共查询到20条相似文献,搜索用时 15 毫秒
1.
Larsen J Brüggemann B Khoury T Sly J Crossley MJ Sundström V Akesson E 《The journal of physical chemistry. A》2007,111(42):10589-10597
We report on a study of singlet-singlet annihilation kinetics in a series of Zn(II)-porphyrin-appended dendrimers, where the energy transfer efficiency is significantly improved by extending the molecular chain that connects the light-harvesting chromophores to the dendrimeric backbone with one additional carbon. For the largest dendrimer having 64 Zn(II)-porphyrins, only approximately 10% of the excitation intensity is needed in order to observe the same extent of annihilation in the dendrimers with the additional carbon in the connecting chain as compared to those without. Complete annihilation, until only one chromophore remains excited, now occurs within subunits of seven chromophores, when half of the chromophores are excited. The improvement of the annihilation efficiency in the largest dendrimer with 64 porphyrins can be explained by the presence of a the two-step delayed annihilation process, involving energy hopping from excited to nonexcited chromophores prior to annihilation. In the smallest dendrimer with only four chromophores, delayed annihilation is not present, since the direct annihilation process is more efficient than the two-step delayed annihilation process. As the dendrimer size increases and the chances of originally exciting two neighboring chromophores decreases, the delayed annihilation process becomes more visible. The additional carbon, added to the connecting chain, results in more favorable chromophore distances and orientations for energy hopping. Hence, the improved energy transfer properties makes the Zn(II)-porphyrin-appended dendrimers with the additional carbon promising candidates as light-harvesting antennas for artificial photosynthesis. 相似文献
2.
Giribabu L Bessho T Srinivasu M Vijaykumar C Soujanya Y Reddy VG Reddy PY Yum JH Grätzel M Nazeeruddin MK 《Dalton transactions (Cambridge, England : 2003)》2011,40(17):4497-4504
Two new heteroleptic ruthenium(II) photosensitizers that contains 2,2';6,2'-terpyridine with extended π-conjugation with donor groups, a 4,4'-dicarboxylic acid-2,2'-bipyridine anchoring ligand and a thiocyanate ligand have been designed, synthesized and fully characterized by CHN, mass spectrometry, UV-vis and fluorescence spectroscopies and cyclic voltammetry. The new sensitizers have either 3,5-di-tert-butyl phenyl (m-BL-5) or triphenylamine (m-BL-6) groups, where the molar extinction coefficient of both the sensitizers is higher than the analogous ruthenium dyes. Both the sensitizers were tested in dye-sensitized solar cells using two different redox electrolytes. 相似文献
3.
Aratani N Cho HS Ahn TK Cho S Kim D Sumi H Osuka A 《Journal of the American Chemical Society》2003,125(32):9668-9681
Electronically coupled porphyrin arrays are suitable for artificial light harvesting antenna in light of a large absorption cross-section and fast excitation energy transfer (EET). Along this line, an artificial energy transfer model system has been synthesized, comprising of an energy donating meso-meso linked Zn(II) porphyrin array and an energy accepting 5,15-bisphenylethynylated Zn(II) porphyrin linked via a 1,4-phenylene spacer. This includes an increasing number of porphyrins in the meso-meso linked Zn(II) porphyrin array, 1, 2, 3, 6, 12, and 24 (Z1A, Z2A, Z3A, Z6A, Z12A, and Z24A). The intramolecular singlet-singlet EET processes have been examined by means of the steady-state and time-resolved spectroscopic techniques. The steady-state fluorescence comes only from the acceptor moiety in Z1A-Z12A, indicating nearly the quantitative EET. In Z24A that has a molecular length of ca. 217 A, the fluorescence comes largely from the acceptor moiety but partly from the long donor array, indicating that the intramolecular EET is not quantitative. The transient absorption spectroscopy has provided the EET rates in real time scale: (2.5 ps)(-1) for Z1A, (3.3 ps)(-1) for Z2A, (5.5 ps)(-1) for Z3A, (21 ps)(-1) for Z6A, (63 ps)(-1) for Z12A, and (108 ps)(-1) for Z24A. These results have been well explained by a revised F?rster equation (Sumi formula), which takes into account an exciton extending coherently over several porphyrin pigments in the donor array, whose length is not much shorter than the average donor-acceptor distance. Advantages of such strongly coupled porphyrin arrays in light harvesting and transmission are emphasized in terms of fast EET and a large absorption cross-section for incident light. 相似文献
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5.
By utilizing energy transfer from ligands to metal ions, efficient white-light-emission (ΦPL: 0.54, x?=?0.31, y?=?0.33) was realized in a heterometallo-supramolecular polymer with Eu(III) and Zn(II) ions introduced alternately. The polymer showed strong white-light-emission even in the film state as well as in solution. 相似文献
6.
The composition and stability constants of the complexes formed between Ni(2+) and Zn(2+) and 3-mercaptopropionic acid (3-MPA) were studied by a potentiometric method at 25 degrees and in 0.5M KNO(3). For the system Zn(2+)/3-MPA. a mixture of the mononuclear complex BA(2) and the polynuclear complexes B(3)A(4). and B(4)A(6) was found (B means the metal ion and A the ligand). The system Ni(2+)/3-MPA can be represented by the complexes B(5)A(10), B(6)A(11) B(6)A(9) and B(6)A(12). In this series the last two complexes are predominant. 相似文献
7.
Cadranel A Alborés P Yamazaki S Kleiman VD Baraldo LM 《Dalton transactions (Cambridge, England : 2003)》2012,41(17):5343-5350
We report the synthesis, structure and properties of the cyanide-bridged dinuclear complex ions [Ru(L)(bpy)(μ-NC)M(CN)(5)](2-/-) (L = tpy, 2,2';6',2'-terpyridine, or tpm, tris(1-pyrazolyl)methane, bpy = 2,2'-bipyridine, M = Fe(II), Fe(III), Cr(III)) and the related monomers [Ru(L)(bpy)X](2+) (X = CN(-) and NCS(-)). All the monomeric compounds are weak MLCT emitters (λ = 650-715 nm, ? ≈ 10(-4)). In the Fe(II) and Cr(III) dinuclear systems, the cyanide bridge promotes efficient energy transfer between the Ru-centered MLCT state and a Fe(II)- or Cr(III)-centered d-d state, which results either in a complete quenching of luminescence or in a narrow red emission (λ ≈ 820 nm, ? ≈ 10(-3)) respectively. In the case of Fe(III) dinuclear systems, an electron transfer quenching process is also likely to occur. 相似文献
8.
Bazzicalupi C Biagini S Bianchi A Faggi E Gratteri P Mariani P Pina F Valtancoli B 《Dalton transactions (Cambridge, England : 2003)》2010,39(42):10128-10136
The new macrocyclic ligand 1,9(4,7)-diphenanthroline-3,7,11,15-tetraazacyclohexadecaphane (L) was synthesized by a 2?:?2 reaction of 1,10-phenanthroline-4,7-dialdehyde with 1,3-diaminopropane, followed by reduction with NaBH(4). L contains two phenanthroline groups linked together by two 1,3-diaminopropane chains in such a way that the heteroaromatic nitrogen atoms point outside the ligand cavity. The ligand structure defines two pairs of identical compartments displaying a specific ability in the binding of protons (1,3-diaminopropane) and metal ions (phenanthroline). Protonation and Zn(II) coordination were studied by means of potentiometric and spectroscopic ((1)H NMR, UV-vis, fluorescence) techniques. Both protonation and Zn(II) coordination consistently affect the fluorescence emission properties of L, giving rise to enhancement or quenching of the emission, depending on the species involved. L becomes emissive upon protonation, but the formation of the highly protonated species, in particular the fully protonated [H(6)L](6+), quenches the emission. The mono- and dinuclear Zn(II) complexes of the unprotonated ligand are non-emissive, like free L, while Zn(II) binding to [HL](+) activates the emission. The most interesting aspect, however, is the chelation enhancement of quenching (CHEQ) observed upon Zn(II) binding to [H(2)L](2+) and [H(4)L](4+), being among the few examples of CHEQ effect observed for Zn(II) complexes. Hydrogen bonding between a metal coordinated water molecule and a phenanthroline group seems to be responsible for the CHEQ observed for [ZnH(2)L](4+). 相似文献
9.
Agnieszka Jabłońska-Wawrzycka Barbara Barszcz Katarzyna Stadnicka 《Journal of Thermal Analysis and Calorimetry》2010,101(2):463-469
For a comparison of structural data and thermal behaviour of Zn(II) and Cd(II) complexes with biologically important ligand,
2-hydroxymethylbenzimidazole (L) the complex of the formula [ZnL3](NO3)2L0.67L′0.33 was prepared and characterized by elemental analysis, infrared (IR) spectra, single-crystal X-ray diffraction and thermal
analysis (where L′ = 2-carbaldehydebenzimidazole). IR and X-ray studies have confirmed a bidentate fashion of coordination
of the 2-hydroxymethylbenzimidazole to Zn(II) ion (through the nitrogen atom of heteroaromatic ring and oxygen atom of hydroxymethyl
group). The zinc ion is hexacoordinated and the shape of polyhedron can be described as pseudo-octahedron (N3O3 chromophore type). The decomposition process of studied Zn(II) and Cd(II) benzimidazole complexes in the air atmosphere proceeds
in three or four main stages and traces structures of complexes. On the basis of the first DTGmax of the decompositions the thermal stability of the complexes follows the order: [CdL3](NO3)2LEtOH0.25 < [CdL2(NO3)2] < [ZnL3](NO3)2L0.67L′0.33. As the final solid products of thermal decomposition suitable metal oxides are formed. 相似文献
10.
The thermal decompositions of crystalline Co(II), Ni(II) and Zn(II) complexes with thiosalicylic acid or ethylenediamine were investigated via the respective thermal curves. On the basis of the decomposition temperatures, the following sequences of stabilities of the studied compounds have been proposed: 1. [Co(SR)][Ni(SR)]<[Zn(SR)]; 2. [Zn(en)2](NO3)2·2H2O<[Co(en)2](NO3)2<[Ni(en)3](NO3)2. 相似文献
11.
A novel fluorescent chemosensor with two 5-nitro-salicylaldehyde groups at the upper rim of calix[4]arene has been synthesized. The chemosensor can effectively recognize copper(II) ion. This system could be considered as a molecular switch. By alternating the light irradiation of mixed solution formed by the host and Cu2+, off-on-off fluorescent switching is carried out. 相似文献
12.
Maria T. Moreno Rafael Rodríguez-Amaro Jose M. Rodríguez Mellado Manuel Mayén Francisco Jiménez Guardeño 《Comptes Rendus Chimie》2018,21(9):884-889
Imidazolinone and triazine herbicides are used in many countries and may have a great impact on metal biocycles in soil. This article deals with the dynamics of imidazolinone and triazine herbicides in soils related to the formation of complexes with Cu(II) ions, which can be very stable. The stability constants of the complexes formed by five imidazolinone herbicides and ten triazine herbicides with Cu(II) ions are determined by means of fast, easy, and inexpensive measurements performed by ultraviolet–visible spectroscopy, for imidazolinones, and voltammetry (cyclic and differential pulse), for triazines. Because of the occurrence of dissociation reactions, the determinations were performed at three pH values for imidazolinones and at one pH value for triazines. In aqueous solutions of 5 < pH < 10 (corresponding to the majority of soils of agricultural use), the herbicides form very stable complexes with the Cu(II) ions, the complexes being integrated by two ligands (herbicides) and one copper ion. In conclusion, crops treated with such herbicides in conjunction with Cu(II) salts experience a decrease in its persistence and effectiveness. In addition, the herbicides and the copper ions may pass to the phreatic layer of the soil, increasing the chance of pollution. 相似文献
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Baron A Herrero C Quaranta A Charlot MF Leibl W Vauzeilles B Aukauloo A 《Chemical communications (Cambridge, England)》2011,47(39):11011-11013
Spectroscopic, electrochemical and theoretical characterisations of photoactive systems readily assembled via click-chemistry show an efficient bi-directional charge shift through the triazole link. 相似文献
15.
Vithaya Ruangpornvisuti Kirawit Supakornchailert Chumnan Tungchitpienchai Banchob Wanno 《Structural chemistry》2006,17(1):27-34
The structure optimizations of 2-formylpyridine (H2FoPyS), 3-formylpyridine (H3FoPyS), and 4-formylpyridine (H4FoPyS) semicarbazone complexes with Co(II), Ni(II), and Zn(II) were carried out using DFT calculations at the B3LYP/LANL2DZ level of theory. The B3LYP/LANL2DZ-optimized geometry parameters for the H2FoPyS and H3FoPyS complexes show good agreement with their corresponding X-ray crystallographic data. Due to the X-ray crystallographic structures of the [Zn(H3FoPyS)2]2+ complex and the H4FoPyS complexes with Co(II), Ni(II), and Zn(II) and have not yet been observed, their B3LYP/LANL2DZ-optimized structures are therefore theoretically proposed. The reaction energies and thermodynamic properties of complexation for these complexes computed at the same level of theory are reported. 相似文献
16.
The complexes of the dithiophosphinic acids with Pd(II), Pb(II), Cd(II), and ZN(II) in a toluene-ethanol medium produce single polarographic waves. The half-wave potential is a linear function of the ligand concentration. The stabilities of these chelates, which are characterized by a sulphur-metal bond, are in the order: Pd(II) > Pb(II) > Cd(II) > Zn(II). 相似文献
17.
Matthews CJ Thompson LK Parsons SR Xu Z Miller DO Heath SL 《Inorganic chemistry》2001,40(17):4448-4454
A series of trigonal bipyramidal pentanuclear complexes involving the alkoxo-diazine ligands poap and p3oap, containing the M(5)[mu-O](6) core is described, which form by a strict self-assembly process. [Co(5)(poap-H)(6)](ClO(4))(4).3H(2)O (1), [Mn(5)(poap-H)(6)](ClO(4))(4).3.5CH(3)OH.H(2)O (2), [Mn(5)(p3oap-H)(6)](ClO(4))(4).CH(3)CH(2)OH.3H(2)O (3), and [Zn(5)(poap-H)(6)](ClO(4))(4).2.5H(2)O (4) are homoleptic pentanuclear complexes, where there is an exact match between the coordination requirements of the five metal ions in the cluster, and the available coordination pockets in the polytopic ligand. [Zn(4)(poap)(poap-H)(3)(H(2)O)(4)] (NO(3))(5).1.5H(2)O (5) is a square [2 x 2] grid with a Zn(4)[mu-O](4) core, and appears to result from the presence of NO(3), which is thought to be a competing ligand in the self-assembly. X-ray structures are reported for 1, 4, and 5. 1 crystallized in the monoclinic system, space group P2(1)/n with a = 13.385(1) A, b = 25.797(2) A, c = 28.513(3) A, beta = 98.704(2) degrees, and Z = 4. 4 crystallized in the triclinic system, space group P1 with a = 13.0897(9) A, b = 18.889(1) A, c = 20.506(2) A, alpha = 87.116(1) degrees, beta = 74.280(2) degrees, gamma = 75.809(2) degrees, and Z = 2. 5 crystallized in the monoclinic system, space group P2(1)/n with a = 14.8222(7) A, b = 21.408(1) A, c = 21.6197(9) A, beta = 90.698(1) degrees, and Z = 4. Compounds 1-3 exhibit intramolecular antiferromagnetic coupling. 相似文献
18.
C. M. Pereira N. Tirilly M. C. Martins F. Silva 《Analytical and bioanalytical chemistry》2001,369(7-8):609-612
Square-wave voltammetry (SWV) has been used to study the transfer of zinc(II) ion under static conditions, assisted by 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine (DPT), through gel-supported microinterfaces. Microhole arrays created by laser photoablation of thin polyester films were used to support an organic gel phase prepared by addition of 1,3?:?2,4-dibenzylidenesorbitol (DBS) to a solution of o-nitrophenyloctyl ether (o-NPOE) with the appropriate supporting electrolyte. The results show that SWV can be used with the gel-supported microinterfaces if a gelified aqueous reference is used for the organic phase. Under such conditions a preliminary estimate of the detection limit for the determination of Zn2+ is 5 × 10–8 mol L–1. 相似文献
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20.
D. Czakis-Sulikowska J. Radwańnska-Doczekalska M. Markiewicz M. Pietrzak 《Journal of Thermal Analysis and Calorimetry》2008,93(3):789-794
New mixed ligand complexes of the following stoichiometric formulae: M(2-bpy)2(RCOO)2·nH2O, M(4-bpy)(RCOO)2·H2O and M(2,4’-bpy)2(RCOO)2·H2O (where M(II)=Zn, Cd; 2-bpy=2,2’-bipyridine, 4-bpy=4,4′-bipyridine, 2,4′-bpy=2,4′-bipyridine; R=C2H5; n=2 or 4) were prepared in pure solid-state. These complexes were characterized by chemical and elemental analysis, IR and
conductivity studies.
Thermal behaviour of compounds was studied by means of DTA, DTG, TG techniques under static conditions in air. The final products
of pyrolysis of Cd(II) and Zn(II) compounds were metal oxides MO. A coupled TG/MS system was used to analyse of principal
volatile products of thermal decomposition or fragmentation of Zn(4-bpy)(RCOO)2·H2O under dynamic air and argon atmosphere.
The principal species correspond to: C+, CH+, CH3
+, C2H2
+, HCN+, C2H5
+ or CHO+, CH2O+ or NO+, CO2
+, 13C16O2
+ and 12C16O18O+ and others; additionally CO+ in argon atmosphere. 相似文献