polarization values S of zero, two, and four have been considered for all neutral model compounds and their dianions, whereas all monoanions have been examined with net total spin polarization values S of one, three, and five. The DFT calculations utilized the pure functional BP86, as well as the hybrid functionals B3LYP and B3LYP*. For the monomers, the calculations reveal the presence of redox non-innocent dithiolene ligands and antiferromagnetic coupling between the ligands and the metal center. For the dimers, complexes with antiferromagnetically coupled iron centers have been found to represent structures of low energy, if not lowest energy structures. The spin-coupling constant of [{Fe(S2C2H2)2}2](2-) is calculated as J = -230 cm(-1). On the basis of the computational results, a model for reversible, electrochemically controlled binding and release of phosphine ligands to iron bis(dithiolene) complexes is proposed. Only BP86 and B3LYP* results, but not those of B3LYP calculations, are in qualitative agreement with experimental findings. BP86 calculations provide the best quantitative match in comparison with the experiment.  相似文献   

11.
ZnS and Co-doped ZnS nanoparticles have been prepared by simple chemical precipitation method. Zinc acetate, sodium sulfide, and cobalt nitrate have been used as precursors for the preparation of Co-doped ZnS quantum dots. The X-ray diffraction results revealed that the undoped and Co-doped ZnS quantum dots exhibit hexagonal structure. The average grain size of quantum dot was found to lie in the range of 2.6–3.8 nm. The surface morphology has been studied using scanning electron microscope. The compositional analysis results confirm the presence of Co, Zn and S in the sample. The optical properties of undoped and Co-doped ZnS quantum dots have been studied using absorption spectra. TEM results show that undoped and Co-doped ZnS nanoparticles exhibit a uniform size distribution with average size of 2.5–3.4 nm.  相似文献   

12.
A series of new complexes of multi-sulfur 1,2-dithiolene ligands, [Ru(bipy)3][Ni(L)2]2 (bipy?=?2,2′-bipyridine; L?=?pddt (6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate), dddt (5,6-dihydro-1,4-dithiin-2,3-dithiolate)), have been synthesized and characterized. One typical complex, [Ru(bipy)3][Ni(pddt)2]2·2H2O (1), crystallized in an acentric space group of P212121, with the cell dimensions of a?=?8.634(1), b?=?14.560(1), c?=?49.889(5)?Å, α?=?β?=?γ?=?90°, and Z?=?4. It consists of alternating columns of cations and anions along the a direction. The structure was refined by full matrix least squares methods to R 1?=?0.0340, wR 2?=?0.0670. Magnetic studies on [Ph2Cr][Ni(dddt)2] are also reported.  相似文献   

13.
Well‐ordered single, double/four parallel, three/four‐strands helical chains, and five‐strand helical chain with a single atom chain at the center of Si nanowires (NWs) inside single‐walled carbon nanotubes (Sin@SWCNTs) are obtained by means of molecular dynamics. On the basis of these optimized structures, the structural evolution of Sin@SWCNTs subjected to axial stress at low temperature is also investigated. Interestingly, the double parallel chains depart at the center and transform into two perpendicular parts, the helical shell transformed into chain, and the strand number of Si NWs increases during the stress load. Through analyzis of pair correlation function (PCF), the density of states (DOS), and the z‐axis polarized absorption spectra of Sin@SWCNTs, we find that the behavior of Sin@SWCNTs under stress strongly depends on SWCNTs' symmetry, diameter, as well as the shape of NWs, which provide valuable information for potential application in high pressure cases such as seabed cable. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009  相似文献   

14.
Versatile graphdiyne (GDY) substrate has been modified by numerous transition metals and resulting composites showed excellent photo/electro-catalytic performance. However, GDY materials modified by actinides that are stockpiled waste product due to large-scale use in nuclear industry, are particularly scarce and remains great challenge. To deeply understand the structural properties, GDY complexating actinyl (AnmO2)n+ (An = U, Np, Pu; m = VI, V) species with its atomistic pore was investigated by relativistic density functional theory (DFT). The GDY pore was found suitable to hold actinyl species, by forming organometallic AnC dative bonds. This chemical coupling interaction was further confirmed by quantum theory of atoms-in-molecule and electronic structure calculations. The GDY-uranyl(V), for instance, shows a π(UC) bonding HOMO, which is anticipated to improve electron transfer between ligand and metal. Orbital structures and compositions of complexes suggest their implication towards catalysis, which were further corroborated by calculations on redox potentials of GDY-actinyl complexes. Hence, our results show the potential applications of GDY complexating actinyl species towards novel catalytic surfaces.  相似文献   

15.
Dithia[3.3](4,9)benzenopyrenophanes carrying various functional groups at the inner position or the outer position of the benzene ring have been prepared. The pyrenophanes with the substituent at the inner position of the opposite benzene ring exhibit the conformation in which the pyrene and the benzene components exist in the parallel manner (parallel conformation). On the contrary the conformation characterized by the perpendicular orientation of the pyrene and the benzene components has been confirmed for the pyrenophanes having the substituent at the outer position of the opposite benzene ring (perpendicular conformation). The NH-pi interaction between the inner amino group on the opposite benzene ring and the pyrene ring was observed. Formation of charge-transfer complexes of the pyrenophanes and tetracyanoethylene (TCNE) was performed. It has been found out that the orientation of two aromatic components and the NH-pi interaction as well as the electronic nature of the substituent on the opposite benzene ring significantly affect characteristics of the charge-transfer complexes in this pyrenophane system.  相似文献   

16.
2,3,6,7-tetrabromonaphthalene dianhydride has been synthesized by the bromination of naphthalene dianhydride with dibromoisocyanuric acid in excellent yield. The condensation of this dianhydride with 2,6-diisopropylaniline yielded the corresponding tetrabromo-substituted naphthalene diimide (NDI), which is a versatile precursor for the synthesis of core-tetrafunctionalized NDIs. Nucleophilic substitution of tetrabromo NDI with alkoxy, alkylthio, and alkylamino nucleophiles afforded a series of core-tetrasubstituted NDI chromophores that complete the series of previously reported di- and trifunctionalized NDI derivatives. The effects of electronic nature and number of core substituents on the optical and electrochemical properties of NDIs have been investigated by UV-vis and fluorescence spectroscopy and cyclic voltammetry. The absorption maxima (629-642 nm) of tetraamino NDIs are strongly bathochromically shifted compared to those of other core-functionalized NDIs.  相似文献   

17.
采用密度泛函理论B3LYP/6-311G**方法,对一系列含Schiff碱基噻唑衍生物的二阶非线性光学(NLO)性质和电子光谱进行了研究.结果表明,分子中推、拉电子取代基强度的提高,噻唑环数的增加以及Schiff碱基的引入有利于提高分子的βtot值.光谱数据显示,分子中HOMO轨道向LUMO,LUMO+2及LUMO+3轨道的电子跃迁对分子的电子光谱有重要贡献.该系列化合物由于具有较大的二阶NLO响应与良好的透光范围,可以作为潜在的NLO材料.  相似文献   

18.
Undoped and manganese doped ZnO (ZnO:Mn) films were prepared by sol gel method using spin coating technique. The effect of Mn incorporation on the structural and optical properties of the ZnO film has been investigated. The crystalline structure and orientation of the films have been investigated by using their X-ray diffraction spectra. The films exhibit a polycrystalline structure. Mn incorporation led to substantial changes in the structural characteristics of the ZnO film. The scanning electron microscopy (SEM) images of the films showed that the surface morphology of the ZnO film was affected by the Mn incorporation. The transparency of the ZnO film decreased with the Mn incorporation. The optical band gap and Urbach energy values of the ZnO and ZnO:Mn films were found to be 3.22, 3.19 eV and 0.10, 0.23 eV, respectively. The optical constants of these films, such as refractive index, extinction coefficient and optical dielectric constants were determined using transmittance and reflectance spectra. The refractive index dispersion curve of the films obeys the single oscillator model with dispersion parameters. The oscillator energy, E o , and dispersion energy, E d, of the films were determined 5.30 and 16.26 eV for ZnO film and 5.80 and 12.14 eV for ZnO:Mn film, respectively.  相似文献   

19.
A series of metal naphthalocyanine complexes (M = TiO2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Ru2+) have been investigated using density functional theory (DFT) and time-dependent DFT methods in vacuo and in the solvent dimethylsulfoxide in order to evaluate the influence of the different metal atoms on the geometries and optical properties of their complexes. The optimized geometries for the complexes without an axial ligand exhibit planar conformations. Most of the absorption bands of the metal complexes are blue-shifted compared to those of the metal-free naphthalocyanine, both in vacuo and in the solvent. The various transition metals could gradually tune the electronic and spectroscopic properties of their naphthalocyanine complexes, which may provide valuable information for tuning the properties of naphthalocyanine complexes for various applications.  相似文献   

20.
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