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991.
Three lanthanide‐based two‐dimensional (2D) coordination polymers (CPs), [Ln(L)(H2O)2]n, {H3L=(HO)2P(O)CH2CO2H; Ln=Dy3+ (CP 1 ), Er3+ (CP 2 )} and [{Gd2(L)2(H2O)3}.H2O]n, (CP 3 ) were hydrothermally synthesized using phosphonoacetic acid as a linker. Structural features revealed that the dinuclear Ln3+ nodes were present in the 2D sheet of CP 1 and CP 2 while in the case of CP 3 , nodes were further connected to each other forming a chain‐type arrangement throughout the network. The magnetic studies show field‐induced slow magnetic relaxation property in CP 1 and CP 2 with Ueff values of 72 K (relaxation time, τ0=3.05×10?7 s) and 38.42 K (relaxation time, τ0=4.60×10?8 s) respectively. Ab‐initio calculations suggest that the g tensor of Kramers doublet of the lanthanide ion (Dy3+ and Er3+) is strongly axial in nature which reflects in the slow magnetic relaxation behavior of both CPs. CP 3 exhibits a significant magnetocaloric effect with ?ΔSm=49.29 J kg?1 K?1, one of the highest value among the reported 2D CPs. Moreover, impedance analysis of all the CPs show high proton conductivity with values of 1.13×10?6 S cm?1, 2.73×10?3 S cm?1 and 2, 6.27×10?6 S cm?1 for CPs 1 – 3 , respectively, at high temperature (>75 °C) and maximum 95 % relative humidity (RH). 相似文献
992.
Waqas Jamil Sorath Solangi Muhammad Ali Khalid Muhammad Khan Muhammad Taha Muhammad Yar Khuhawar 《Arabian Journal of Chemistry》2019,12(8):2262-2269
2-Hydroxy salicylhydrazide isatin hydrazone (L) and its Mn (II), Co (II), Ni (II), Cu (II), and Zn (II), metal complexes were synthesized. 1H NMR, UV–Vis, IR spectroscopy and elemental (CHN/S) analysis techniques were applied for characterization. TG/DTA techniques revealed that all the synthetic compounds are thermally stable up to 300 °C. They were found non-electrolytes in nature. Furthermore, all these complexes were evaluated for antiglycation and DPPH radical scavenging activities. They showed varying degree of activity with IC50 values between 168.23 and 269.0 μM in antiglycation and 29.63–57.71 μM in DPPH radical scavenging activity. Mn (II), Co (II), Ni (II), Cu (II), and Zn (II), metal complexes showed good antiglycation as well as DPPH radical scavenging activity. The IC50 values for antiglycation activity are 168.23 ± 2.37, 234.27 ± 4.33, 257.1 ± 6.43, 267.7 ± 8.43, 269.0 ± 8.56 Ni for Co, Zn, Mn, Cu, and Ni complexes, respectively, while IC50 value were found to be 29.63 ± 2.76, 31.13 ± 1.41, 35.16 ± 2.45, 43.53 ± 3.12, 57.71 ± 2.61 μM for Cu, Zn, Mn, Co and Ni complexes, respectively, for DPPH radical scavenging activity. These synthesized metal complexes were found to be better active than standards Rutin (IC50 = 294.46 μM) for anti-glycation, and tert-butyl-4-hydroxyanisole (IC50 = 44.7 μM) for DPPH radical scavenging activity. 相似文献
993.
《Arabian Journal of Chemistry》2019,12(8):2476-2483
The reaction kinetics of 4,6-dinitrobenzofuroxan with five heterocyclic amines was investigated spectrophotometrically (UV–Vis) in acetonitrile at 20 °C. It was observed that the rate constants of these reactions increased as follows: 2-aminopyrimidine > 2-aminothiazole > 2-aminobenzothiazole > 5-amino-3,4-dimethylisoxazole > 2-amino-5-trifluoromethyl-1,3,4-thiadiazole. Further, second-order rate constants (k1) pertaining to the C–N and C–C bond forming step of these complexation processes fit to the three parameter equation log k (20 °C) = sN (N + E), allowing the determination of the nucleophilicity parameters (N) of the five heterocyclic amines. The heterocyclic amines were subsequently ranked on the comprehensive nucleophilicity scale defined by Mayr et al. (2003), providing a direct comparison of n-, π-, and σ-nucleophiles. 相似文献
994.
Yanyan An Liping Lu Miaoli Zhu 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(9):1286-1298
Coordination polymers (CPs) with specific structures and functional luminescence have been widely designed as sensors for detecting small molecules and ions. In this study, with or without the help of an N‐donor auxiliary linker, three new ZnII CPs, namely, three‐dimensional (3D) poly[[pentaaquabis[μ3‐5‐(4‐carboxybenzyloxy)isophthalato]bis[μ6‐5‐(4‐carboxylatobenzyloxy)isophthalato]di‐μ3‐hydroxido‐hexazinc(II)] trihydrate], {[Zn6(C16H10O7)2(C16H9O7)2(OH)2(H2O)5]·3H2O}n or {[Zn6(μ3‐HL)2(μ6‐L)2(μ3‐OH)2(H2O)5]·3H2O}n, ( I ), one‐dimensional (1D) catena‐poly[[[aqua(1,10‐phenanthroline)zinc(II)]‐μ2‐5‐(4‐carboxybenzyloxy)isophthalato] dihydrate], {[Zn(C16H10O7)(C12H8N2)(H2O)]·2H2O}n or {[Zn(μ2‐HL)(phen)(H2O)]·2H2O}n (phen is 1,10‐phenanthroline), ( II ), and 3D poly[diaquatetrakis(4,4′‐bipyridine)bis[μ6‐5‐(4‐carboxylatobenzyloxy)isophthalato]di‐μ3‐formato‐di‐μ3‐hydroxido‐pentazinc(II)], [Zn5(C16H9O7)2(HCOO)2(OH)2(C10H8N2)4(H2O)2]n or [Zn5(μ4‐L)2(bpy)4(μ2‐OH)2(μ3‐HCOO)2(H2O)2]n (bpy is 4,4′‐bipyridine), ( III ), have been constructed from the semi‐rigid tricarboxylic acid 5‐(4‐carboxybenzyloxy)isophthalic acid (H3L) under hydrothermal conditions. CP ( I ) exhibits a twofold interpenetrated 3D+3D→3D skeleton with a 3 , 5 ‐conn topology constructed from triangular trinuclear [Zn3(COO)4(μ3‐OH)] clusters, in which the H3L ligand adopts three different coordination modes. CP ( II ) exhibits a 1D infinite chain and stacking that gives a 3D structure mediated by hydrogen bonds and weak interactions. CP ( III ) is an interesting 3D 3 , 4 , 8 ‐conn network including linear tetranuclear [Zn4(μ2‐OH)2(HCOO)2(COO)2] clusters with a new {4·62}2{4·64·8}{46·619·83} topological symbol. The influences of the flexible –CH2–O– linker of the H3L ligand and subtle environmental factors, such as solvent, pH value and auxiliary ligands, on the formation of the final structures are also discussed. The solid‐state fluorescence spectra of CPs ( I )–( III ) were recorded at room temperature and all show better fluorescence performances than H3L. In particular, ( II ) can act as a potential multifunctional fluorescent material for sensing hexavalent chromium ions in aqueous solution with high stability, selectivity and sensitivity. Under ultraviolet light of 365 nm from a UV lamp, a signal response of fluorescence from turning on to off can be observed with the naked eye. It was found that the detection for hexavalent chromium (i.e. Cr2O72?) by ( II ) has a high selectivity [KSV = 1.61 × 104M?1 and limit of detection (LOD) = 0.434 µM] in aqueous solution. Quenching mechanisms were also studied in detail. 相似文献
995.
Guo-Xia Jin Tian-Chao You Jian-Ping Ma 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(12):1690-1697
The new asymmetrical organic ligand 2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole ( L , C17H13N5O), containing pyridine and imidazole terminal groups, as well as potential oxdiazole coordination sites, was designed and synthesized. The coordination chemistry of L with soft AgI, CuI and CdII metal ions was investigated and three new coordination polymers (CPs), namely, catena‐poly[[silver(I)‐μ‐2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole] hexafluoridophosphate], {[Ag( L )]PF6}n, catena‐poly[[copper(I)‐di‐μ‐iodido‐copper(I)‐bis(μ‐2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole)] 1,4‐dioxane monosolvate], {[Cu2I2( L )2]·C4H8O2}n, and catena‐poly[[[dinitratocopper(II)]‐bis(μ‐2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole)]–methanol–water (1/1/0.65)], {[Cd( L )2(NO3)2]·2CH4O·0.65H2O}n, were obtained. The experimental results show that ligand L coordinates easily with linear AgI, tetrahedral CuI and octahedral CdII metal atoms to form one‐dimensional polymeric structures. The intermediate oxadiazole ring does not participate in the coordination interactions with the metal ions. In all three CPs, weak π–π interactions between the nearly coplanar pyridine, oxadiazole and benzene rings play an important role in the packing of the polymeric chains. 相似文献
996.
基于有机-无机杂化材料的理念,利用稀土硝酸铽[Tb(NO3)3]、有机配体BINDI (BINDI=N,N′-双(5-间苯二甲酸)-1,4,5,8-萘二酰亚胺)及Keggin型多酸H4SiW12O40·26H2O在溶剂热的条件下反应,成功合成出多酸基稀土配位聚合物Tb4[SiW12O40]·[BINDI)]2·[DMA]16。采用X-射线单晶衍射仪、X-射线粉末衍射仪、红外光谱仪、热重分析仪、紫外-可见吸收光谱仪、元素分析仪、荧光光谱仪和电子顺磁共振仪对稀土聚合物的结构组成、热稳定性、发光性能以及光致变色性能进行了表征。X-射线单晶衍射分析发现该稀土配位聚合物结晶于Tetragonal晶系,空间群为P42/n,展现出3D手性双螺旋网络结构特征,其中多酸阴离子SiW12O40(简写为{SiW12})镶嵌在稀土有机基团形成的孔道中;红外及紫外吸收光谱分析发现稀土Tb3+与配体(BINDI)配位成键;荧光光谱表明,在380 nm的激发波长下,配体显示出最强荧光发射峰,位于441 nm处,而化合物的最强发射峰位于471 nm处。由于三价铽离子不易被氧化也很难被还原,所以化合物的荧光发射不能归因于金属与配体之间的电子辐射跃迁,且化合物的发射峰与配体的发射峰比较相近,因此荧光主要是配体BINDI的发光。另外Tb(Ⅲ)离子的特殊跃迁发射带没有出现是因为在荧光测试时由于光照的原因导致样品的颜色发生了突变,即发生了光致变色的现象,导致光诱导电子转移以致荧光猝灭。引起金属配合物荧光猝灭的原因通常是光致电子转移,而电子转移的方向是配体中的电子向金属空轨道转移(LMCT)所致,形成配合物后其最大发射峰红移或蓝移是由电子转移导致分子内电子分布的改变,从而引起HOMO-LUMO能隙的减小或增大所致,与配体荧光光谱相比,化合物的发射峰发生了红移。此外,电子顺磁共振结果表明由于化合物中的BINDI配体在紫外与可见光照射下发生电子转移形成配体自由基,以及多酸在光激发下,发生W5+→W6+的过程进一步促进该化合物发生光致变色现象。因此,该化合物具有极其敏锐光致变色的性质。 相似文献
997.
998.
Manuela Chiper David Fournier Richard Hoogenboom Ulrich S. Schubert 《Macromolecular rapid communications》2008,29(20):1640-1647
Metallo‐supramolecular polymers offer attractive possibilities to combine the properties of polymers with the characteristics offered by the metal–ligand coordination. Here we present for the first time the combination of metal‐bis(terpyridine) complexes and lower critical solution temperature (LCST) polymers that can be switched by addressing either the thermosensitive polymer or the metal complex. We describe a new strategy for the synthesis of poly(N‐isopropylacrylamide) (PNIPAM) end functionalized with a terpyridine moiety, which is further used for the preparation of FeII and ZnII‐bis(terpyridine PNIPAM). The comparison of the LCST behavior of the uncomplexed ligands and their metal complexes that bear different counter ions is included. Furthermore, the switchability of the synthesized FeII system is demonstrated by a decomplexation reaction followed by the characterization of the uncomplexed ligand.
999.
ukasz Orze Maria Oszajca Justyna Polaczek Dominika Porbska Rudi van Eldik Grayna Stochel 《Molecules (Basel, Switzerland)》2021,26(16)
Pressure is one of the most important parameters controlling the kinetics of chemical reactions. The ability to combine high-pressure techniques with time-resolved spectroscopy has provided a powerful tool in the study of reaction mechanisms. This review is focused on the supporting role of high-pressure kinetic and spectroscopic methods in the exploration of nitric oxide bioinorganic chemistry. Nitric oxide and other reactive nitrogen species (RNS) are important biological mediators involved in both physiological and pathological processes. Understanding molecular mechanisms of their interactions with redox-active metal/non-metal centers in biological targets, such as cofactors, prosthetic groups, and proteins, is crucial for the improved therapy of various diseases. The present review is an attempt to demonstrate how the application of high-pressure kinetic and spectroscopic methods can add additional information, thus enabling the mechanistic interpretation of various NO bioinorganic reactions. 相似文献
1000.
光催化具有无污染、安全高效等优点,已成为环保领域的研究热点。 本文选择2,4-二(3,5-二甲基吡唑)-6-二乙基胺-1,3,5-三嗪(L1)和2, 6-二[3-(5-甲基吡唑基)]吡啶(L2)为配体、以RuCl3为金属源,合成了3种配合物[Ru(L1)Cl3](1)、[Ru(L2)2]·Cl3(2)和[Ru(L2)2]·(H2BTC)·(HBTC)·H2O(3),同时进行了IR、UV-Vis、TG及X射线衍射等表征,并对配合物在光催化降解罗丹明B方面进行了探讨,结果表明,配合物13均具有一定程度的光降解效果,降解效果分别为46.8%、44.7%和40.4%。 相同条件下,加入H2O2后的配合物13的降解效果比金属盐、配体及H2O2单独存在时的降解效果好。 相似文献