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1.
In this study, green phosphorescent Pt(II) complexes with N,N‐diphenyl‐6‐(1H‐pyrazol‐1‐yl)pyridin‐2‐amine (Ndpp) coordinated ligands, [Pt (Ndpp)Cl] 2a , [Pt (Ndpp)Pb, Pb = (prop‐1‐ynyl)benzene] 2b , and [Pt (Ndpp)CN] 2a? CN were theoretically investigated by means of density functional theory and time‐dependent density functional theory calculations to reveal their marked distinct phosphorescence quantum yields. These complexes exhibit evident absorption bands in the 200–450 nm region but emit strong green light with marked differences of phosphorescence quantum yields. Compared with the complex 2a , the complex 2b possesses large oscillator strengths of absorption spectra, strong spin‐orbit coupling, and transition electric dipole moment, as well as small singlet‐triplet splitting energies, which conduces to enhancing its radiative decay. To illustrate the nonradiative decay process, the transition state (TS) between the triplet metal‐centered (3MC) state and the excited state (T1) was optimized. The 3MC state is found to be the minimum energy crossing point (MECP) between the T1 state and the S0 state. Compared with the complex 2a , the complex 2b possesses a much larger energy barrier to the MECP state from the T1 state, so it is strongly emissive in the green region. Besides, the introduction of ? CN substitutions on 2a is useful for enhancing the energy barrier to the thermal deactivation pathway of 3MLCT → TS → MECP. These results demonstrate that the modification of metal–ligand conjugation is an effective way to develop high‐performance phosphorescent materials.  相似文献   

2.
Biologically active triazole Schiff bases ( L 1  L 3 ) derived from the reaction of 3‐amino‐1,2,4‐triazole with chloro‐, bromo‐ and nitro‐ substituted salicylaldehydes and their Zn(II) complexes (1–3) have been synthesized and characterized by their physical, spectral and analytical data. Triazole Schiff bases potentially act as tridentate ligands and coordinate with the Zn(II) metal atom through salicylidene‐O, azomethine‐N and triazole‐N. The complexes have the general formula [M(L‐H)2], where M = zinc(II) and L = ( L 1 – L 3 ), and observe an octahedral geometry. The Schiff bases and their Zn(II) complexes have been screened for in‐vitro antibacterial, antifungal and brine shrimp bioassay. The biological activity data show the Zn(II) complexes to be more potent antibacterial and antifungal than the parent simple Schiff bases. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

3.
The effect of the catalytic moiety on the early‐time photodynamics of Ru/M (M=Pt or Pd) bimetallic photocatalysts is studied by ultrafast transient absorption spectroscopy. In comparison to the Ru/Pd photocatalyst described earlier, the Ru/Pt analogue shows complex excited‐state dynamics with three distinct kinetic components ranging from sub‐ps to 102 ps, requiring a more sophisticated photophysical model than that developed earlier for the Ru/Pd complex. In the Pu/Pt photocatalyst, an additional lower‐lying excited state is proposed to quench the hot higher‐lying triplet metal‐to‐ligand charge‐transfer states. Furthermore, a strong excitation wavelength dependence on the population of excited states is observed for both the Ru/Pt and Ru/Pd complexes, indicating a non‐equilibrated distribution even on the 102 ps timescale. These insights shed light on the significant impact of the catalytic moiety on the fundamental early‐time photophysics of Ru‐based photocatalysts.  相似文献   

4.
A new family of trimetallic complexes of the form [(bpy)2M(phen‐Hbzim‐tpy)M′(tpy‐Hbzim‐phen)M(bpy)2]6+ (M=RuII, Os; M′=FeII, RuII, Os; bpy=2,2′‐bipyridine) derived from heteroditopic phenanthroline–terpyridine bridge 2‐{4‐[2,6‐di(pyridin‐2‐yl) pyridine‐4‐yl]phenyl}‐1H‐imidazole[4,5‐f][1,10]phenanthroline (phen‐Hbzim‐tpy) were prepared and fully characterized. Zn2+ was used to prepare mixed‐metal trimetallic complexes in situ by coordinating with the free tpy site of the monometallic precursors. The complexes show intense absorptions throughout the UV/Vis region and also exhibit luminescence at room temperature. The redox behavior of the compounds is characterized by several metal‐centered reversible oxidation and ligand‐centered reduction processes. Steady‐state and time‐resolved luminescence data show that the potentially luminescent RuII‐ and OsII‐based triplet metal‐to‐ligand charge‐transfer (3MLCT) excited states in the triads are quantitatively quenched, most likely by intercomponent energy transfer to the lower lying 3MLCT (for Ru and Os) or triplet metalcentered (3MC) excited states of the FeII subunit (nonluminescent). Interestingly, iron did not adversely affect the photophysics of the respective systems. This suggests that the multicomponent molecular‐wire‐like complexes investigated here can behave as efficient light‐harvesting antennas, because all the light absorbed by the various subunits is efficiently channeled to the subunit(s) in which the lowest‐energy excited states are located.  相似文献   

5.
A new Azo‐Schiff base ligand L was prepared by reaction of m‐hydroxy benzoic acid with (Schiff base B) of 3‐[2‐(1H–indol‐3‐yl)‐ethylimino]‐1.5‐dimethyl‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐ylamine. This synthesized ligand was used for complexation with different metal ions like Ni(II), Co(II), Pd(II) and Pt(IV) by using a molar ratio of ligand: metal as 1:1. Resulted compounds were characterized by NMR (1H and 13C), UV–vis spectroscopy, TGA, FT‐IR, MS, elemental analysis, magnetic moment and molar conductivity studies. The activation thermodynamic parameters, such as ΔE*, ΔH*, ΔS*, ΔG*and K are calculated from the TGA curves using Coats ‐ Redfern method. Hyper Chem‐8 program has been used to predict structural geometries of compounds in gas phase. The biological activities of Schiff base and its complexes had been tested in vitro against, two Gram positive bacteria (Bacillus subtillis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonas aeruguinosa).  相似文献   

6.
A novel Schiff base compound was synthesized, and its complexation properties with Fe(III) and Cr(III) were investigated. Tripodal ligand was synthesized by the reaction of s‐triazine and 4‐hydroxybenzaldehyde. Then a Schiff base involving 8‐hydroxyquinoline was synthesized by the reaction of 5‐aminomethyl‐8‐hydroxyquinoline ( QN ) and 2,4,6‐tris(p‐formylphenoxy)‐1,3,5‐triazine ( TRIPOD ) in methanol/chloroform media. The obtained Schiff base ( QN-TRIPOD ) was then reacted with four trinuclear Fe(III) and Cr(III) complexes including tetradentate Schiff bases N ,N ′‐bis(salicylidene)ethylenediamine (salenH2)/bis(salicylidene)‐o‐phenylenediamine (SalophenH2). The synthesized ligand and complexes were characterized by means of elemental analysis carrying out 1H NMR, FTIR spectroscopy, thermal analyses, and magnetic susceptibility measurements. Finally, metal ratios of the prepared complexes were determined by using atomic adsorption spectrometry.  相似文献   

7.
Two heterobimetallic Zn‐Nd phenylene‐bridged Schiff‐base ligands complexes [ZnNd L1 (Py)(NO3)3] ( 1 ) and [Zn L2 Nd(Py)(NO3)3]·MeCN ( 2 ) (Py = pyridine, H2L1 = N,N′‐bis‐ (3‐methoxy‐salicylidene)phenylene‐1,2‐diamine, H2L2 = N,N′‐bis‐5‐bromo‐3‐methoxy‐salicylidene)phenylene‐1,2‐diamine) were obtained. Both 1 and 2 were structurally characterized by X‐ray crystallography, and their near‐infrared (NIR) luminescent properties were determined. For the two complexes, the occupation of pyridine at the axial position of 3d Zn2+ ions could effectively prevent luminescent quenching arising from OH‐, NH‐ or CH oscillators of the solvates around the 4f Nd3+ ions, and the heavy‐atom (Br) effect of the Schiff‐base ligands on their NIR luminescent properties is also discussed.  相似文献   

8.
Phosphonio‐benzo[c]phospholides with an additional phosphonium ylide substituent in 3‐position were synthesized by deprotonation of appropriately substituted 1, 3‐bis‐phosphonio benzophospholide cations and characterized by spectroscopic and analytical data. The ability of these molecules to act as bidentate P, C‐chelating ligands to transition metal atoms was demonstrated in the reactions with [W(CO)4(norbornadiene)] and [MCl2(cyclooctadiene)] (M = Pd, Pt). The PdII and PtII complexes are distinguished by a strong inclination towards addition of H2O to the 10π‐electron system of the ligand. The molecular structures of a W0 complex with a P, C‐chelating ylidyl‐phosphonio‐benzophospholide ligand and of the product resulting from H2O‐addition to a corresponding PtII complex were determined. The structural parameters of the W0 complex provide evidence for the presence of substantial steric strain around the metal atom.  相似文献   

9.
The syntheses, crystal structures, and detailed investigations of the photophysical properties of phosphorescent platinum(II) Schiff base complexes are presented. All of these complexes exhibit intense absorption bands with λmax in the range 417–546 nm, which are assigned to states of metal‐to‐ligand charge‐transfer (1MLCT) 1[Pt(5d)→π*(Schiff base)] character mixed with 1[lone pair(phenoxide)→π*(imine)] charge‐transfer character. The platinum(II) Schiff base complexes are thermally stable, with decomposition temperatures up to 495 °C, and show emission λmax at 541–649 nm in acetonitrile, with emission quantum yields up to 0.27. Measurements of the emission decay times in the temperature range from 130 to 1.5 K give total zero‐field splitting parameters of the emitting triplet state of 14–28 cm?1. High‐performance yellow to red organic light‐emitting devices (OLEDs) using these platinum(II) Schiff base complexes have been fabricated with the best efficiency up to 31 cd A?1 and a device lifetime up to 77 000 h at 500 cd m?2.  相似文献   

10.
Phosphorus‐based Schiff base were synthesized by treating bis{3‐[2‐(4‐amino‐1.5‐dimethyl‐2‐phenyl‐pyrazol‐3‐ylideneamino)ethyl]‐indol‐1‐ylmethyl}‐phosphinic acid with paraformaldehyde and characterized as a novel antioxidant. Its corresponding complexes [(VO)2L(SO4)2], [Ni2LCl4], [Co2LCl4], [Cu2LCl4], [Zn2LCl4], [Cd2LCl4], [Hg2LCl4], [Pd2LCl4], and [PtLCl]Cl2 were analyzed by Fourier transform‐infrared, (1H and 13C) nuclear magnetic resonance, and mass and UV–Vis spectroscopy. Experimental data showed that the ligand coordinated with the metal ions via donor atoms such as nitrogen to form an octahedral arrangement of the Schiff base around the central transition‐metal atom. The nature of these complexes was identified using the molar ratio and Job's methods, with the results agreeing with a metal‐to‐ligand (M:L) molar ratio of 2:1, expect for Pt, whose M:L was 1:1. Thermodynamic activation parameters such as ?E*, ?H*, ?S*, ?G*, and K were determined from the thermogravimetric analysis curve using the Coats–Redfern method. The antioxidant activities of the prepared compounds were assessed by using 1.1‐diphenyl‐2‐picrylhydrazyl as the free radical, and the results show that the complex Schiff bases were found to possess potent antioxidant activity. The structure–activity relationship of the ligand and its complexes indicates that the presence of electron‐donating moieties, such as Co(II) and Ni(II), in the chemical structure increases the antioxidant activity, whereas the Pt(IV) and Pd(II) complexes diminished the antioxidant activity, indicating the superior activity of the hydroxyl radical (OH·) over the superoxide radical.  相似文献   

11.
Tri(1‐cyclohepta‐2, 4, 6‐trienyl)phosphane, P(C7H7)3 ([P] when coordinated to a metal atom), was used to stabilize complexes of platinum(II) and palladium(II) with chelating dichalcogenolato ligands as [P]M(E∩E) [E = S, ∩ = CH2CH2, M = Pt ( 3a ); E = S, ∩ = 1, 2‐C6H4, M = Pt ( 5a ), Pd ( 6a ); E = S, ∩ = C(O)C(O), M = Pt ( 7a ), Pd ( 8a ); E = S, Se, ∩ = 1, 2‐C2(B10H10), M = Pt ( 9a, 9b ), Pd ( 10a, 10b ); E = S, ∩ = Fe2(CO)6, M = Pt ( 11a ), Pd ( 12a )]. Starting materials in all reactions were [P]MCl2 with M = Pt ( 1 ) and Pd ( 2 ). Attempts at the synthesis of [P]M(ER)2 with non‐chelating chalcogenolato ligands were not successful. All new complexes were characterized by multinuclear magnetic resonance spectroscopy in solution (1H, 13C, 31P, 77Se and 195Pt NMR), and the molecular structures of 5a and 12a were determined by X‐ray analysis. Both in the solid state and in solution the ligand [P] is linked to the metal atom by the P‐M bond and by η2‐C=C coordination of the central C=C bond of one of the C7H7 rings. In solution, intramolecular exchange between coordinated and non‐coordinated C7H7 rings is observed, the exchange process being markedly faster in the case of M = Pd than for M = Pt.  相似文献   

12.
Homoleptic d8‐metal organothiolates and phenylselenolates [M(EC6H5)2] (E=S, M=Pt 1 , M=Pd 2 , M=Ni 5 ; E=Se, M=Pt 3 , M=Pd 4 ) were prepared as crystalline solids under solvothermal conditions. Their structures were solved using powder X‐ray diffraction data. In each case, the EC6H5 (E=S, Se) ligand binds to two metal ions (M=Pt, Pd, and Ni) to form chain‐like structures with planar (in 1 ) or zig‐zag (in 2 , 3 , 4 , 5 ) conformations. The [M(SR)2] complexes (M=Pt, R=4‐tert‐butylphenyl 6 ; R=2‐naphthyl 8 ; R=4‐nitrophenyl 10 and M=Pd, R=4‐tert‐butylphenyl 7 ; R=2‐naphthyl 9 ; R=4‐nitrophenyl 11 ) were prepared under similar solvothermal conditions. Based on the XPS binding energies and elemental analyses, complexes 6 , 7 , 8 , 9 , 10 , 11 have the same [M(SR)2] formulation as 1 and 2 . The cyclic complex [Pd6(SCH3)12] 12 was prepared as a crystalline solid by solvothermal annealing treatment of the amorphous precipitate. A chain‐like polymer structure is proposed for both [Pd(SC12H25)2] 13 and [Pd(SC16H33)2] 14 ; these polymeric chains self‐assemble to give layer‐like structures. Solid‐state diffuse reflectance spectra reveal that the optical band gap Eg (eV) of complexes 1 , 6 , 8 , 10 and of 2 , 7 , 9 , 11 are in the range of 2.10–3.00 eV and 2.10–2.63 eV, respectively, and 5 has the lowest Eg value (1.72 eV). Heating solid samples of 4 and 13 under solvothermal conditions afforded phase‐pure Pd17Se15 and PdS nanocrystals, respectively. Field‐effect transistors fabricated with a drop‐cast thin film made from Pd17Se15 nanocrystals prior treated with an ethanolic solution of 1‐hexadecanethiol displayed ambipolar charge transporting properties with hole and electron mobility being 7×10?2 cm2 V?1 s?1 and 6×10?2 cm2 V?1 s?1, respectively.  相似文献   

13.
The Schiff base ligand in the title complex, [Pt(C9H8BrN2S2)2], is deprotonated from its tautomeric thiol form and coordinated to PtIIvia the mercapto S and β–N atoms. The configuration about PtII is a perfect square‐planar, with two equivalent Pt—N [2.023 (3) Å] and Pt—S [2.293 (1) Å] bonds. The phenyl ring is twisted against the coordination moiety Pt1/N1/N1′/S2′/S2 by 31.8 (2)°, due to the steric hindrance induced by ortho‐substituted bulky Br atom.  相似文献   

14.
The Schiff base 1‐benzyl‐N ‐(3,5‐di‐tert ‐butylsalicylidene)piperidin‐4‐amine (HL) and its acetatopalladium(II) complex having the formula [Pd(L)(OAc)] were synthesized. Both HL and [Pd(L)(OAc)] were characterized using elemental analysis and various spectroscopic (infrared, UV–visible, 1H NMR and 13C NMR) and mass spectrometric measurements. The molecular structure of the complex was determined using X‐ray crystallographic analysis. In the complex, the pincer‐like NNO‐donor L and the monodenate OAc provide a distorted square‐planar N2O2 coordination environment around the metal centre. The physicochemical properties and the spectroscopic features of [Pd(L)(OAc)] are consistent with its molecular structure. The complex was found to be an effective catalyst for the Suzuki–Miyaura cross‐coupling reactions of hydroxyaryl halides with arylboronic acids in predominantly aqueous media. The reactions afforded hydroxybiaryl products in good to excellent yields with a wide substrate scope.  相似文献   

15.
The interactions of a series of platinum(II) Schiff base complexes with c‐myc G‐quadruplex DNA were studied. Complex [PtL 1a ] ( 1 a ; H2L 1a =N,N′‐bis(salicylidene)‐4,5‐methoxy‐1,2‐phenylenediamine) can moderately inhibit c‐myc gene promoter activity in a cell‐free system through stabilizing the G‐quadruplex structure and can inhibit c‐myc oncogene expression in cultured cells. The interaction between 1 a and G‐quadruplex DNA has been examined by 1H NMR spectroscopy. By using computer‐aided structure‐based drug design for hit‐to‐lead optimization, an in silico G‐quadruplex DNA model has been constructed for docking‐based virtual screening to develop new platinum(II) Schiff base complexes with improved inhibitory activities. Complex [PtL 3 ] ( 3 ; H2L 3 = N,N′‐bis{4‐[1‐(2‐propylpiperidine)oxy]salicylidene}‐4,5‐methoxy‐1,2‐phenylenediamine) has been identified with a top score in the virtual screening. This complex was subsequently prepared and experimentally tested in vitro for its ability to stabilize or induce the formation of the c‐myc G‐quadruplex. The inhibitory activity of 3 (IC50=4.4 μM ) is tenfold more than that of 1 a . The interaction between 1 a or 3 with c‐myc G‐quadruplex DNA has been examined by absorption titration, emission titration, molecular modeling, and NMR titration experiments, thus revealing that both 1 a and 3 bind c‐myc G‐quadruplex DNA through an external end‐stacking mode at the 3’ terminal face of the G‐quadruplex. Such binding of G‐quadruplex DNA with 3 is accompanied by up to an eightfold increase in the intensity of photoluminescence at λmax=652 nm. Complex 3 also effectively down‐regulated the expression of c‐myc in human hepatocarcinoma cells.  相似文献   

16.
Salicylidene Schiff base chelates (R,R)‐(–)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediaminomanganese(III) chloride, (R,R)‐(–)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediaminocobalt(II), N,N′‐bis(salicylidene)‐ethylenediaminocobalt(II), N,N′‐bis(salicylidene)ethylenediaminonickel(II), and N,N′‐bis(salicylidene)ethylenediaminoaquacobalt(II), as well as (R,R)‐(–)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)1,2‐cyclohexanediamine, were kinetically examined as antioxidants in the scavenging of tert‐butylperoxyl radical (tert‐butylOO?). Absolute rate constants and corresponding Arrhenius parameters were determined for reactions of tert‐butylOO? with these chelates in the temperature range ?52.5 to ?11°C. High reactivity of tert‐butylOO? with Mn(III) and Co(II) salicylidene Schiff base chelates was established using a kinetic electron paramagnetic resonance method. These salicylidene Schiff base chelates react in a 1:1 stoichiometric fashion with tert‐butylOO? without free radical formation. Ultraviolet–visible spectrophotometry and differential pulse voltammetry established that the rapid removal rate of tert‐butylOO? by these chelates is the result of Mn(III) oxidation to Mn(IV) and Co(II) oxidation to Co(III) by tert‐butylOO?. It is concluded that removal of alkylperoxyl radical by Mn(III) and Co(II) salicylidene Schiff base chelates may partially account for their biological activities. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 431–439, 2007  相似文献   

17.
Summary The kinetics of the reaction between H2O2 and some Schiff base complexes of MnIII have been investigated in both aqueous and micellar sodium dodecyl sulphate (SDS) solution. The reaction rate is first order in both H2O2 and [complex], and inversely proportional to [H+]. The second-order rate constant increases in the sequence [Mn(salophen)(OAc)] > [Mn(salen)(OH2)]-ClO4 > [Mn(salen)(OAc)]H2O, where salen = N,N-bis-(salicylidene)ethylenediamine and salophen = N,N-bis-(salicylidene)-o-phenylenediamine. At SDS concentrations below the critical micellar concentration, there is almost no effect on the rate of reaction whereas at higher concentrations the reaction rate increases slightly. A mechanism involving MnII and a peroxo intermediate is proposed.  相似文献   

18.
The absorption spectra, luminescence spectra, and luminescence lifetimes of the isomeric [M(bph)(bpy)] and [M(phpy)2] complexes M = Pt(II) or Pd(II), bph2? = 1,1′-biphenyl-2,2′-diyl dianion, phpy? = 2-phenylpyridine-2′-yl anion, and bpy = 2,2′-bipyridine have been investigated and compared with those of [M(bpy)2]2+ complexes and of the free protonated ligands H2bph, Hbpy+, and Hphpy. In the absorption spectra, the region below 320 mm is dominated by ligand-centered (LC) transitions, whereas metal-to-ligand charge transfer (MLCT) transitions are responsible for the bands present in the near UV/VIS region. The MLCT bands move to higher energies on replacing Pt with Pd and in going from [M(bph)(bpy)] to the [M(phpy)2] isomer. For the mixed-ligand complexes, evidence for both M → bph2? (at higher energies) and M → bpy bands is found. The structured luminescence observed at 77 K shows lifetimes of 4.0 and 1.1 μs for [Pt(phpy)2] and [Pt(bph)(bpy)], respectively, and 480 and 250 μs for the analogous Pd complexes. On the basis of the energy and lifetime data, the luminescence of the Pt(II) complexes is assigned to the lowest triplet MLCT excited state, whereas for the Pd complexes the luminescent state is thought to result from a mixture of MLCT and LC triplet levels.  相似文献   

19.
Chiral Half‐sandwich Pentamethylcyclopentadienyl Rhodium(III) and Iridium(III) Complexes with Schiff Bases from Salicylaldehyde and α‐Amino Acid Esters [1] A series of diastereoisomeric half‐sandwich complexes with Schiff bases from salicylaldehyde and L‐α‐amino acid esters including chiral metal atoms, [(η5‐C5H5)(Cl)M(N,O‐Schiff base)], has been obtained from chloro bridged complexes [(η5‐C5Me5)(Cl)M(μ‐Cl)]2 (M = Rh, Ir). Abstraction of chloride from these complexes with Ag[BF4] or Ag[SO3CF3] affords the highly sensitive compounds [(η5‐C5Me5)M(N,O‐Schiff base]+X? (M = Rh, Ir; X = BF4, CF3SO3) to which PPh3 can be added under formation of [(η5‐C5Me5)M(PPh3)(N,O‐Schiff base)]+X?. The diastereoisomeric ratio of the complexes ( 1 ‐ 7 and 11 ‐ 12 ) has been determined from NMR spectra.  相似文献   

20.
A new series of shape‐persistent imine‐bridged macrocycles were synthesized based on dynamic covalent chemistry. The macrocycles had an alternating sequence of dibenzothiophene and N,N′‐bis(salicylidene)‐ethylenediamine (salen) tethering branched alkyl chains. The macrocycles and tetranuclear metallomacrocycles bearing long and branched alkyl chains exhibited thermotropic columnar liquid‐crystalline phases over a wide temperature range and the metallomacrocycles greatly depended on the characteristics of the coordinated metal ions. The metal‐free macrocycle showed a liquid‐crystalline phase with a lamellar structure and poor birefringence. In sharp contrast, the macrocyclic Ni complex showed a columnar oblique liquid‐crystalline phase, whereas the Pd and Cu complexes showed columnar liquid‐crystalline phases with a lamellar structure. The macroscopic organization and thermal properties of the corresponding liquid‐crystalline metallomacrocycles were significantly dependent on the subtle structural differences among the planar macrocycles, which were revealed by single‐crystal X‐ray crystallographic analysis of the macrocycles with shorter alkyl chains.  相似文献   

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