Dilute Dichloromethane Solution Research Articles

Synthesis and optical properties of 6,10-dihydrofluoreno[2,3-d:6,7-d′]diimidazole derivatives

A series of 10,10-dioctyl-3,6-dihydrofluoreno[2,3-d:6,7-d′]diimidazole derivatives were conveniently synthesized by condensation of the key intermediate 2,3,6,7-tetraamino-9,9-dioctylfluorene (TADOF) with aldehydes under very mild conditions. All of the target compounds were characterized using 1H NMR, 13C NMR, and elemental analysis. The crystal structure of 3,6-dibenzyl-10,10-dioctyl-2,7-diphenyl-6,10-dihydro-3H-fluoreno[2,3-d:6,7-d′]diimidazole was determined as triclinic, space group P-1 type, using single X-ray crystallography. For seventeen samples, UV–visible absorption maximum wavelength (λmax), fluorescence excitation wavelength (λex), fluorescence emission wavelength (λem) and fluorescence quantum yield (φFL) were measured in dilute dichloromethane solution and in the solid state. These compounds possess a medium strong blue fluorescence-emitting ability with φFL values in the region of 0.30–0.89 and structure-optical behavior characteristics were discussed.

A self-complexing and self-assembling pillar[5]arene

A monofunctionalised pillar[5]arene derivative carrying a viologen side chain which exhibits self-complexation in dilute dichloromethane solutions forms supramolecular daisy chain polymers and eventually organogels as its concentration is increased three-fold over the range from 0.1 to 100 mM.

Interaction induced transition in the nanoporous TiO2/Pd‐porphyrin system

AbstractMolecules of Pd(II) 5‐(4‐carboxyphenyl)‐10,15,20‐tris(4‐methylphenyl) porphyrin were adsorbed from highly diluted dichloromethane solution on ultra‐thin layers of nanoporous TiO2 and investigated by modulated surface photovoltage (SPV) spectroscopy. An additional transition with a maximum at 2.03 eV appeared in the SPV spectra after moderate annealing in vacuum irrespective to the amount of adsorbed molecules. The new transition has been ascribed to the formation of a charge transfer complex due to an interaction between the Pd centred porphyrin and Ti surface atoms. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthesis of a Series of Novel Chiral Aromatic Heterocyclic Macrocycles Containing L-Amino Acid and 2,5-Bisphenyl-1,3,4-triazole Subunits

An array of novel chiral aromatic heterocyclic macrocycles, which may show potential enantiomeric recognition to variable D- and L-amino acids, were synthesized in acceptable yield. The desired macrocycles 3a–c and 4a–c were obtained via the condensation reaction of chiral diamine intermediates 2a–c with 2,5-bis(o-chloroformylphenyl)-1,3,4-triazole 5 in a presence of Et3N in a highly diluted dichloromethane solution at room temperature.

A Chemical System that Mimics Decoding Operations

The chemical information stored in equilibrium mixtures of molecular species is larger than the sum of information carried by the individual molecules. Protonation equilibria in dilute dichloromethane solution of a shape-persistent macrocycle bearing two 2,2'-bipyridine units and two Coumarin 2 moieties (see figure) can be exploited to mimic decoding operations.

The light-emitting device consisting of organic white-light components

A material compound, 9,9-bis{4′-[2″-(carbazolyl)-vinyl]-phenyl}fluorene (F-CZV), was specially synthesized and used to fabricate the efficient white organic light-emitting devices (WOLEDs). The absorption peaks appear at 340 nm and 346 nm in dilute dichloromethane solution and film, respectively. The photoluminescence peaks appear at 350 nm and 400 nm in the solution and film, respectively. Photoluminescent quantum yield in solution is ca 0.82 by using quinine sulfate as the standard. In an optimized electroluminescent device structure of ITO/NPB (40 nm)/F-CZV (30 nm)/BPhen (40 nm)/Mg:Ag, the saturated white-light emission was observed at Commission International De L’Eclairage (CIE) coordinates of (0.30, 0.33) at 10 V. The El spectrum of the device is close to independent of the applied driving voltage. It’s maximum brightness and current efficiency is 700 cd/m 2 and 0.41 cd/A, respectively.

Thermotropic liquid crystallinity, thermal decomposition behavior, and aggregated structure of poly(propylene carbonate)/ethyl cellulose blends

AbstractMaleic anhydride end capped poly(propylene carbonate) (PPC‐MA) was blended with ethyl cellulose (EC) by casting from dichloromethane solutions. The thermotropic liquid crystallinity, thermal decomposition behavior, and aggregated structure were investigated by differential scanning calorimetry (DSC), thermogravimetry (TGA), and wide angle X‐ray diffraction (WAXD). DSC exhibits thermotropic liquid crystallinity in the rich EC composition range. TGA shows that thermal decomposition temperatures were elevated upon interfusing EC into PPC‐MA. WAXD corroborates that EC and PPC‐MA/EC blend films cast from dilute dichloromethane solution possessed cholesteric liquid crystalline structure in the rich EC composition range, and that dilution of PPC‐MA with EC increased the dimension of noncrystalline region, leading to a more ordered packed structure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 584–592, 2006

Synthesis of Self-Photosensitizing Polyesters Carrying Pendant Norbornadiene (NBD) Moieties and Benzophenone Groups and Their Photochemical Reactions

Various epoxy monomers containing benzophenone (BP) groups were synthesized by reactions of potassium or lithium salts of BP derivatives with excess epichlorohydrin or epibromohydrin using tetrabutylammonium bromide (TBAB) as a phase transfer catalyst (PTC). The copolymerization of glycidyl 3-(piperidylcarbonyl)-2,5-norbornadiene-2-carboxylate (GPNC), which was prepared by the reaction of epichlorohydrin with potassium carboxylate of a norbornadiene (NBD) derivative using a PTC, and (glycidyloxy)benzophenone with phthalic anhydride (PAn) proceeded in 93% yield using TBAB as a catalyst in sulfolane at 100 °C for 24 h to give self-photosensitizing polyester P-1 containing a pendant NBD moiety and a pendant 4-oxybenzophenone group. Copolymerizations of various epoxy monomers containing certain NBD moieties and BP groups with PAn produced corresponding polyesters with pendant NBD moieties and BP groups in good yields. The photochemical valence isomerizations of the NBD moieties and the photosensitizing isomerizations of the NBD moieties due to the energy transfer from excited BP groups to the NBD moieties in the polymers were performed in the film state or in dichloromethane solution. From this result, it was found that rates of the photochemical isomerization of the NBD moieties in the polymers were strongly enhanced by the introduction of the pendant BP, N-alkyl-N,N‘,N‘-trimethyl-4,4‘-diaminobenzophenone (TBP), group. Furthermore, the photochemical isomerization of the NBD moieties in the polymers having a pendant TBP group proceeded effectively in a diluted dichloromethane solution compared with the mixtures of NBD polymers and low molecular weight photosensitizers such as 4,4‘-bis(N,N-diethylamino)benzophenone. Glass transition temperatures (Tg's) of the prepared polyesters having NBD moieties and stored thermal energy in the corresponding quadricyclane (QC) residues in the polymers were measured by DSC analysis. Then, it was found that Tg's of NBD polyesters were 30−85 °C, and photoirradiated polyesters having QC residues released their stored thermal energies (about 90 kJ/mol) at temperatures above the Tg's of the corresponding NBD polymers.

Self-Assembly of Methyl Zinc (3R)- and (31S)-Bacteriopheophorbides d

The methyl zinc (31R)- and (31S)-[8Et,12Me]bacteriopheophorbides danalogs of the light-harvesting bacteriochlorophylls in photosynthetic bacteriaself-assemble in nonpolar solvents. While in dilute dichloromethane solution both epimers prevail in their monomeric form, complex equilibria of aggregates with gradually red-shifting Qy absorptions are formed at either higher concentration or lower temperature or upon dilution with hexane. Dynamic 1H-NMR and FT-IR spectroscopies show that the 31-hydroxy group participates directly in the self-assembly through oxygen ligation to zinc and through hydrogen bridging to the 131-keto group of the ligated hydroxyls in intermediate unsymmetrical dimers. The basic unit, combining three molecules through >CO···H−O···Zn bonding, and the existence of equilibria between monomers, dimers, and oligomers of varying size depending on the conditions parallel the scheme proposed previously for bacteriochlorophylls c and d (Chiefari, J.; et al. J. Phys. Chem. 1995, 99, 1357−1365. Holzwarth, A. R.; Schaffner, K. Photosynth. Res. 1994, 41, 225−233). In some respects the CD, 1H-NMR, and IR spectral behavior of the two epimers indicates diastereoselective conformational and kinetic differences at the levels of dimers and larger oligomers. Inter alia, the self-assembly of a 1:1 mixture of the (31R) and (31S) epimers proceeds more rapidly than that of the separate epimers. This is possibly of relevance with regard to the rodlike aggregates in the interior of the chlorosomes of certain bacterial species which are composed of both 31-epimeric bacteriochlorophylls.

Time-Resolved Luminescence Anisotropy Studies of the Relaxation Behavior of Polymers. 1. Intramolecular Segmental Relaxation of Poly(methyl methacrylate) and Poly(methyl acrylate) in Dilute Solutions in Dichloromethane

The intramolecular segmental relaxation behaviors of poly(methyl methacrylate) (PMMA) and poly(methyl acrylate) (PMA) in dilute dichloromethane solutions have been studied using time-resolved fluorescence anisotropy measurements (TRAMS). TRAMS have been made on two different spectrometers, incorporating a picosecond laser source and synchrotron, respectively, as excitation sources. Excellent agreement was achieved between the resultant relaxation data, generating confidence both in the spectroscopic procedures involved and in the various forms of analytical data retrieval applied. The relaxation characteristics of each polymer, over the temperature range 230−310 K, was adequately described by an exponential model for the anisotropy, for both acenaphthylene- and 1-vinylnaphthalene-based labels. The associated correlation times for segmental motion exhibited an Arrhenius dependence in the temperature range studied, giving activation energies of the order of 14 and 11 kJ mol-1 for PMMA and PMA, respectively, in dichloromethane. These values are considerably reduced compared to those which have been reported for either polymer in other solvents. The differences in activation parameters are too great to be explained on the assumption that the solvents function to provide frictional resistance alone to the polymer dynamics. It is tentatively suggested that both PMMA and PMA exhibit specific interactions with dichloromethane and/or other solvents, such as toluene. Alternatively, the naphthyl labels used to interrogate the macromolecular dynamics might experience specific interactions with the dichloromethane which distort the apparent behavior of the polymer.

Generation of ionic species by photolysis of polysilylenes in dilute solution

From flash photolysis studies (at λinc = 266 and 347 nm) involving the electrical conductivity and the optical absorption detection method it is inferred that poly(methylphenyl silylene), PMPSi, and poly(biphenylmethyl silylene), PBMSi, form ionic species in a monophotonic process in dilute tetrahydrofuran and dichloromethane solution at 295 K (ϕ(ion) ≈ 4×10−2, PBMSI and 1×10−2, PMPSi, in THF at λinc = 266 nm). The ionic species possess optical absorption bands between 350 and 500 nm with a maximum at about 380 nm. Both the photocurrent and the optical density at 380 nm decay with identical rates by a second order process (k2 ≈ 3 × 1011 dm3 mol−1 s−1, PBMSi in THF at 295 K).

Synthesis and characterization of poly(o-phenetidine) for the fabrication of Langmuir and Langmuir-Blodgett films

The chemical synthesis of a new soluble polyaniline derivative, poly( o-phenetidine), was carried out with monomer excess and the polymer obtained was characterized by elemental analysis, FTIR, UV-vis spectroscopy, gel permeation chromatography, X-ray diffraction and cyclic voltammetry. The poly( o-phenetidine) has chemical and structural properties which are consistent with a pure polymer in the emeraldine oxidation state. Poly( o-phenetidine) Langmuir monolayers were spread from chloroform or dichloromethane solutions on an aqueous solution whose pH was varied from 6 to 2. Because kinetic effects on monolayer compression are extremely important for monolayers from preformed polymers, the influence of the various experimental parameters on the monolayer characteristics was investigated. It is shown that high transfer ratios are obtained in the LB deposition process when Langmuir monolayers are fabricated from very dilute dichloromethane solutions, spread on a low pH subphase, and compressed at a barrier speed of 30 mm min −1. The monolayer is then transferred onto a solid substrate by vertical dipping. UV—visible spectroscopy and cyclic voltammetry of the deposited LB films reveal essentially the same behavior as cast poly( o-phenetidine) films.

Syntheses, spectroscopic, and electrochemical properties of dinuclear copper(II) complexes bridged by a single thiolate sulphur atom; X-ray crystal structures of [Cu2(L1)2(SC6H4Cl-4)][PF6] and [Cu2(L2)2(SC6H4CH3-4)][ClO4

Dinuclear copper(II) complexes [Cu2(L1)2(SR)][PF6]{L1= 3,3′-(trimethylenedinitrilo)bis[butan-2-one oximato (1 –)]; R = C6H4Cl-4(1), C6H4Br-4 (2), or C6H4CH3-4 (3)} and [Cu2(L2)2(SR)][ClO4][L2= difluoro{3,3′-(trimethylenedinitrilo)bis[butan-2-one oximato(2 –)]} borate(1 –); R = C6H4CH3-4 (4), C6H4CH3-2 (5), or C6H4Cl-4 (6)] have been prepared. Single-crystal X-ray structure analyses of (1) and (4) reveal that two copper atoms are bridged by a single thiolate-sulphur atom. Complex (1) crystallizes in space group P, with a= 11.230(3), b= 14.079(3), c= 12.540(3)Å, α= 97.04(2), β= 101.59(2), γ= 72.95(2)°, and Z= 2. Complex (4) crystallizes in space group P, with a= 12.329(6), b= 15.447(6), c= 11.018(7)Å, α= 94.45(5), β= 92.22(5), γ= 96.13(4)°, and Z= 2. The structures of (1) and (4) were refined by least-squares methods to R= 0.064 and 0.089 for 4 416 and 2 167 reflections respectively. In dichloromethane complexes (1)–(6) exhibit absorption bands in the region 320—420 nm due to the thiolate sulphur-to-copper(II) charge-transfer transitions. E.s.r. spectra of these complexes showed a half-band signal due to the Cu–Cu interaction around 1 500 G in dichloromethane–toluene (1 : 1 v/v) at 77 K. The dinuclear structure of the complexes is retained not only in very dilute (ca. 10–5 mol dm–3) dichloromethane solutions but also in the two successive reduced forms, as confirmed by the absorption spectra and cyclic voltammetry, respectively.

On the kinetics of polymer degradation in solution

Poly(2,2,2-trichloroethyl methacrylate), PTCMA, was irradiated in dilute dichloromethane solution with 16 MeV electron pulses of6 0Co γ-rays. Both in the presence and absence of O2, G(S)=9–10 was found at [PTCMA]<9 g/dm3. Indirect and direct radiation effects contributed to main-chain scission at a ratio of 7∶3. In contrast to earlier findings with dioxane solutions, at concentrations of up to 20 g/dm3 indications of crosslinking were not obtained. With CH2Cl2 solutions two modes of light scattering intensity (LSI) decrease were detected indicating the existence of two different macroradicals, one generated by the direct and the other by the indirect action of radiation. These radicals decayed with rate constants of 1.0·103 s−1 and 1.4·101 s−1 and also reacted with C2H5SH with rate constants of 8·104M−1·s−1 and 1·103M−1·s−1, respectively. In O2-saturated solutions both radicals formed peroxyl radicals, PO2, wich combined generating products whose decomposition involved main-chain scission. The combination of PO2-radicals was rate-determining in the consecutive series of reactions as inferred from the 2nd order decrease of the LSI.

Excimer kinetics in poly( n-vinyl carbazole)

The kinetics of excimer formation and decay in dilute dichloromethane solutions of poly( N-vinyl carbazole) have been investigated using time-resolved fluorescence spectroscopy. Further evidence for dual excimer formation in this polymer is presented; interconversion of the excimeric states appears to be a significant process at room temperature.

Molecular complexes of antimony trihalides with benzophenone, 4-Cl-, 4-Br- and 4-NH 2-benzophenone.

With benzophenone (Ph 2CO) and its-Cl- and 4-Br-derivatives, antimony trichloride and tribromide form solid 1:1 molecular complexes; their i.r. spectra show that the metal atom is not coordinated to the CO group. 1:1 complexes too are formed in dilute dichloromethane (DCM) solutions; their equilibrium constants, determined from their charge transger bands by the Benesi—Hildebrand method, decrease in the order Ph 2CO > 4-BrPh 2CO > 4-ClPh 2CO and SbCl 3 > SbBr 3 in agreement with the decreasing dipole moments both of the donors and of the acceptors. The ligand 4-NH 2Ph 2CO forms two solid, yellow and red, complexes with Sb X 3:ligand ratios: 2:1 and 1:2 fpr SbCl 3, 2:3 (:5DCM) and 1:1 for SbBr 3, 2:1 and 1:1 for SbI 3, respectively. The yellow complex becomes spontaneously red in DCM solution and, for SbCl 3, also in the solid state. The i.r. spectra show that also in these complexes the metal atom is not coordinated to the CO group and in the red 1:2 SbCl 3 − and in the yellow 2:1 SbI 3-complex not even to the NH 2 group of the ligand; in the other 4-NH 2Ph 2CO-complexes the ligand seems to be N-bonded to the metal.