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1.
采用密度泛函理论(DFT)对钌掺杂的铂团簇阳离子([PtnRum]+, m + n = 3, n ≥ 1)活化甲醇C―H和O―H键反应进行了理论研究;探讨了电荷对[PtnRum]团簇反应活性的影响。电荷分析表明:(1) [Pt3]+团簇中正电荷在三个Pt原子上均匀分布;掺杂Ru原子后,正电荷主要分布在Ru原子上; (2)首先活化C―H键时[PtnRum]+的反应活性比[PtnRum]明显提高;首先活化O―H键时只有[Pt3]+比[Pt3]团簇的反应活性有明显提高。本研究可为金属团簇调控的C―H键和O―H键的活化提供更深入的理解。  相似文献   

2.
磷键作为一种新型的分子键合力,因在晶体工程和超分子合成等方面的重要作用而越来越多地引起科研工作者的广泛关注。本文采用量子化学从头算和电子密度拓扑分析等方法,在MP2/aug-cc-pVTZ理论水平上,对PO2X…PX3和PO2X…PH2X (X = F, Cl, Br, CH3, NH2) π型复合物的结构和磷键性质进行了理论研究。研究表明:π-hole磷键复合物存在A和B两种稳定构型,分别以P…P和P…X磷键作用为主。分子中原子(AIM)、非共价作用(NCI)、电子定域函数(ELF)及适应性自然密度划分(AdNDP)分析表明,不同取代基对该类磷键作用的性质产生很大影响:当取代基为给电子基(CH3, NH2)时,磷键具有明显的共价作用特征;当取代基为吸电子基(F, Cl, Br)时,构型和取代基不同的磷键分别表现为非共价、部分共价或共价作用特征。自然键轨道(NBO)分析指出,分子间磷键的Wiberg键级的数值越大,磷键的共价性越强,磷键的作用强度越大。构型B的电荷转移主要是PX3/PH2X中X原子上的孤对电子转移到PO2X中π*(P=O)反键空轨道。  相似文献   

3.
李文杰  田东旭  杜红  燕希强 《电化学》2021,27(4):357-365
燃料电池的阴极反应的反应动力学速率非常慢,限制了燃料电池技术的发展。因此,寻找低成本、高活性的氧还原催化剂具有重要的意义。多元金属核壳团簇表现出优良的氧还原活性。在本文中,以原子个数为19、38、55和79的八面体团簇作催化剂模型,采用密度泛函理论(GGA-PBE-PAW)方法,研究了一系列不同尺寸核壳Nim@Mn-m (n = 19, 38, 55, 79;m = 1, 6, 13, 19; M = Pt, Pd, Cu, Au, Ag)团簇催化剂的活性规律。优化*O、*OH和*OOH吸附中间体结构,计算了吸附自由能和反应吉布斯自由能,以超电势为催化活性的描述符,研究了单原子Pt嵌入Nim@Aun-m团簇的活性规律。结果表明,Ni6@Pt1Au31具有最好的ORR活性,并且Ni1@Pt1Au17、Ni6@Pt1Au31、Ni13@Pt1Au41、Ni19@Pt1Au5表现出比Pt38团簇以及Pt(111)表面更高的催化活性。Bader电荷和态密度分析表面,核壳之间的电荷转移以及单原子Pt嵌入Nim@Aun-m表面,改变了吸附位的电子性质,降低了*OH的吸附强度,提高了ORR活性。单原子Pt嵌入Nim@Aun-m表面可能是一种合适的多元金属核壳ORR催化剂设计策略。  相似文献   

4.
李海茹  张层  李思殿 《化学学报》2022,80(7):888-895
基于第一性原理, 系统地研究了Ben (n=1~3)对B12团簇结构的调控. 结果表明: 团簇BeB12全局极小结构为Cs对称性准平面结构, 而Be2B12和Be3B12最稳定的结构均为笼状结构, 对称性分别为CsC2v. 随着Ben (n=1~3)原子数的增加, 团簇B12由准平面结构过渡到笼状结构, 且Be倾向内嵌在B12笼状结构表面的B7或B8单元环中, 通过离子和共价作用形成稳定Be&B7和Be&B8单元, 从而稳定笼状结构. 自然键轨道(NBO)分析表明, 团簇Cs BeB12, Cs Be2B12, C2v Be3B12内部存在电子转移情况, Be原子2s轨道上失去电子, Be—B键主要以离子作用为主, 同时也存在共价作用. 成键分析显示Cs Be2B12C2v Be3B12的π键遵循球状芳香性2(n+1)2 (n=1)电子计数规则, 表明该团簇具有球状芳香性. 预测了三个结构的红外和拉曼光谱, 为以后的合成实验和数据表征提供了理论基础.  相似文献   

5.
采用密度泛函理论PBE0方法, 在aug-cc-pVTZ水平上理论预测了含平面五配位硅和锗原子的XBe5H6 (X=Si, Ge)团簇. 势能面系统搜索及高精度量化计算表明, 它们均为全局极小结构. XBe5H6(X=Si, Ge)团簇整体呈完美的扇形结构: Si/Ge原子被5个金属Be原子配位; 4个H原子以桥基方式与Be原子相键连, 剩余的2个 H原子以端基方式与两端的Be原子成键. 化学键分析表明, XBe5H6(X=Si, Ge) 团簇中XBe5单元具有完全离域的1个π及3个σ键, 外围铍氢间形成4个Be—H—Be 三中心二电子(3c-2e)键及2个定域的Be—H键. XBe5单元上离域的2π及6σ电子赋予体系πσ双重芳香性, 并使Si/Ge原子满足八隅律(或八电子规则). 能量分解-化学价自然轨道分析揭示, Si/Ge和Be5H6之间主要为电子共享键.  相似文献   

6.
新型环保绝缘气体七氟异丁腈(C4)在高压输电应用中备受关注. 本文采用多种高精度量子化学理论方法研究了C4吸附电子后形成C4-负离子的结构、 光谱、 寿命以及与CO2的反应机理和动力学. 结果表明, 电子进入C≡N的π*反键轨道, 通过弯曲C—C=N形成C4-负离子, 绝热电子亲合能的最佳预测值为0.30 eV. 在 0~2 eV范围内C4-具有显著的光电子吸收峰, 亚稳态C4-负离子经约9 kJ/mol能垒断裂C—F键生成稳定的长寿命[F...(CF3)2CCN]-中间体. C4-+CO2反应存在进攻F或CN上的C和N 3种复合-解离机理, 在电气应用条件下, 以CO2进攻氰基CN途径为主, 诱发负电荷从CN向CO2转移.  相似文献   

7.
PdYH分子的结构与势能函数   总被引:8,自引:1,他引:7  
倪羽  蒋刚  朱正和  孙颖 《化学学报》2005,63(8):764-768
用密度泛函理论的B3LYP方法, 对钯和钇原子采用SDD收缩价基函数, 氢原子采用6-311++G**全电子基函数, 对PdY和PdYH体系的结构进行优化. 计算表明: PdY分子的几何构型为Cv, 其基态为X2Σ态, 键长R=0.24168 nm, 离解能为De=2.8261 eV, 谐振频率ωe=254.0656 cm-1, 并拟合得到Murrell-Sorbie势能函数; PdYH分子最稳态为Cs构型, 电子组态为1A', 平衡核间距RPdY=0.24281 nm, RYH=0.19824 nm, 键角∠PdYH=116.7157°, 离解能De=5.6146 eV, 基态简正振动频率: 对称伸缩振动频率ν1 (a')=348.2909 cm-1, 弯曲振动频率ν2 (a')=243.3382 cm-1, 反对称伸缩振动频率ν3 (a')=1442.2695 cm-1. 由微观过程的可逆性原理分析了分子的可能离解极限. 并用多体项展式理论方法分别导出基态PdY和PdYH分子的势能函数, 其等值势能面图准确地再现了PdY和PdYH分子的结构特征和离解能, 由此讨论了Pd+Y+H分子反应的势能面静态特征.  相似文献   

8.
肖岸  卢辉  赵阳  骆耿耿 《物理化学学报》2016,32(12):2968-2975
选择N,N'-二甲基苯胺作为电子给体,乙炔基和苯基作为π桥键,苯并噻二唑基团作为辅助受体,氰基丙烯酸为电子受体设计合成了一个具有D-π-A-π-A结构的有机染料OD2。对该染料的光谱性能和电化学性能进行了研究,并将其用作光敏剂引入太阳能光电转化和光解水制氢领域。当OD2应用于光伏领域:在AM1.5(100 mW·cm-2)的光强下,OD2敏化的电池的光电转化效率(η)为4.40%(短路电流密度(Jsc)=10.58 mA·cm-2,开路电压(Voc)=630 mV,填充因子(FF)=0.65);当OD2应用于染料敏化可见光催化制氢领域:在300 W氙灯光源可见光照射10 h,OD2敏化的Pt/TiO2在pH=7.0,10%(φ,体积分数)三乙醇胺水溶液中的催化转化数(TON)为140,相应的表观制氢量子产率(ΦH2)仅为0.42%。显然,OD2在光电转化领域比可见光催化分解水制氢领域更具有应用潜力。  相似文献   

9.
采用水热法合成了5个稀土配合物[Sm2(bdbc)2(phen)4](1)和[Ln(bdbc)(phen)(H2O)][Ln=Eu(2), Gd(3), Tb(4), Dy(5), bdbc=(2-羧基苯氧基)苯-1,2-二羧酸根, phen=1,10-邻菲啰啉]. 配合物1是双核分子, 通过氢键和C—H…π作用进一步构筑成一维超分子结构; 配合物2~5是同构的一维双螺旋结构, 通过氢键和C—H…π作用进一步构筑成三维超分子结构. 配合物1, 2, 4和5呈现了Sm3+, Eu3+, Tb3+和Dy3+离子的特征发射, 分别对应于Sm3+离子的4G5/26HJ/2(J=5, 7, 9)、 Eu3+离子的5D07FJ(J=1—4)、 Tb3+离子的5D47FJ(J=6, 5, 4, 3)和Dy3+离子的4F5/26HJ/2(J=15, 13)跃迁. 对配合物4的荧光性质进行了表征, 结果表明, 配合物4可用作荧光探针以检测阳离子和苯甲醛.  相似文献   

10.
选择N-正丁基咔唑作为电子给体,芴酮作为桥键,苯甲酸作为受体,通过桥键芴酮与给体和受体连接位置的改变,设计合成了两个咔唑染料4-(6-(N-正丁基咔唑-3-基)-9-氧-9H-芴-3-基)苯甲酸(HXL-3W)和4-(7-(N-正丁基咔唑-3-基)-9-氧-9H-芴-2-基)苯甲酸(HXL-4Z).对咔唑染料的光谱性能、电化学性能和光电转换性能进行了研究,并运用密度泛函理论(DFT)方法对其几何结构和紫外-可见光谱进行了优化计算.结果表明, HXL-4Z的吸收光谱呈现两个明显的ππ*跃迁吸收峰和一个较小的对应于分子内电荷转移的吸收峰,而HXL-3W的吸收光谱则仅呈现一个ππ*跃迁吸收峰,且摩尔吸光系数远小于HXL-4Z.可能是HXL-3W分子结构中给体和受体距离较近,张力较大,导致较差的分子平面性和分子内电荷转移.因而HXL-4Z的光吸收能力和电子注入效率较优,从而具有较好的光电转换效率(2.03%) (短路电流(JSC) = 3.88 mA·cm-2,开路电压(VOC) = 700 mV,填充因子(FF) = 0.75).  相似文献   

11.
Geometries and binding energies are predicted at B3LYP/6-311+G* level for the adenine–BX3 (X=F,Cl) systems and four conformers with no imaginary frequencies have been obtained for both adenine–BF3 and adenine–BCl3, respectively, and single energy calculations using much larger basis sets (6-311+G(2df,p)) and aug-cc-pVDZ were carried out as well. The most stable conformer is BF3 or BCl3 connected to N3 of adenine and with the stabilization energy of 22.55 or 20.59 kcal/mol at B3LYP/6-311+G* level (BSSE corrected). The analyses for the combining interaction between BX3 and adenine with natural bond orbital method (NBO) and the atom-in-molecules theory (AIM) have been performed. The results indicate that all the conformers were formed with σ–p type interactions between adenine and BX3, in which pyridine-type nitrogen or nitrogen atom of amino group offers its lone pair electron to the empty p orbital of boron atom and the concomitances of charge transference from adenine to BX3 were occurred. Frequency analysis suggested that the stretching vibration of BX3 underwent a red shift in complexes. Adenine–BF3 complex was more stable than adenine–BCl3 although the distance of B–N is shorter in the later.  相似文献   

12.
毕一飘  宫雪  杨发  阮明波  宋平  徐维林 《应用化学》2020,37(9):1048-1055
氨在人类的生产生活中起着重要的作用,但目前工业上合成氨广泛采用的Haber-Bosch法耗能大,且污染严重。 而N2电还原反应(ENRR)被认为是一种有效的替代方法,由于N2的键能较高,目前仍然缺乏高活性的催化剂。 在这里,通过简单的浸渍法和氧化还原法制备了多价态的MnOx/C催化剂,该催化剂具有较高的氮还原反应活性(氨产率达到7.8 μgNH3/(h·mgcat),法拉第效率高达9.2%) 。进一步研究表明,多价态MnOx/C催化剂具有高氮还原反应活性的主要原因是不同价态的Mn离子(Mn2+、Mn3+、Mn4+)之间存在协同效应。  相似文献   

13.
采用 DMol 3 模块中广义梯度密度泛函理论(GGA)的Perdew-Burke-Ernzerh(PBE)方法研究含能材料分解气体产物NO, NO2在ZnO(10 1 ˉ 0)表面的吸附和NO2解离生成NO和O的过程. 结果表明, 优化后的吸附构型显示Zn顶位为稳定吸附位点, NO2的吸附能大于NO. 态密度图分析结合差分电荷密度图表明, NO的N原子与表面Zn有相互作用, 电荷从NO转移到表面; NO2的N2p, O2p轨道与表面Zn3d轨道发生杂化, NO2附近积累大量负电荷. 过渡态搜索显示NO2的解离需跨过较高能垒, 不易进行.  相似文献   

14.
The reaction: F + HCl→ HF (v 3) + Cl (1), has been initiated by photolysing F2 using the fourth-harmonic output at 266 nm from a repetitively pulsed Nd: YAG laser By analysing the time-dependence of the HF(3,0) vibrational chemiluminescence, rate constants have been determined at (296 ± 5) K for reaction (1), k1 = (7.0 ± 0.5) × 10−12 cm3 molecule−1 s−1, and for the relaxation of HF(v = 3) by HCl, CO2, N2O, CO, N2 and O2: kHCl = (1.18 ±0.14) × 10−11 kCO2 = (1.04 ± 0. 13) × 10−12, kN2O = (1.41 ± 0.13) × 10−11 kCO = (2.9 ± 0.3) × (10−12, kN2 = (7.1 ± 0.6) × 10−14 and kO2 = (1.9 ± 0.6) × 10−14 cm3molecule−1s−1.  相似文献   

15.
The chiral bis-imine (1R,2R)-C6H10-[E---N=CH---C6H3---3,4-(OMe)2]2 1 (LH) reacts with [Pd(OAc)2] (1:1 molar ratio; OAc=acetate) giving the orthometallated [Pd(OAc)(C6H2---4,5-(OMe)2---2-CH=N-(1R,2R)-C6H10---N=CH---C6H3-3′,4′-(OMe)2-κ-C,N,N)] 2 (abbreviated as [Pd(OAc)(L-κ-C,N,N)]), through C---H bond activation on only one of the aryl rings and N,N-coordination of the two iminic N atoms. 2 reacts with an excess of LiCl to give [Pd(Cl)(L-κ-C,N,N)] 3. The reaction of 3 with AgClO4 and neutral or anionic ligands L′ (1:1:1 molar ratio) affords [Pd(L-κ-C,N,N)(L′)](ClO4) (L′=PPh3 4a, NCMe 5, pyridine 6, p-nitroaniline 7) or [Pd(I)(L-κ-C,N,N)] 8. Complex 4a reacts with wet CDCl3 giving [Pd(C6H2---4,5-(OMe)2---2-CH=N-(1R,2R)---C6H10---NH2-κ-C,N,N)(PPh3)](ClO4) 4b as a result of the hydrolysis of the C=N bond not involved in the orthometallated ring. The molecular structure of 4b·CH2Cl2 has been determined by X-ray diffraction methods. Cleavage of the Pd---N bond trans to the Caryl atom can be accomplished by coordination of strongly chelating ligands, such as acetylacetonate (acac) or bis(diphenylphosphino)ethane (dppe), forming [Pd(acac-O,O′)(L-κ-C,N)] 9 and [Pd(L-κ-C,N)(dppe-P,P′)](ClO4) 12, while classical N,N′-chelating ligands such as 1,10-phenantroline (phen) or 2,2′-bipyridyl (bipy) behave as monodentate N-donor ligands yielding [Pd(L-κ-C,N,N)(κ1-N-phen)](ClO4) 10 and [Pd(L-κ-C,N,N)(κ1-N-bipy)](ClO4) 11. Treatment of 1 with PtCl2(DMSO)2 (1:1 molar ratio) in refluxing 2-methoxyethanol gives Cl2Pt[(NH2)2C6H10---N,N′] 13a and [Pt(Cl)(C6H2---4,5-(OMe)2---2-CH=N-(1R,2R)---C6H10---NH2-κ-C,N,N)] 13b, while [Pt(Cl)(L-κ-C,N,N)] 14 can be obtained by reaction of [Pt(μ-Cl)(η3-2-Me---C3H4)]2 with 1 in refluxing CHCl3. Complexes 2 and 3 catalyzed the arylation of methyl acrylate giving good yields of the corresponding methyl cinnamates and TON up to 847 000. Complex 3 also catalyzes the hydroarylation of 2-norbornene, but with lower yields and without enantioselectivity.  相似文献   

16.
Molecular structures of (triphenylphosphine) [1,1′-bis-(methylthio)ferrocene-S,S′,Fe]Pt(BF4)2 (1), (1,5,9-trithia[9]ferrocenophane-S,S′,S″,Fe)Pd(BF4)2 (2), and (acetonitrile)(1,4,7-trithia[7]ferrocenophane-S,S′,S″,Fe)Pd(BF4)2 (3) were determined by X-ray analyses. The Pt in 1 and the Pd atom in 2 have a somewhat distorted square-planar geometry including the Fe atom of the ferrocene moiety, while the Pd atom in 3 is coordinated by one equivalent of acetonitrile and takes a distorted tetragonal-pyramidal geometry. The distances of the Fe---M bond (M = Pd, Pt) in 1–3 are 2.851(2), 2.827(2), and 3.0962(8) Å, respectively. Cyclic voltammetry of 1–3 gave no reversible wave, but afforded some information supporting the presence of a dative bond.  相似文献   

17.
A nonlocal density functional theory (DFT) method has been applied to the calculations on optimized geometry, Mulliken atomic net charges and interatomic Mulliken bond orders as well as total bonding energies (E) in the binary transition metal carbonyl anions with different reduced states [M(CO)n]z (M=Cr, n=5, 4, 3, z=2, 4, 6; M=Mn, n=5, 4, 3, z=1, 3, 5; M=Fe, n=4, 3, 2, z=2, 4, 6; M=Co, n=4, 3, 2, z=1, 3, 5). For comparison of relative stability, a relative stabilization energy D is defined as D=E([M(CO)n]z)-nE(CO). The calculated C-O distances are lengthened monotonously with the increase of the anionic charge, but the M-C distances are significantly lengthened only in the higher reduced states. The relative stabilization energy calculated is a considerable negative value in the lower reduced states, but a larger positive value in the higher reduced states. The DFT calculations show that with the increase of the anionic charge, the Mulliken net charges on the M, C, and O atoms all increase, however, an excess of the anionic charge is mainly located at the central metal atom. The calculated C-O Mulliken bond orders decrease consistently with the increase of the anionic charge, but the M-C bond orders exhibit an irregular behavior. However, the total bond orders calculated clearly explain the higher reduced states to be considerably unstable. From analysis of the calculated results, it is deduced that the stability of the binary transition metal carbonyl anions [M(CO)n]z studied are associated with the coordination number n and the anionic charge z, further, it is possible for the anions studied to be stable if nz, conversely, it is impossible when n<z.  相似文献   

18.
Geometries and vibrational frequencies of complexes of cationic coinage metal clusters Mn+ (M=Cu, Ag, Au; n=1–4) and H2S are computed using density functional theory. Thermochemical values for Mn+H2S decomposition channels involving loss of an H atom, H2 molecule, M atom, or M2 molecule are also computed. Significantly different results are obtained for closed-shell (n odd) and open-shell (n even) complexes.  相似文献   

19.
The reaction between zinc(II) azide, Zn(N3)2 and aminopyrazine (ampyz) afforded the complexes: [Zn(N3)2(ampyz)2] (1), [Zn(N3)2(ampyz)]n (2) and [Zn3(N3)6(ampyz)2]n (3). These complexes are characterized by spectroscopic and crystallographic methods. The IR spectra of these compounds are measured and discussed. The structure of 1 consists of isolated tetrahedral zinc atom surrounded by two mono-dentate N-ampyz and two terminal azido ligands. Complex 2 features a zigzag chain of zinc centers in which each zinc is surrounded by alternate di-EO (end-on) and di-EE (end-to-end) azide bridges, the chain thus contains alternate four-membered Zn2N2 and eight-membered Zn2(NNN)2 rings. The two ampyz ligands are located in cis-arrangement and each of them further binds another zinc atom giving rise to a 3D network. Complex 3 contains two structurally different zinc atoms; the six-coordinate Zn(1) center links two di-EO azido bridges and two trans ampyz, thus having ZnN6 chromophore. The five-coordinate Zn(2) center binds two di-EO bridging azido groups and the fifth position is occupied by an N atom from a bridging ampyz molecule. Both zinc centers, therefore participate in the formation of a 1D chain of cyclic Zn2N2 units. Each ampyz ligand binds another zinc atom via the second pyrazinic N atom giving another cross-chain and thus the structure consists of 2D sheets. In these three complexes the azido ligands of all types are asymmetric and linear within the experimental error.  相似文献   

20.
运用密度泛函理论系统研究了甲烷在MV_3O_y~q (M=Au/Ag,y=6–8,q=0或±1)团簇上的吸附和活化。研究得到了吸附体系的微观几何构型、吸附能、电荷分布等性质,找到了5个可以明显活化甲烷分子的含Au团簇。在这些体系中,Au均吸附在基底团簇V_3O_y~q的O位置,而CH_4均在Au原子上被活化。团簇电荷对活化能力有明显影响,阳离子团簇的活化能力最强,中性体系次之,阴离子团簇的活化能力很弱。测试计算表明引入D3色散矫正对于体系结构和能量的计算结果影响不大。本文作为单原子催化剂上甲烷吸附和活化反应的团簇模型研究,为进一步研究单原子催化剂上甲烷的活化机理提供了基础,也为合理设计低温下甲烷转化的单原子催化剂提供了有益的线索。  相似文献   

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