A series of cis-dicyanoosmium(II) complexes [Os(PPh3)2(CN)2(N intersectionN)] (N intersectionN = Ph2phen (2a), bpy (2b), phen (2c), Ph2bpy (2d), tBu2bpy (2e)) and [Os(DMSO)2(CN)2(N intersectionN)] (3a-3e, N intersectionN = Br2phen (3f), Clphen (3g)), were synthesized and their spectroscopic and photophysical properties were examined, and [Os(PMe3)2(CN)2(phen)] (4) with axial PMe3 ligands was similarly prepared. The molecular structures of 2a, 2c, [2c.Zn(NO3)2]infinity, 2d, 2e, 3b, 3d, 3e, and 4 were determined by X-ray crystallographic analyses. The two CN ligands are cis to each other with mean Os-C bond distance of 2.0 A. The two PR3 (R = Ph, Me) or DMSO ligands are trans to each other with P/S-Os-P/S angles of approximately 177 degrees . The UV-vis absorption spectra of 2a-2e display an intense absorption band at 268-315 nm (epsilon = approximately (1.54-4.82) x 104 M-1 cm-1) that are attributed to pi --> pi*(N intersection N) and/or pi --> pi*(PPh3) transitions. The moderately intense absorption bands with lambdamax at 387-460 nm (epsilon = approximately (2.4-11.3) x 103 M(-1) cm(-1)) are attributed to a 1MLCT transition. A weak, broad absorption at 487-600 nm (epsilon = approximately 390-1900 M(-1) cm(-1)) is assigned to a 3MLCT transition. Excitation of 2a-2e in dichloromethane at 420 nm gives an emission with peak maximum at 654-703 nm and lifetime of 0.16-0.67 micros. The emission energies, lifetimes, and quantum yields show solvatochromic responses, and plots of numax, tau, and Phi, respectively, versus ET (solvent polarity parameter) show linear correlations, indicating that the emission is sensitive to the local environment. The broad structureless solid-state emission of 2a-2e at 298 (lambdamax 622-707 nm) and 77 (lambdamax 602-675 nm) K are assigned to 3MLCT excited states. The 77 K MeOH/EtOH (1:4) glassy solutions of 2a-2e also exhibit 3MLCT emissions with lambdamax = 560-585 nm. The 1MLCT absorption and 3MLCT emission of 3a-3g occur at lambdamax = 332-390 nm and 553-644 nm, respectively. In the presence of Zn(NO3)2, both the 1MLCT absorption and 3MLCT emission of 2c in acetonitrile blue-shift from 397 to 341 nm and 651 to 531 nm, respectively. The enhancement of emission intensity (I/Io) of 2e at 531 nm reached a maximum of approximately 810 upon the addition of two equivs of Zn(NO3)2. The crystallographic and spectroscopic evidence suggests that 2c undergoes binding of Zn2+ ions via the cyano moieties. 相似文献
Fluorescence spectra of formycin anhydronucleosides 5,6,8 and of N-dimethylaminomethylene ribonucleosides 1b, 2, 3a-3c and 4 in aqueous solution at 5-7 × 10?5M are reported. Compounds 5 and 6 exhibit a very strong fluorescence emission, ca. 4 and 2 times more intense than that of formycin ( 1a ) accompanied by a bathochromic shift of the emission maximum. Anhydronucleoside 8 also has an increased fluorescence intensity over the parent nucleoside 7 . The level of fluorescence emission is lower in 7 and 8 than in 1a , 5 or 6 . Introduction of N-dimethylaminomethylene group into 1a (compound 1b ) caused a decrease in the fluorescence intensity relative to 1a but a bathochromic shift of the emission maximum. In other instances (compounds 2, 3a-3c, 4 ) the introduction of N-dimethylaminomethylene group led also to fluorescent derivatives. This effect is most pronounced with 2 , whereas the fluorescence intensity of the rest of the group ( 3a-3c and 4 ) is much lower. Compounds 3c and 4 exhibit, however, a profound bathochromic shift in the fluorescence emission maximum relative to 2, 3a or 3b . A possible relationship of the fluorescence emission to the base conformation in formycin and potential use of N-dimethylaminomethylene nucleoside and nucleotide derivatives as fluorescent probes are discussed. J. Heterocyclic Chem., 14 , 135 (1977). 相似文献
Based on design and synthesis of salicylideneaniline derivatives(1a-1d),we demonstrate a prototypical system to investigate the excited-state intramolecular charge transfer(ESICT) coupled excited-state intramolecular proton transfer(ESIPT) reaction via the dipolar functionality of the molecular framework. In solid and aprotic solvents 1a-1d exist mainly as E conformers that possess an intramolecular sixmembered -ring hydrogen bond.Compounds 1a-1c exhibit a unique proton-transfer tautomer emission, while compound 1d exhibits remarkable dual emission due to the different solvent-polarity environment between ESICT and ESIPT states.Time-dependent density functional theory(TDDFT) calculations are reported on these Schiff bases in order to rationalize their electronic structure and absorption spectra. 相似文献
Double the fun! Singlet–triplet dual emission at ambient temperature has been achieved in compounds containing a triarylboron acceptor and an N‐(2′‐pyridyl)‐7‐azaindolyl donor group bridged by a tetrahedral Si linker (see figure). PtII chelation and chelate‐mode switching from N,N to N,C have been found to greatly enhance phosphorescent emission. Furthermore, both singlet and triplet emission bands are responsive to fluoride ions.
A novel photochemical transformation from N-alkyl(p-methoxyphenyl)arylamines (1a-1f) to 1,2,4-trihydro(4aH)-carbazol-3-ones (2a-2f) is reported with the assistance of protonation at the dihydrocarbazole intermediate followed by sequential formal [1,5]hydrogen, [1,3]hydrogen shifts and proton assisted hydrolysis. 相似文献
Anionic conjugated polymer (PFP‐SO) was assembled with a novel enzymatic substrate 6‐O‐modified PNP‐β‐galactoside ( 1 ) for sensitive multiplex enzyme detections. The PFP‐SO/ 1 /lipase/β‐galactosidase system has two chemical input signals which are Input 1 (lipase) and Input 2 (β‐galactosidase), and output optical signals such as fluorescence emission at 416 nm or 450 nm. Four types of logic gates, including YES, INH, NAND and AND, were successfully constructed and utilized for multiplex detections of lipase and β‐galactosidase in one tube.
Intramolecular double‐hydrogen tunneling in porphycene (see picture) is investigated. Low‐temperature conditions are ensured by doping of single molecules into superfluid helium nanodroplets. The investigation of fluorescence excitation and dispersed emission spectra and the highly dissipative environment allows the observation of mode‐selective tunneling splitting and reveals a purely concerted tunneling mechanism for all isotopic variants of porphycene.
Ketoketene thioacetals or cyanoketene thioacetals which were formed by treatment of a variety of active methylenes containing f -keto or f -cyano group with CS 2 or with PhNCS were allowed to react with 2-aminoprop-1-ene-1,1,3-tricarbonitrile under PTC conditions to afford thiopyrano(2,3- b )pyridine 3a-12a or pyrido(2,3- b )pyridine 3b-12b derivatives. 相似文献
Six new asymmetric thiocarbonohydrazones 3a-3f were synthesized from following steps:firstly hydrazine hydrate reacted with carbon disulfide to form thiocarbonohydrazide(1) under microwave irradiation.Then compound(1) reacted with ketone and different aldehydes step by step to give 3a-3f with excellent yields under solvent-free conditions using microwave irradiation.Their structures have been determined by elemental analysis,IR,MS and ~1H NMR data. 相似文献
Polyimides were synthesized from pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), and three different diamines with the following general structure: where R is ethyl, propyl, or isobutyl. The poly(amic acids) obtained had inherent viscosities ranging from 0.30 to 0.93 and were thermally/chemically converted to polyimides. The thermal stability of the polyimides was evaluated by using dynamic thermogravimetric analysis in air. Physical and thermal properties of these polyimides were compared with that obtained by reacting 2,2-bis(4-aminophenyl) propane and PMDA/BTDA. 相似文献
<正>Six new optically active and flame-retardant poly(amide-imide)s PAIs 5a-5f containing phosphine oxide moiety as a flame-retardant unit in the main chain were synthesized from direct polycondensation reaction of six chiral N,N′-(pyromellitoyl)-bis-L-amino acid 3a-3f with bis(3-aminophenyl)phenyl phosphine oxide 4 in a medium consisting of N-methyl-2-pyrrolidone(NMP),triphenyl phosphite(TPP),calcium chloride(CaCl_2) and pyridine.The polymerization reactions produced a series of optically active poly(amide-imide)s with good yield and good inherent viscosity of 0.34-0.70 dLg~(-1).The resulted polymers were fully characterized by means of FTIR and ~1H-NMR spectroscopy,gel permeation chromatography(GPC),elemental analyses,inherent viscosity and solubility tests.Thermal properties and flame-retardant behavior of the PAIs 5a-5f were investigated using thermal gravimetric analysis(TGA and DTG) and limiting oxygen index(LOI).Data obtained by thermal analysis(TGA and DTG) revealed that these polymers showed good thermal stability.Furthermore,high char yield in TGA and good LOI values indicated that the resulting polymers were capable of exhibiting good flame retardant properties.N,N′-(pyromellitoyl)-bis-L-amino acids 3a-3f were prepared in quantitative yields by the condensation reaction of pyromellitic dianhydride(1,2,4,5-benzenetetracarboxylicacid-1,2,4,5-dianhydride) 1 with L-alanine 2a,L-valine 2b,L-leucine 2c,L-isoleucine 2d,L-phenyl alanine 2e and L-2-aminobutyric acid 2f in acetic acid solution. 相似文献
<正>The cationic ring-opening polymerization of 1-azabicyclo[4.2.0]octane,commonly called conidine(1) was studied with some chiral tricyclic amino acid esters(6a-6f) as acylation agents to obtain optically active biopolymers(8a-8f) of the different masses.The structures of the new compounds were confirmed by FT-IR,UV and NMR,and the distribution index of the molecular weights of the polymers was determined from SEC measurements. 相似文献
The photophysical properties of a series of 4,6-diphenyl-2,2'-bipyridyl platinum(II) complexes bearing different σ-alkynyl ancillary ligands (1a-1k) were systematically investigated. All complexes exhibit strong (1)π,π* absorption bands in the UV region; and broad, structureless charge-transfer band(s) in the visible region, which systematically red-shift(s) when the electron-donating ability of the para substituent on the phenylacetylide ligand increases. All complexes are emissive in solution at room temperature. When excited at the charge-transfer absorption band, the complexes exhibit long-lived orange emission (λ(max): 555-601 nm), which is attributed to a triplet metal-to-ligand charge transfer/intraligand charge transfer emission ((3)MLCT/(3)ILCT). Most of these complexes exhibit broad triplet transient difference absorption in the visible to the near-IR region, with a lifetime comparable to those measured from the decay of the (3)MLCT/(3)ILCT emission. The reverse saturable absorption (RSA) of these complexes were demonstrated at 532 nm using nanosecond laser pulses. The degree of RSA follows this trend: 1k ≈ 1a > 1c > 1f ≈ 1i > 1h ≈ 1b > 1e > 1d > 1g, which is mainly determined by the ratio of the triplet excited-state absorption cross section to that of the ground-state and the triplet excited-state quantum yield. 相似文献
A series of cholesterol-appended quinacridone (QA) derivatives 1a-1d have been synthesized,in which 1b and 1c could form stable organogels in a wide range of organic solvents upon ultrasound irradiation.Field emission scanning electronic microscope (FESEM) and transmission electron microscopy (TEM) of xerogels or precipitates indicated that 1b and 1c formed 1D fibrous nanostructure,while 1a assembled into 3D flower-like microstructures.The ultrasound-induced organogel process was characterized by kinetic UV... 相似文献
(E,E,E)‐2,4,6‐Tris(styryl)pyridines 2a‐c with 3, 6 or 9 dodecyloxy substituents were prepared by the highly stereoselective condensation reaction of collidine ( 8 ) and the corresponding phenyl‐(1‐phenyl‐methylidene)amines 7a‐c (Siegrist reaction). In contrast to the corresponding compounds with a benzene or a 1,3,5‐triazine core, 2a‐c do not show any hints for the formation of thermotropic liquid crystals. The major application of such star‐shaped systems is in the field of nonlinear optics. 相似文献
The functionalization of zinc oxide (ZnO) nanoparticles by poly(3‐hexylthiophene) (P3HT) brush is completed by the combination of a mussel inspired biomimetic anchoring group and Huisgen cyclo‐addition “click chemistry.” Herein, the direct coupling of an azide modified catechol derivative with an alkyne end‐functionalized P3HT is described. This macromolecular binding agent is used to access core@corona ZnO@P3HT with a stable and homogeneous conjugated organic corona. Preliminary photoluminescence measurement proves an efficient electron transfer from the donor P3HT to the acceptor ZnO nanoparticles upon grafting, thus demonstrating the potential of such a combination in organic electronics.