共查询到20条相似文献,搜索用时 625 毫秒
1.
Na Liu Ai‐Ling Cheng En‐Qing Gao 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(2):o93-o95
In 3,4‐di‐2‐pyridyl‐1,2,5‐oxadiazole (dpo), C12H8N4O, each molecule resides on a twofold axis and interacts with eight neighbours via four C—H⋯N and four C—H⋯O interactions to generate a three‐dimensional hydrogen‐bonded architecture. In the perchlorate analogue, 2‐[3‐(2‐pyridyl)‐1,2,5‐oxadiazol‐4‐yl]pyridinium perchlorate, C12H9N4O+·ClO4− or [Hdpo]ClO4, the [Hdpo]+ cation is bisected by a crystallographic mirror plane, and the additional H atom in the cation is shared by the two pyridyl N atoms to form a symmetrical intramolecular N⋯H⋯N hydrogen bond. The cations and perchlorate anions are linked through C—H⋯O hydrogen bonds and π–π stacking interactions to form one‐dimensional tubes along the b‐axis direction. 相似文献
2.
Mohamed Ghazzali Vratislav Langer Lars
hrstrm Morsy Abu‐Youssef 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(5):o312-o314
In the crystal structures of the title compounds, C12H12N42+·2BF4−, (I), and C12H11N4+·ClO4−, (II), respectively, infinite two‐ and one‐dimensional architectures are built up via N—H...F [in (I)] and conventional N—H...N [in (II)] hydrogen bonding. The N—N single bond in (I) lies on a crystallographic centre of symmetry; as a result, the two pyridinium rings are parallel. In (II), the pyridinium and pyridyl ring planes are inclined with a dihedral angle of 14.45 (3)°. 相似文献
3.
Electron transfer from excited dyes to N‐alkoxypyridinium salts leads to reductive cleavage of the N−O bond to give an alkoxy radical that can be used to initiate polymerization. Bond‐dissociation energies obtained from calculations based on density‐functional theory are in agreement with predictions from a thermochemical cycle. These data show a difference of ca. 290 – 315 kJ/mol between the BDE of the pyridinium and that of the pyridyl radical and indicate that the fragmentation of the radical is highly exothermic. The energetic requirements for the photochemical electron transfer are discussed in terms of a simplified model that shows that the initiation efficiency of the radical polymerization can be correlated with a single parameter, the reduction potential of the sensitizing dye. Dyes from many classes and with absorption bands spanning the entire visible region were found to be effective in initiating photopolymerization of acrylate monomers in this system. Doubling of the photoresponse can be achieved through coupling of the reductive cleavage of the N‐alkoxypyridinium with an oxidative cleavage of a C−B bond of an alkyltriarylborate, a process that utilizes the chemical potential stored in the oxidized dye following electron transfer to the pyridinium salt. 相似文献
4.
Attempts to use alkylation to introduce a positive charge at the nitrogen atom of the 4‐pyridyl ring in the bis(bidentate) triazole ligand N4‐(4‐pyridyl)‐3,5‐di(2‐pyridyl)‐1,2,4‐triazole ( pydpt ) were made to ascertain what effect a strongly electron‐withdrawing group would have on the magnetic properties of any subsequent iron(II) complexes. Alkylation of pydpt under relatively mild conditions led in some cases to unexpected rearrangement products. Specifically, when benzyl bromide is used as the alkylating agent, and the reaction is carried out in refluxing acetonitrile, the N4 substituent moves to the N1 position. However, when the same reaction is performed in dichloromethane at room temperature, the rearrangement does not occur and the desired product containing an alkylated N4 substituent is obtained. Heating a pure sample of N4‐Bzpydpt?Br to reflux in MeCN resulted in clean conversion to N1Bzpydpt.Br . This is consistent with N4‐Bzpydpt.Br being the kinetic product whereas N1Bzpydpt.Br is the thermodynamic product. When methyl iodide is used as the alkylating agent, the N4 to N1 rearrangement occurs even at room temperature, and at reflux pydpt is doubly alkylated. The observation of the lowest reported temperatures for an N4 to N1 rearrangement is due to this particular rearrangement involving nucleophilic aromatic substitution: a possible mechanism for this transformation is suggested. 相似文献
5.
Kamil Twarg Magorzata Hoyska Andrzej Kochel 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(5):500-506
Employment of the organic 2‐(pyridin‐4‐yl)quinoline‐4‐carboxylic acid ligand with extended coordination capabilities leads to the formation of the one‐dimensional copper(II) coordination polymer catena‐poly[[diaquacopper(II)]‐bis[μ‐2‐(pyridin‐4‐yl)quinoline‐4‐carboxylato]‐κ2N2:O;κ2O:N], {[Cu(C15H9N2O2)2(H2O)2]·2H2O}n, under hydrothermal conditions. The ligand, isolated as its hydrochloride salt, namely, 4‐(4‐carboxyquinolin‐2‐yl)pyridinium chloride monohydrate, C15H11N2O2+·Cl?·H2O, reveals a pseudosymmetry element (translation a/2) in its crystal structure. The additional pyridyl N atom, in comparison with the previously reported analogues with an arene ring instead of the pyridyl ring in the present ligand molecule, promotes the formation of a one‐dimensional coordination polymer, rather than discrete molecules. This polymer shows photoluminescent properties with bathochromic/hypsochromic shifts of the ligand absorption bands, leading to a single band at 479 nm. The CuII ions are involved in weak antiferromagnetic interactions within dimeric units, as evidenced by SQUID magnetometry. 相似文献
6.
A new cadmium–thiocyanate complex, namely catena‐poly[1‐carboxymethyl‐4‐(dimethylamino)pyridinium [cadmium(II)‐tri‐μ‐thiocyanato‐κ4N:S;κ2S:N] [[[4‐(dimethylamino)pyridinium‐1‐acetate‐κ2O,O′]cadmium(II)]‐di‐μ‐thiocyanato‐κ2N:S;κ2S:N]], {(C9H13N2O2)[Cd(NCS)3][Cd(NCS)2(C9H12N2O2)]}n, was synthesized by the reaction of 4‐(dimethylamino)pyridinium‐1‐acetate, cadmium nitrate tetrahydrate and potassium thiocyanide in aqueous solution. In the crystal structure, two types of CdII atoms are observed in distorted octahedral coordination environments. One type of CdII atom is coordinated by two O atoms from the carboxylate group of the 4‐(dimethylamino)pyridinium‐1‐acetate ligand and by two N atoms and two S atoms from four different thiocyanate ligands, while the second type of CdII atom is coordinated by three N atoms and three S atoms from six different thiocyanate ligands. Neighbouring CdII atoms are linked by thiocyanate bridges to form a one‐dimensional zigzag chain and a one‐dimensional coordination polymer. Hydrogen‐bond interactions are involved in the formation of the supramolecular network. 相似文献
7.
A Doubly Zwitterionic Antiaromatic [28]Hexaphyrin Formed upon Deprotonation of 5,20‐Di(N‐methyl‐4‐pyridinium)‐Substituted [28]Hexaphyrin 下载免费PDF全文
A rectangular 5,20‐di(4‐pyridyl) [26]hexaphyrin was reduced with NaBH4 to give the corresponding twisted Möbius aromatic [28]hexaphyrin. Subsequent double N‐methylation gave a dicationic 5,20‐di(N‐methyl‐4‐pyridinium) [28]hexaphyrin, which was converted to a doubly zwitterionic and Hückel antiaromatic [28]hexaphyrin upon deprotonation with sodium methoxide. 相似文献
8.
Varughese Philip E. Manoj M. R. Prathapachandra Kurup Munirathinam Nethaji 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(11):m488-m490
The VV atom in the title complex, [V(C16H16N5S)O2], is five‐coordinate in a highly distorted square‐pyramidal geometry, with the pyridyl N, the azomethine N and the thiolate S atoms of the di‐2‐pyridyl ketone N4,N4‐(butane‐1,4‐diyl)thiosemicarbazone ligand and one oxo ligand occupying the basal coordination positions, while the second oxo ligand occupies the apical position. The molecules are interconnected by weak intermolecular interactions, mainly of the C—H⋯O type, involving the oxo atoms. 相似文献
9.
Jinwon Jeon Yu‐Tao He Sanghoon Shin Sungwoo Hong 《Angewandte Chemie (International ed. in English)》2020,59(1):281-285
The photocatalyzed ortho‐selective migration on a pyridyl ring has been achieved for the site‐selective trifluoromethylative pyridylation of unactivated alkenes. The overall process is initiated by the selective addition of a CF3 radical to the alkene to provide a nucleophilic alkyl radical intermediate, which enables an intramolecular endo addition exclusively to the ortho‐position of the pyridinium salt. Both secondary and tertiary alkyl radicals are well‐suited for addition to the C2‐position of pyridinium salts to ultimately provide synthetically valuable C2‐fluoroalkyl functionalized pyridines. Moreover, the method was successfully applied to the reaction with P‐centered radicals. The utility of this transformation was further demonstrated by the late‐stage functionalization of complex bioactive molecules. 相似文献
10.
Aránzazu Sánchez 《Tetrahedron》2004,60(51):11843-11850
Tris(trimethylsilyl)silane (TTMSS) and azobisisobutironitrile (AIBN) promote the intramolecular heteroarylation of arenesulfonamides with pyridyl radicals under thermal conditions. The arenesulfonamides are easily prepared from pyridinium N-2′-pyridylaminide. The heteroarylation process involves pyridyl radical cyclization and ipso substitution. 相似文献
11.
Synthesis, Characterization and Two-Photon Absorption Properties of a Novel Pyridinium Salt 总被引:2,自引:0,他引:2
A novel pyridinium salt, 2,4-bis[p-(N,N-dimethylamino)styryll-N-metlayl pyridinium iodide (BMSPI) was synthesized and characterized by TG, ^1H NMR spectroscopy and elemental analysis, and the reaction process was studied by using ES-MS. When BMSPI was pumped by a pulsed 1064 nm, 50 ps laser beam, it manifests highly efficient TPA (Two-Photon Absorption) and up-conversion superradiance. The up-conversion efficiency was 6.0% at the pump energy of 4-6 mJ and the lifetime of two-photon fluorescence was measured as 59 ps. 相似文献
12.
Adam Neuba Enver Akin Sonja Herres‐Pawlis Ulrich Flrke Gerald Henkel 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(5):m194-m197
The title compounds, namely 2,6‐bis[(1,3‐dimethylimidazolin‐2‐ylidene)amino]pyridinium perchlorate, C15H24N7+·ClO4−, (I), and bis{2,6‐bis[(1,3‐dimethylimidazolin‐2‐ylidene)amino]pyridinium} μ‐oxido‐bis[trichloridoiron(III)], (C15H24N7)2[Fe2Cl6O], (II), are structurally unusual examples of the organization of molecular units via base pairing. The cations in salts (I) and (II) are derived from the bisguanidine N2,N6‐bis(1,3‐dimethylimidazolin‐2‐ylidene)pyridine‐2,6‐diamine, which associates in centrosymmetric pairs via two N—H...N hydrogen‐bond interactions. N—H...N bridges are formed between the protonated pyridine N atom and one of the nonprotonated guanidine N atoms, with N...H distances of 2.01 (1)–2.10 (1) Å. Compound (I) contains two crystallographically independent cations and anions per asymmetric unit. One of the perchlorate anions is disordered, while the [Fe2Cl6O]2− anion lies on an inversion centre. 相似文献
13.
Diruthenium Complexes of p‐Benzoquinone–Imidazole Hybrid Ligands: Innocent or Noninnocent Behavior of the Quinone Moiety 下载免费PDF全文
《化学:亚洲杂志》2018,13(19):2947-2955
After double deprotonation, 2,6‐diaryl‐p‐benzoquinonodiimidazoles (aryl=4‐tolyl ( I ) or 2‐pyridyl ( II )) were shown to bridge two [Ru(bpy)2]2+ (bpy=2,2′‐bipyridine) complex fragments through the imidazolate N and p‐quinone O ( I → 1 2+) or through the imidazolate N and pyridyl N donor atoms ( II → 2 2+). Characterization by crystal structure analysis, 1H/13C NMR spectroscopy, cyclic and differential pulse voltammetry, and spectroelectrochemistry (UV/Vis/NIR, IR, EPR) in combination with TD‐DFT calculations revealed surprisingly different electronic structures for redox systems 1 n and 2 n. Whereas 1 2+ is reduced to a radical complex with considerable semiquinone character, the reduction of 2 2+ with its exclusive N coordination exhibits little spin on the now redox‐innocent quinone moiety, compared with the electron uptake by the pyridyl–imidazolate chelating site. The first of two close‐lying oxidation processes occurs at the bridging heteroquinone ligand, whereas the second oxidation is partly ( 1 4+) or predominantly ( 2 4+) centered on the metal atoms. 相似文献
14.
Salma Kiani Richard J. Staples Alan B. Packard 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(12):m593-m595
The dimeric title copper(II) complex, diaqua‐1κO,2κO‐bis[3,9‐dimethyl‐6‐(2‐pyridylmethyl)‐4,8‐diazaundeca‐3,8‐diene‐2,10‐dione dioximato(1?)]‐1k4N2,N4,N8,N10;1:2κ5O2:N2,N4,N8,N10‐dicopper(II) diperchlorate, [Cu2(C17H24N5O2)2](ClO4)2, crystallizes with one Cu atom in a square‐pyramidal environment and the other Cu atom displaying a distorted octahedral coordination. In each case, the four N atoms in the core of the ligand (two imine and two oxime N atoms) form the base of the pyramid, with a water molecule at an apex. The two parts of the dimer are linked by an interaction [2.869 (2) Å] between one of the Cu atoms and one of the oxime O atoms coordinated to the second Cu atom, and also by a hydrogen bond between the apical water molecule on the second Cu atom and the pyridyl N atom from the coordination sphere of the first Cu atom. The pyridyl N atoms of the lariat arms are not coordinated to either of the Cu atoms. Thus, this potentially pentadentate ligand is only tetradentate when coordinated to CuII. 相似文献
15.
Yasemin Yüksel Durmaz Görkem Yilmaz Yusuf Yağci 《Journal of polymer science. Part A, Polymer chemistry》2007,45(3):423-428
Photoactive N‐alkoxy 4‐phenyl pyridinium and N‐alkoxy isoquinolinium ion terminated polystyrenes with hexafluoroantimonate counter anion were prepared and characterized. For this purpose, mono‐ and dibrominated polystyrenes were prepared by atom transfer radical polymerization (ATRP). The reaction of these polymers with silver hexafluoroantimonate in the presence of 4‐phenylpyridine N‐oxide and isoquinoline N‐oxide in dichloromethane produced desired polymeric salts with the corresponding functionalities. Irradiation of these photoactive polystyrenes produced alkoxy radicals at chain ends capable of initiating free radical polymerization of methyl methacrylate (MMA). This way, depending on the number of functionality, AB or ABA type block copolymers were formed which were characterized with the aid of gel permeation chromatography and 1H NMR spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 423–428, 2007. 相似文献
16.
Ingrid Socorro Antonia Neels Helen Stoeckli‐Evans 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(1):m13-m15
Bis[μ‐1‐(3‐pyridyl)ethanone oxime‐κ2N:N′]bis[nitratosilver(I)], [Ag2(NO3)2(C7H8N2O)2], crystallizes as a centrosymmetric binuclear macrocylic complex containing silver(I) ions bridged by the organic 1‐(3‐pyridyl)ethanone oxime ligand. The ligand coordinates via the pyridine and the oxime N atoms. A similar metal–ligand arrangement was found in the copper(I) complex catena‐poly[[bis[μ‐1‐(3‐pyridyl)ethanone oxime‐κ2N:N′]dicopper(I)]‐di‐μ‐iodo], [Cu2I2(C7H8N2O)2]n, but here the centrosymmetric macrocycles are connected by double anion bridges, resulting in the formation of a one‐dimensional coordination polymer. 相似文献
17.
Burkhard Schulz Julia Bricks Yan‐Qin Li Ute Resch‐Genger Günter Reck 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(6):o402-o404
1‐Methyl‐2‐[4‐phenyl‐6‐(pyridinium‐2‐yl)pyridin‐2‐yl]pyridinium diperchlorate, C22H19N32+·2ClO4−, (I), and 2‐[4‐(methoxyphenyl)‐2,2′‐bipyridin‐6‐yl]‐1‐methylpyridinium iodide, C23H20N3O+·I−, (II), both crystallize in the monoclinic space group P21/c. In contrast with the monocharged molecule of (II), the doubly charged molecule of (I) contains an additional protonated pyridine ring. One of the two perchlorate counter‐anions of (I) interacts with the cation of (I) via an N—H⋯O hydrogen bond. In (II), two molecules related by a centre of symmetry are connected by weak π–π interactions, forming dimers in the crystal structure. 相似文献
18.
Sophia Lipstman Israel Goldberg 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(10):m371-m373
In the complex diaquatetranitrato[5‐(pyridinium‐4‐yl)‐10,15,20‐tri‐4‐pyridylporphyrin]lanthanum(III) 1,2‐dichlorobenzene trisolvate, [La(NO3)4(C40H27N8)(H2O)2]·3C6H4Cl2, the lanthanum ion is coordinated to one of the peripheral pyridyl substituents of the porphyrin entity. Units of the complex are interlinked to one another in three dimensions by a network of O—H...N, O—H...O and N—H...O hydrogen bonds between the water ligands, nitrate ions, and pyridyl and pyridinium groups of adjacent species. This is the first structural report of an exocyclic complex of the tetrapyridylporphyrin ligand with any lanthanide ion and its self‐assembly into a three‐dimensional architecture sustained by hydrogen bonds. 相似文献
19.
Alan R. Katritzky Clifford H. Watson Zofia Dega-Szafran John R. Eyler 《Journal of mass spectrometry : JMS》1989,24(11):1017-1021
Three novel collisionally induced dissociation pathways, additional to the usual formation of pyridine or pyridinium cation, are described for laser-desorbed N-substituted pyridinium cations. Particularly prevalent is the formation of an ion of m/z 94, corresponding to [PyCH3]+. Doubly charged pyridiniums tend to lose H+, and one example of the apparent formation of the neutral radical C5H6N˙ is reported. 相似文献
20.
Eiji Takahashi Fumio Sanda Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2002,40(8):1037-1046
Novel pyridinium salts [N‐(α‐phenylbenzyl)‐, N‐(1‐naphthylmethyl)‐, or N‐cinnamyl p‐ or o‐cyanopyridinium hexafluoroantimonates] were synthesized by the reaction of p‐ or o‐cyanopyridine and the corresponding bromides followed by anion exchange with KSbF6. These pyridinium salts polymerized epoxy monomers at lower temperatures than previously reported for N‐benzyl‐2‐cyanopyridinium hexafluoroantimonate. The o‐substituted pyridinium salts showed higher activity than the p‐substituted ones, and the crosslinked epoxy polymers cured with these initiators showed higher glass‐transition temperatures. These pyridinium salts photoinitiated radical polymerization as well as cationic polymerization. The photopolymerization was accelerated by the addition of aromatic ketones as photosensitizers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1037–1046, 2002 相似文献