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The syntheses of linear and star-shaped bis- and tris(ferrocenyl) derivatives of benzo[1,2-b:4,5-b′]dithiophene and benzo[1,2-b:3,4-b′:5,6-b′′]trithiophene are achieved through one-pot CuI/TMEDA-catalyzed (TMEDA = tetramethylethylenediamine) multiple annulations of bromoethynylbenzenes with sodium sulfide. In addition, the preparation of the parent benzotrithiophene in a good yield with a short reaction time is achieved through the threefold annulation of 1,3,5-trifluoro-2,4,6-tris(trimethylsilyl)ethynylbenzene. The computed structural and electronic features of these ferrocenyl derivatives as well as their UV/Vis spectra and electrochemistry are discussed, and the results provide insights into the effect of the presence of three rather than two ferrocenyl units. To the best of our knowledge, 2,5,8-tris(ferrocenyl)benzo[1,2-b;3,4-b′;5,6-b′′]trithiophene is the first organometallic complex containing benzotrithiophene.

The leather is a durable and flexible protein that can be created by tanning animal rawhide and skins. In this work, a simple method was developed for the functionalization of leather surfaces in terms of excellent coloration and protective properties against micro-organisms and UV radiation. The multifunctional leather surface was obtained through in-situ deposition of silver nanoparticles (Ag NPs) onto the leather surface by employing trisodium citrate (TSC). TSC acts as both a reducing and stabilizing agent. The figuration of Ag NPs in the solutions was evaluated by UV/Vis spectra and the morphology of nanoparticles was determined by TEM. The treated leather samples (Leather/Ag NPs) were evaluated by different tools including SEM, EDX, ATR-FTIR, XRD, TGA, as well as silver content. The impact of the Ag NPs on the coloration, UV-protection, and anti-microbial properties of the leather surface was evaluated. Results disclosed that the nanoparticles are mostly in spherical shapes, regularly distributed, and closely anchored onto the leather surface. The particle size distribution of nanoparticles onto the leather surface was in the range of 55 ± 17 and 130 ± 16 nm for leather/Ag NPs (300 ppm) and leather/Ag NPs (1000 ppm) respectively. The leather/Ag NPs samples were revealed good color properties in terms of color homogeneity, strength as well as excellent fastness properties. The leather/Ag NPs samples were exhibited a yellow/brown color. Moreover, the leather/Ag NPs (1000 ppm) sample was exhibited the highest a* value (6.1 ± 0.8) and b* value (27.8 ± 1.9). The leather/Ag NP sample was showed the highest silver content (1849 ± 3 mg/kg) and much higher UPF value (478 ± 3) than the other samples. Furthermore, the leather/Ag NPs samples were exhibited broad-spectrum antimicrobial activity against different micro-organisms. The leather/Ag NPs (1000 ppm) sample was demonstrated excellent antimicrobial properties with 100% bacterial reduction efficiency against both Gram-positive and Gram-negative bacteria and more than 93% fungal reduction efficiency against Candida albicans

Two tetra-benzimidazolium salts with bridging 9,10-anthraquinone (1 and 2) were synthesized. The crystal structure of 1 was determined by X-ray analysis. One 38-membered macrocycle in 1 was formed by two 9,10-anthraquinone, four benzimidazoliums and six alkylene groups, in which π···π interactions between two anthraquinone were observed. By contrast, compound 2 adopted an open structure, and it was formed by one 9,10-anthraquinone and four benzimidazolium groups, four alkylene groups and two propyl groups. Additionally, the recognition of anions was investigated using 1 (or 2) as chemosensors via fluorescence spectra, UV/vis spectra, HRMS, 1H NMR and IR spectra. The results indicated that compound 1 can distinguish H2PO4− from other anions by the naked eyes (from colorless to yellow under visible light) or by instruments, and compound 2 was able to differentiate H2PO4− from other anions by instruments.

A series of indeno[2,1-b]thiophene-containing organic dyes (IDT1–IDT5) have been synthesized, and their UV/Vis spectra extend beyond 700 nm. These dyes were employed as sensitizers for dye-sensitized solar cells (DSSCs). Among them, dyes IDT3–IDT5 with a thiophene unit conjugated with an anchor have better light harvesting ability and higher JSC values. Dye aggregation contributes substantially to the photocurrent in the near infrared region. The dye IDT5, with chenodeoxycholic acid (CDCA) as the co-adsorbent, has the highest power conversion efficiency (5.06 %) under AM 1.5G simulated sunlight irradiation, which is 68 % of the standard device based on N719 dye.

The CO2-in-water (C/W) microemulsion was formed when the pressure of CO2 was above 4.0 MPa and has been investigated in-situ via high-pressure UV/vis spectra. The spherical mesoporous silica was successfully synthesized in CO2-induced microemulsion. Uniform spherical silica with a diameter of 102 ± 15 nm can be obtained by using C/W microemulsion as a template. It was observed that the BET area and pore volume of the spherical silica were enlarged with increasing the pressure of CO2. Moreover, Pd nanoparticles (Pd NPs) were encapsulated inside the spherical mesoporous silica through one-pot approach. Owing to the particular core–shell structure, this catalyst showed excellent recyclability in the Suzuki coupling reaction when compared with conventional Pd/SiO2 and Pd/C catalysts. The new strategy can be extended as a general approach to prepare other metal nanoparticles encapsulated in spherical mesoporous silica.

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. The synthesis of new molecular complexes of U2+has been pursued to make comparisons in structure, physical properties, and reactivity with the first U2+complex, [K(2.2.2-cryptand)][Cp′3U], 1 (Cp′=C5H4SiMe3). Reduction of Cp″3U [Cp″=C5H3(SiMe3)2] with KC8in the presence of 2.2.2-cryptand or 18-crown-6 generates [K(2.2.2-cryptand)][Cp″3U], 2-K(crypt), or [K(18-crown-6)(THF)2][Cp″3U], 2-K(18c6), respectively. The UV/Vis spectra of 2-K and 1 are similar, and they are much more intense than those of U3+analogues. Variable temperature magnetic susceptibility data for 1 and 2-K(crypt) reveal lower room temperature χMT values relative to the experimental values for the 5f3U3+precursors. Stability studies monitored by UV/Vis spectroscopy show that 2-K(crypt) and 2-K(18c6) have t1/2values of 20 and 15 h at room temperature, respectively, vs. 1.5 h for 1. Complex 2-K(18c6) reacts with H2or PhSiH3to form the uranium hydride, [K(18-crown-6)(THF)2][Cp″3UH], 3. Complexes 1 and 2-K(18c6) both reduce cyclooctatetraene to form uranocene, (C8H8)2U, as well as the U3+byproducts [K(2.2.2-cryptand)][Cp′4U], 4, and Cp″3U, respectively.

We have synthesized a benzene based tripodal receptor containing naphthalene motifs as signaling unit. The receptor can selectively bind Al3+/Pb2+ metal ions with a significant change in its fluorescence and UV/Vis spectra, while the addition of other metal ions (Na+, K+, Ca2+, Mg2+, Cr3+, Hg2, Cu2+, Zn2+, Fe2+, Co2+, Ni2+, Cd2+, and Ag+) produces insignificant or minor changes. The formation of receptor–metal ion complex is also proved by NMR and mass spectroscopic analysis.

A bis(calix[4]pyrrole)-substituted BODIPY ditopic receptor 1 has been synthesised and characterised. The binding and sensing properties of 1 towards several aliphatic and aromatic dicarboxylates have been evaluated by using UV/Vis fluorescence and 1H NMR spectroscopy. The receptor strongly binds linear α,ω-dicarboxylates of appropriate lengths (C9 and C10) by acting as a cleft. For all dicarboxylates, the binding event is detected by a bathochromic shift in the UV/Vis spectra of the receptor and by strong quenching of its fluorescence.

meso-Nitrosubporphyrinatoboron(III) was synthesized by nitration of meso-free subporphyrin with AgNO2 /I2 . The subsequent reduction with a combination of NaBH4 and Pd/C gave meso-aminosubporphyrinatoboron(III). meso-Nitro- and meso-amino-groups significantly influenced the electronic properties of subporphyrin, which has been confirmed by NMR and UV/Vis spectra, electrochemical analysis, and DFT calculations. Oxidation of meso-aminosubporphyrinatoboron(III)s with PbO2 cleanly gave meso-to-meso azosubporphyrinatoboron(III)s that exhibited almost coplanar conformations and large electronic interaction through the azo-bridge.

A novel tripodal fluorescent receptor with benzimidazole motifs as signaling unit is reported. The receptor can selectively bind iodide anion with drastic change in its fluorescence and UV/Vis spectra, while addition of other anions (F−, Cl−, Br−, H2PO4-, SO42-, CH3COO−, NO3- and CN−) does not show any significant change. The formation of receptor–iodide hydrogen bonded complex is proved by NMR titration of the receptor in the presence of iodide anion.

Aromatic oligoamides of 2,6-diaminofluorobenzene and 1,8-diazafluoroanthrancene-2,7-diacid have been synthesized by a convergent method. The heptameric oligoamide can not only fold into a single helix but also hybridize into a highly stable double helix through intensive intermolecular aromatic stackings, which has been extensively characterized in the solid state by single crystal X-ray diffractions and in solution by 1H NMR, NOESY, and UV/vis spectra. The Kdim values of the heptamer are over 107 L mol−1 in various solutions at rt. The extensive interstrand interactions, enlarged diameter (5.4 A), and lower torsion angles (13°) render heptamer 1 readily to hybridize into a highly stable double helix based on spring-like extension mechanism.

Three metal-organic frameworks based on the connectivity co-effect between rigid aromatic dicarboxylic acids and flexible linear linkers have been synthesized and characterized. [Cd(3-NO2-bdc)(bbi)]n (1) and [Co(3-NO2-bdc)(bbi)]n (2) (3-NO2-bdcH2 = 3-nitro-1,2-benzenedicarboxylic acid, bbi = 1,1′-(1,4-butanediyl)bis(imidazole)) are isostructural, which exhibit two-dimensional (2D) layer frameworks; [Co(3,5-pdc)(bbi)·2H2O]n (3) (3,5-pdcH2 = pyridine-3,5-dicarboxylic acid) has 2D 6-connected network with a Schafli symbol of (344653). In addition, compounds 1 and 2 exhibit good photocatalytic activities under visible irradiation, and their different photocatalytic activities have also been analyzed based on the diffuse-reflectance UV/Vis spectra.

The acidity function ( H 0 ) of solutions of trifluoroacetic acid (TFA) in dichloromethane was measured by the indicator method at 298 K in the whole concentration range. The H 0 value for the most acidic solution studied (12.93 M trifluoroacetic acid) is −3.09. The equation describing the dependence of H 0 on the acid concentration was determined. The obtained quantitative data were used for a spectrophotometric study of the basicity of 2,9,16,23-tetra- tert -butylphthalocyanine. Two forms with different UV/vis spectra were observed and their stability constants determined.

This paper describes a new protocol for producing Ag nanocubes of 30 to 70 nm in edge length with the use of CF3COOAg as a precursor to elemental silver. By adding a trace amount of sodium hydrosulfide (NaHS) and hydrochloric acid (HCl) into the polyol synthesis, Ag nanocubes were obtained with good quality, high reproducibility, and on a scale up to 0.19 g per batch for the 70-nm Ag nanocubes. The Ag nanocubes were found to grow in size at a controllable pace over the course of synthesis. The linear relationship between the edge length of the Ag nanocubes and the position of localized surface plasmon resonance (LSPR) peak provides a simple method for finely tuning and controlling the size of the Ag nanocubes by monitoring the UV-vis spectra of the reaction at different times.

By comparing the FIR, MIR, NIR, and vis spectra (pellets) of PrCp*3 (Cp* = η5-C5Me5) (1) with those of LaCp*3 (2) the energies of a number of crystal field (CF) levels of 1 could be determined. The...

Leaves of Liquidambar formosana Hance has been be used as a rice dye for festival food by a small group of people in Guangxi province China. This study evaluated the antioxidant activities of extracts of L. formosana Hance leaves, and the effects of different extract solvents on total phenolics (TP), total flavonoids (TF), and antioxidant potential. The antioxidant activity of the extracts was assessed by using the following methods: in vitro: 1,1-diphenyl-2-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diamonium salt both free radical scavenging assays, reducing, and phosphomolybdenum assays. Antioxidant activity of the synthetic antioxidant butylated hydroxytoluene also was determined in parallel experiments for comparison. All extracts exhibited excellent antioxidant activities and were superior to butylated hydroxytoluene. The antioxidant activity and TP and TF content of various extracts seemed to follow the same trend: ethanolic extract > water extract > acetone extract. This implied that there is a good correlation between antioxidant activities and TP/TF content. In addition, UV/Vis spectra of various extracts were examined to obtain potential antioxidant compounds in assorted extracts.

The work describes the methylation ofchiral and achiral imidazolinium-dithiocarboxylates. The resulting salts qualify as a novel class of ionic liquids after an anion metathesis was performed. Their NMR and UV/Vis spectra were studied.

New FC[SiMe2(CH2)nSiMeFC]2 [FC = 1,1′-ferrocenylene; FC = 1,1′-ferrocenophane, (η5-C5H4)2Fe); n = 2 (7), 3 (8), 6 (9)] and O[SiMe2-X-SiMeFC]2 [X = (CH2)2 (11), CH═CH (13)] have been synthesized and characterized. The synthesis involved the reactions of FCLi2·tmeda with FC[SiMe2(CH2)nSiMeCl2]2 [n = 2 (4), 3 (5), 6 (6)] and O[SiMe2-X-SiMeCl2]2 [X = (CH2)2 (10), CH═CH (12)] at −78 °C. Compounds 4−13 were characterized by elemental analysis, NMR spectroscopy, and for 11, single-crystal X-ray crystallography. The cyclopentadienyl rings in the structure of 11 are tilted with a dihedral angle of 19.8°. The observed red-shift of the lowest energy transition associated with the ferrocenophanyl groups in UV/vis spectra of 7−9, 11, and 13 also confirms the ring strain. Cyclic voltammetric studies exhibited either a broad (7−9) or sharp (11, 13) wave for the reversible redox process. The broadness of the band for the FC-bridged complexes is a composite of the two types of (η5-C5H4)Fe(η5-C5H4) unit, but no significant...

Spiro[fluorene-9,4'-[4H]indeno[3,2-b]thiophene] (spiro-FIT) and bis(spiro-FIT)arenes were synthesized. The UV/ vis spectra, emission spectra, and cyclic voltammetry of these compounds are described.

A new series of benzoylthiourea derivatives of 1, 3, and 5 were prepared, and their chemodosimetric behaviors toward metal cations were investigated in aqueous media at room temperature. Among various metal cations tested, exclusively Hg2+ ion responses to irreversible color changes of receptors, along with distinctive blue shifts in UV/vis spectra. The receptors can be applicable for the monitoring of Hg2+ ion in aqueous solution with a pH span 4-9.

The azulenes 3a,b, 6a,b, 9, 12 and 15 ethynylated in the five-membered ring were prepared by Pd-catalysed cross-coupling of the corresponding iodoazulenes 1a,b, 4a,b, 7, 10 and 13, respectively, with trimethylsilylacetylene and subsequent desilylation. The synthesis of some acyclic oligomers 23–30, 32–36 and 38–40 from these ethynylazulenes could be accomplished by oxidative Eglinton coupling as well as Pd/Cu-catalysed cross-coupling reactions with the appropriate iodoazulenes 1a,b, 4b, 31 and 34. The UV/Vis spectra of the novel oligomers 32, 35 and 36 allow an estimation of the bandgap (Eg) of poly(1,3-azulenylethynylene)s lower than 2 eV. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The 1-mono- and 1,ω-dialkoxy-substituted 2,4-diazapentadienylium, and 2,4,6,8-tetraazanonatetraenylium salts 3, 5, and 10 were synthesized by oxonium salt alkylation of the corresponding 1-oxa-3,5-diazahexatrienes 1, of the 1-oxa-3,5,7-triazaoctatetraenes 4, and of the 1-oxa-3,5,7,9-tetraazadecapentaenes 7. The salts 3 and 10 are sufficiently stable to facilitate their isolation whereas salt 5 decomposes readily. For the synthesis of the alkoxysubstituted 1-oxa-3,5,7,9-tetraazadecapentaenes 7 a new general pathway was developed, which involves the condensation of the salts 3 with the N-acylamidines 6. The structural properties in the crystalline state were determined for the salts 3d and 10a as well as for the neutral compound 7a by X-ray crystallography. All three compounds are characterized by non-planar helical chains, much in contrast to their planar all-carbon analogous polyenes and polymethinium salts. From the UV/Vis spectra we deduce that these compounds prefer non-planar structures also in solution. All stable compounds were completely characterized by analytical and spectroscopic methods.

A series of novel porphyrin–phthalocyanine (Por-Pc) dyads 1–3 have been synthesized by using standard methodologies for unsymmetrically substituted phthalocyanine preparation. These two chromophoric units have been directly linked for the first time, that is, without any spacer, through the β-pyrrolic position of a meso-tetraphenylporphyrin, thus allowing a close proximity of the two units in a rigid arrangement. For this, a novel porphyrin–phthalonitrile precursor 4 had to be prepared. The UV/Vis spectra indicate that the basic electronic characteristics of both individual units (i.e., porphyrin and phthalocyanine) are retained in the hybrid Por-Pc mole

Fourteen isomers of bis(formylmethano)C 60 were isolated and characterized. A mixture of the bisadducts was obtained by the reaction of C 60 with an α-formylsulfonium ylide, and then separated into 15 fractions by preparative HPLC, preparative TLC, and recycling preparative HPLC. Fourteen of the fifteen fractions were found to consist of a single isomer, respectively, which were assigned to the trans -2 (3 diastereo-isomers), trans -3 (3 diastereo-isomers), trans -4 (3 diastereo-isomers), equatorial (2 diastereo-isomers), and cis -2 (3 diastereo-isomers) bisadducts by the comparison of their UV/vis spectra with those of the bisadducts obtained by the Bingel–Hirsch reaction. The 1 H and 13 C NMR analysis, the transformation of the formyl groups, and the dipole moment calculation clarified the stereochemistry of the substituents on the two cyclopropane bridge-head carbons ( in / in , in / out , and out / out ).

Reaction of [PdCl2(DMSO)2], [PtCl2(DMSO)2], and [RuCl2(η4-C8H12)(MeCN)2] with S-acetyl Nβ-acetyldithiocarbazate (=2-acetylhydrazinecarbodithioic acid anhydrosulfide with ethanethioic acid; aadt; 1), S-methyl Nβ-[(5-nitrothiophene-2-yl)methylene]dithiocarbazate (=S-methyl 2-[(5-nitrothiophene-2-yl)methylene]hydrazinecarbodithioate; mntdt; 2), and S-benzyl Nβ-[(5-nitrothiophene-2-yl)methylene]dithiocarbazate (=S-benzyl 2-[(5-nitrothiophene-2-yl)methylene]hydrazinecarbodithioate; bntdt; 3) led to new complexes [PdCl2(L)], [PtCl2(L)], and [RuCl2(η4-C8H12)(L)] (L=ligands 1–3). All these compounds were characterized by elemental analysis, IR, 1H- and 13C-NMR and UV/VIS spectra and thermogravimetric analysis. Ligand 1 coordinates through the thioxo S-atom and the carbazate N(β) atom, whereas in ligands 2 and 3 the thioxo S-atom and the azomethine N-atom are coordinated to the metal ion. Screening of antiamoebic activity of these compounds was performed in vitro against the HK-9 strain of E. histolytica. All the complexes were more active than their respective ligands; compound 3a showed the most promising activity.

A new concept for molecular switches, based on thermal or photochemical double-bond shifts (DBS) in [4n]annulenes such as heptalenes or cyclooctatetraenes, is introduced (cf. Scheme 2). Several heptalene-1,2- and -4,5-dicarboxylates (cf. Scheme 4) with (E)-styryl and Ph groups at C(5) and C(1), or C(4) and C(2), respectively, have been investigated. Several X-ray crystal-structure analyses (cf. Figs. 1–5) showed that the (E)-styryl group occupies in the crystals an almost perfect s-trans-conformation with respect to the CC bond of the (E)-styryl moiety and the adjacent CC bond of the heptalene core. Supplementary 1H-NOE measurements showed that the s-trans-conformations are also adopted in solution (cf. Schemes 6 and 9). Therefore, the DBS process in heptalenes (cf. Schemes 5 and 8) is always accompanied by a 180° torsion of the (E)-styryl group with respect to its adjacent CC bond of the heptalene core. The UV/VIS spectra of the heptalene-1,2- and -4,5-dicarboxylates illustrated that it can indeed be differentiated between an ‘off-state’, which possesses no ‘through-conjugation’ of the π-donor substituent and the corresponding MeOCO group and an ‘on-state’ where this ‘through-conjugation’ is realized. The ‘through-conjugation’, i.e., conjugative interaction via the involved s-cis-butadiene substructure of the heptalene skeleton, is indicated by a strong enhancement of the intensities of the heptalene absorption bands I and II (cf. Tables 3–6). The most impressive examples are the heptalene-dicarboxylates 11a, representing the off-state, and 11b which stands for the on-state (cf. Fig.8).

The UV photolysis of [2.2]paracyclophan-ene (3) and benzo-[2.2]paracyclophan-ene (4), matrix-isolated in argon at 10 K, results in the cleavage of the ethano bridge and formation of compounds 5 and 8, respectively. The IR and UV/Vis spectra are compared with p-xylylene and the benzyl radical as models for a quinoid or diradicaloid structure. The absence of an ESR signal reveals a singlet ground state for these compounds. Remarkable is a sharp absorption in the red part of the visible spectrum which is not observed in the case of p-xylylene or the benzyl radical. The electronic structure can be described as quinoid with a substantial amount of diradicaloid character.

The prepaparation of amorphous, homogeneous blends of zwitterionic polymers with various low molecular weight salts, and in particular with ionic dyes was studied. Homogeneous miscibility was achieved in many cases up to equimolar amounts of salt, even for bulky compounds. Whether miscibility is achieved, or not, depends in a subtle way on the chemical structure of the salt, but no obvious correlation between structure and miscibility could yet be revealed. Spectral shifts of the dye UV/Vis spectra in solution as well as in bulk suggest strong interactions between the polybetaines and the admired salts.

Bicyclo[2.2.2]octadiene (BCOD) fused azuliporphyrins were synthesized by 3+1 porphyrin synthesis of azulitripyrranes with diformylpyrroles. Subsequent retro-Diels-Alder reaction of the BCOD-fused azuliporphyrins afforded azulibenzo-, azulidibenzo-, and azulitribenzoporphyrins 1-5. NMR and UV/Vis spectra, as well as nucleus-independent chemical shift (NICS) calculations revealed that 1-5 and their diprotonated dications exhibit relatively low porphyrinoid aromaticity, which was dependent on the position and number of fused benzene rings present.

A series of heterogeneous photosensitizers has been obtained by immobilization of 4-aminobenzophenone (ABP) within acid zeolites of medium and large pore size. The strong interaction between the amino substituent of ABP and the acid sites of the zeolite is revealed by the red-shift (ca. 50 nm) of the long wavelength absorption band in the UV/Vis spectra of the composites. ABP when included within HZSM-5 (ABP-HZSM-5) behaves as the first shape-selective photosensitizer. Thus, trans-stilbene could be photochemically isomerized to cis-stilbene in the presence of ABP-HZSM-5, while the reverse cis to trans isomerization failed. According to the relative dimensions of the zeolite hosts, ABP incorporated within HY, Hβ and HMOR showed no remarkable difference in the isomerization efficiency of both stilbene isomers.

Symmetrical Azopyridinone Dyes: Synthesis, Spectrophotometrical and Acidobasic Properties, Metal-Complex Formation and Kinetical Investigation of the Azo-Dye Formation The 13 substituted symmetrical azopyridinone dyes 2a–n were synthesized and their VIS spectra measured. The pK*a values of some dyes and of pyridinone coupling components were determined in MeOH/H2O 64:36. The metal-complex formation of the dyes with Cd2+, Zn2+, Co2+, Ni2+, and Cu2+ was investigated, and complex-formation constants of the 1:1 complexes were determined in H2O for 2k (Table 2) and in dimethylformamide/H2O 1:1 for some other azopyridinone dyes (Table 3). The mechanism of the azo-dye formation was investigated and found to be much more complicated than expected. A mechanism of the coupling reaction was developed (see Scheme 4) and fitted by least-squares calculations.

The first 1-silanaphthalene, 4, was successfully synthesized by taking advantage of an efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)-methyl]phenyl (Tbt), and the aromaticity of 4 was discussed on the basis of its 1 H, 1 3 C, and 2 9 Si NMR, Raman, and UV/vis spectra together with theoretical calculations. In contrast to the thermal stability of the Tbt-substituted 2-silanaphthalene 2, 1-Tbt-1-silanaphthalene (4) undergoes a ready [2 + 4] dimerization reaction in solution even at room temperature, despite its stability in the solid state.

The interaction between tetrathiafulvalene and tetracation cyclobis(paraquat-p-phenylene) fragments-the key elements of many rotaxane systems-was investigated theoretically by using ab-initio second-order perturbation methods. In addition to the inclusion complex observed in the solid state, a thermodynamically stable "exterior" complex was identified. Calculation of the UV/Vis spectra for the inclusion and the exterior complexes indicated that the charge-transfer band that is often used to predict the formation of the inclusion complexes in solution is, in reality, due to the exterior mode of complexation. These results suggest that UV/Vis spectroscopy is not a reliable method for assigning the complexation modes in TTF:BB(4+) rotaxanes and related systems.

Polynitroaromatics are well-known to form anionic σ-complexes (Meisenheimer complexes). The formation of such complexes was assumed in the past to explain the blue color of solutions of 2,4-dinitrotoluene (DNT) and amines. However, this work shows that caution is warranted to avoid the hasty misidentification of Meisenheimer complexes. (1)H NMR spectra exhibit no significant shifts in the positions of the DNT protons, indicating that the majority of DNT species in solutions of DNT and amines retain their aromaticity. Density functional calculations on DNT-ethylamine complexes suggest that Meisenheimer complexes are sufficiently high in free energy so that they make up only a very small fraction of the full equilibrium population. While principal component analysis of the UV/vis spectra of the DNT-amine solutions reveals that only one absorbing species of significant concentration is formed, quantitative fits of Job's plots show that 1:1 association of DNT with the amines alone cannot explain the visible absorption spectra. Instead, the Job's plots can be accurately interpreted by deprotonation of DNT, with the amines acting as bases. The deprotonation equilibria lie far on the side of the unreacted DNT, preventing the detection by NMR of the deprotonated minority species that gives the solutions their strong blue color. The analysis of systems with DNT and n-butylamine, diethylamine, triethylamine, or benzylamine provides a consistent pK(a) of DNT in dimethyl sulfoxide of 15.3 ± 0.2.

The nonenzymatic synthesis of aurodrosopterin (5) from 6-acetyl-2-amino-3, 7, 8, 9-tetrahydro-4H-pyrimido-[4,5-b][1,4]diazepin-4-one (3) and 7,8-dihydrolumazine (4) at pH 3 (HCl) was performed. The identity of the synthesized compound with the natural eye pigment isolated from drosophila heads was confirmed by thin-layer chromatography on cellulose and by comparisons of the 1H-NMR and UV/VIS spectra. The nonenzymatic synthesis of a neodrosopterin-like red pigment from 3 and 2,4-diamino-7,8-dihydropteridine was also carried out, but its identity could not be established. This pigment, called aminodrosopterin, has an absorption peak at 489 nm, which is very close to that of neodrosopterin.

The 2,6- (6b, c) and 3,7–substituted 1,5–dimethylbicyclo-[3.3.0]octadienes C2- and Cs-9b and c are brominated by N-bromosuccinimide in the allylic positions to afford the dibromides 7b, exo,exo-7c, 10b and c, respectively. An excess of N-bromosuccinimide converts 10b into the unsymmetrical tetrabromide 11. On chromatography over silica gel, exo,exo-7c is epimerized to endo,endo-7c, while methanolysis occurs on reversed–phase chromatography yielding the dimethoxy compound 8. Under ultrasonic irradiation, the zinc–copper couple converts the bromides 7b, exo,exo-7c, 10c, and 11 into the semibullvalenes 1b, c, 2c, and 12 which are persistent in dilute solutions when atmospheric oxygen is strictly excluded. The UV/Vis spectra of 1b, c, 2c, and 12 have been recorded during reversed–phase HPLC on a Bruker ChromScan detector. Notwithstanding the absence of a classical chromophor, 1c does absorb at no less than 450 nm.

The micellization of amphiphilic molecules is an interesting topic from both theoretical and practical points of view. Herein we have studied the effects of compressed CO(2) on the micellization of Pluronics in water by means of fluorescence, UV/Vis spectra, and small-angle X-ray scattering. It was found that CO(2) can induce the micellization of Pluronics in water, and the micelle can return to the initial state of molecular dispersion after depressurization. Therefore, the micellization of Pluronics in water can be switched through the easy control of pressure. Different from the common micelles with hydrophobic cores, interestingly, this CO(2)-induced micelle has an amphiphilic core, in which hydrophobic and hydrophilic domains coexist. On account of the ability to dissolve both polar and nonpolar components in the micellar core, the CO(2)-induced micelles can improve the reagent compatibilities frequently encountered in various applications. In an attempt to address this advantage, this micelle was utilized as template to the one-step synthesis of Au/silica core-shell composite nanoparticles. Furthermore, the underlying mechanism for the CO(2)-induced micellization of Pluronics in water was investigated by a series of experiments.

The efficient synthesis of (TMS)(2)-[7]helicene (rac-3) and double helicene, a D-2-symmetric dimer of 3,3'-bis(dithieno-[2,3-b:3',2'-d]thiophene) (rac-4) was developed. The crystal structures of 3 and 4 show both strong intermolecular pi-pi interactions and S center dot center dot center dot S interactions. UV/vis spectra reveal that both 3 and 4 show significant pi-electron delocalization.

Halochromic Molecules. Substituted 6,11-Dihydrospiro[[1]benzopyrano[4,3-b]indol-6,9′-9′H-xanthene]-2′,6′-diamines and Their Aza Analogues: New Chromogenes for Black Images. We have synthesized a series of substituted 6,11-dihydrospiro[[1]benzopyrano[4,3-b]indo1-6,9′-9′H-xanthene]-2′,6′-diamines and their respective aza analogues. These compounds develop a black colour in acidic media. The assumed structures of the analytically pure starting and final products are consistant with the fragmentations in the MS and are also supported by FT 1H-NMR. The UV/VIS spectra in buffered MeOH/H2O solutions were measured. From the ϵpH* curves, we determined the pK* values. The title compounds can be used in so-called pressure-sensitive copying systems.

The quest for a new and productive route to matrix-isolated silylene 1 has led to the observation that the presence of nitrogen is favorable, as under such conditions 1 is stabilized by formation of a donor–acceptor complex 1⋅N2. Either matrix photolysis of diazidosilane or pulsed high-vacuum flash pyrolysis of 1,1,1-trimethyldisilane, followed by condensation of the products with nitrogen at 10 K, were applied as synthetic procedures. In a similar manner, complex 1⋅CO can be generated. The results are supported by isotopic-labeling studies. The structural elucidation of the new species is based on the comparison of experimental IR and UV/Vis spectra with data from density functional theory calculations. Silylen 1 wird in Gegenwart von Stickstoff durch Ausbildung eines Donor-Acceptor-Komplexes 1⋅N2 stabilisiert. Dieser Effekt zeigt sich bei der Matrix-Photolyse von Diazidosilan oder bei der Kombination von gepulster Blitzpyyrolyse von 1,1,1-Trimethyldisilan mit anschliesender Co-Kondensation der Produkte zusammen mit Stickstoff bei 10 K. Auf ahnliche Weise kann auch Komplex 1⋅CO dargestellt werden. Die Aussagen werden durch Studien an Isotopomeren der zur Diskussion stehenden Komplexe unterstutzt. Die Strukturaufklarung der neuen Spezies basiert auf dem Vergleich der experimentellen mit berechneten (DFT-Methoden) IR- und UV/Vis-Spektren.

Photon correlation spectroscopy and microelectrophoresis are investigated as tools to characterize SERS-active systems. Mutual relations of SERS spectra, UV/vis spectra, hydrodynamic size and zeta-potential are studied for systems based on Ag sol and two different adsorbates (2,2′-bipyridine and pefloxacin).

Niosomes were prepared by film hydration technique. Gallic acid, 2,4-dihydoxybenzoic acid and 3-hydroxybenzoic acid were used as models. Their encapsulation efficiency followed the order of: gallic acid > 3-hydroxybenzoic acid > 2,4-dihydrobenzoic acid. The structural analysis of solute and UV/Vis spectra results suggested that the type of hydrogen bond between solutes and niosomal membrane might be responsible for these different encapsulation efficiencies.

The structure of precarthamin (1), one of the yellow pigments of safflower petals and a precursor of carthamin (2), was determined on the basis of NMR, mass, and UV/VIS spectra.

The 2(3),9(10),16(17),23(24)-tetrasubstituted metalphthalocyanines 1–7 (M=In, Ni, Zn) were synthesized, as mixtures of four different structural isomers, from the corresponding 4-alkoxy-1,2-dicyanobenzenes and the appropriate metal salts. Separation of the four structural isomers was successfully achieved on a C30 alkyl phase by high-performance liquid chromatography (HPLC). The determination of the point groups of the structural isomers was carried out for 1 and 3, the composition of the structural isomers of 4–7 was accomplished by comparing their retention times and UV/Vis spectra with the data of 1 and 3. For the phthalocyanines 8–10 and the naphthalocyanines 11 and 12 only the C4h and D2h isomers could be separated. Die Synthese von neuen 2,3-tetraalkenyloxy substituierten Phthalocyaninen mit verschieden langen Alkenylketten und unterschiedlichen Zentralmetallen, sowie die Separierung der vier Strukturisomere mittels HPLC (C30-Phase) ist Thema dieser Arbeit. Charakterisierung der einzelnen Isomere erfolgte durch 1H NMR- und UV/Vis-Spektroskopie. Die Untersuchung des sterischen Einflusses der Substituenten sowie der Einflus des Zentralmetalls auf den Trennprozess und die Isomerenzusammensetzung ist hierbei von besonderem Interesse.

In this study, from the fresh leaves of Metaseqouia glyptostroboides flavonoids were extracted by methanol. A flavonoids among these was isolated by cellulose and Sephadex LH-20 column chromatography.The isolated flavonoid was identified by using UV/VIS spectra.

New highly stable benzo-fused m-trifluoromethylphenyl porphyrazines and their complexes with Mg and In were synthesized by cross-condensation of phthalonitrile and bis(m-trifluoromethylphenyl)fumaronitrile. Their 1H and 13C NMR spectra were recorded and described. The Q- and B-bands in the UV/Vis spectra of the metal complexes show the characteristic splitting upon consecutive benzo-annulation. The strong variation of spectral features upon benzo-fusing and metallation/demetallation, as well as the good solubility of the metal complexes in organic solvents, make these materials potentially valuable for optical applications including nonlinear optics. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Die UV/VIS-Spektren des Redoxsystems 1m, (m = 1–5) zeigen fur 1Red und 1ox ahnlichen Verlauf und entsprechen dem Polyentyp. Die Spektren von 1sem unterscheiden sich von diesen stark; die beiden Hauptmaxima wandern pro Vinylengruppe um 110—150 nm nach langeren Wellen. Auch fur andere Radikalionen vom Violentyp gilt λmax ≈m. Sie verhalten sich wie Cyanine, obwohl laut HMO-Rechnungen Ubergange mit Konfigurationswechselwirkung vorliegen. Die Spektren der Azaderivate von 1 werden diskutiert. Eine Methode zur Bestimmung der Semichinonbildungskonstanten aus den spektralen Daten wird beschrieben. Two-step Redox Systems, XIX. – UV/VIS Spectroscopy of Vinylogous and Azavinylogous Redox Systems with 1,3,3-Trimethylindolenine as End Group and a Colour Rule for Violenes The UV/VIS spectra of the redox system 1m, (m = 1 – 5 ) are similar for 1Red and 1ox and display polyene type character. The spectra of 1sem differ sharply. The two main maxima are shifted bathochromically 110–150 nm per vinylene group. Since λmax≈ m is valid for other radical cations of the violene type, they therefore show the behaviour of cyanines, although HMO calculations indicate configuration interaction for the highest electronic transitions. The spectra of the aza derivatives of 1 are discussed and a method for the determination of semiquinone formation constants from spectral data is given.

Die Redoxsysteme 1a und 1b werden auf einem neuen Wege dargestellt und durch ihre UV/VIS-Spektren charackterisiert. Ihre Redoxpotentiale und Semichinonbildungskonstanten KSEM (1a: 3.2·103; 1b: 2.2 · 103) werden mit denen verwandter Systeme verglichen. Multistep Reversible Redox Systems, XLI. - 4,4′-Vinylenebis(pyrylium) Salts The redox systems 1a and 1b are synthesized by a new route and characterized by their UV/VIS spectra. Their redox potentials and semiquinone formation constants KSEM (1a: 3.2·103; 1b: 2.2·103) are compared with those of related systems.

Das Redoxverhalten der kationischen Redoxsysteme 1,n, 2,n, 3,n (n = 0-4) und der verwandten anionischen Redoxsysteme 1,nu (n = 0-4; „Hybridsysteme”) sowie einiger Diazaderivate und des Azoindazols 4 wurden mit verschiedenen elektrochemischen Methoden studiert. Wie beim System A,m nimmt KSem mit wachsender Kettenlange gesetzmasig (von ca. 107 bis ca. 10-2) ab. Die Potentiale E1 und E2 liegen fur 1,n, 2,n und 3,n positiver, fur 1,nu negativer als bei A,m. Die Radikalionen Sem sind kinetisch instabiler als bei A,m. Die UV/VIS-Spektren sind in der Reihe Red

Bis(pentafluorophenyl)ytterbium, prepared from reaction of bis(pentafluorophenyl)mercury with ytterbium metal in tetrahydrofuran (THF), has been isolated as the highly air-sensitive, thermally unstable complex (C6F5)2Yb(THF)4, which yielded pentafluorobenzene on acidolysis. The 19F NMR, IR, and UV/Vis spectra of the complex are discussed. A tetrahydrofuran complex of bis(2,3,5,6-tetrafluorophenyl)ytterbium has been prepared in a similar manner and was identified spectroscopically, thermal instability preventing satisfactory analytical characterization. Reaction was observed between ytterbium and bis(2,3,4,5-tetrafluorophenyl)mercury, but the product decomposed too rapidly for isolation. Ytterbium metal failed to react with diphenylmercury or bis(Dentachlorophenyl)mercury.