Type‐I Dyotropic Reactions: Understanding Trends in Barriers

To understand the factors that control the activation barrier of type‐I 1,2‐dyotropic reactions (X‐EH₂‐CH₂‐X*→X*‐EH₂‐CH₂‐X, with E=C and Si, X=H, CH₃, SiH₃, F to I) and trends therein as a function of the migrating groups X, we have explored ten archetypal model reactions of this class using relativistic density functional theory (DFT) at ZORA‐OLYP/TZ2P. The main trends in reactivity are rationalized using the activation strain model of chemical reactivity, which had to be extended from bimolecular to unimolecular reactions. Thus, the above type‐I dyotropic reactions can be conceived as a relative rotation of the CH₂CH₂ and [X???X] fragments in X‐CH₂‐CH₂‐X. The picture that emerges from these analyses is that reduced C? X bonding in the transition state is the origin of the reaction barrier. Also the trends in reactivity on variation of X can be understood in terms of how sensitive the C? X interaction is towards adopting the transition‐state geometry. A valence bond analysis complements the analyses and confirms the picture emerging from the activation strain model.     

Analysis of tertiary phosphanes, arsanes, and stibanes as bridging ligands in dinuclear Group 9 complexes

The unusual bridging and semi‐bridging binding mode of tertiary phosphanes, arsanes, and stibanes in dinuclear low‐valent Group 9 complexes have been studied by density functional methods and bonding analyses. The influence of various parameters (bridging and terminal ligands, metal atoms) on the structural preferences and bonding of dinuclear complexes of the general composition [A¹ M¹(μ‐CH₂)₂(μ‐EX₃)M² A²] (M¹, M²=Co, Rh, Ir; A¹, A²=F, Cl, Br, I, κ²‐acac; E=P, As, Sb, X=H, F, CH₃) has been analyzed. A number of factors have been identified that favor bridging or semi‐bridging modes for the phosphane ligands and their homologues. A more symmetrical position of the bridging ligand EX₃ is promoted by more polar E? X bonding, but by less electronegative (softer) terminal anionic ligands. Among the Group 9 metal elements Co, Rh, and Ir, the computations clearly show that the 4d element rhodium exhibits the largest preference for a {M¹(μ‐EX₃)M²} bridge, in agreement with experimental observation. Iridium complexes should be valid targets, whereas cobalt does not seem to support well a symmetric bridging mode. Analyses of the Electron Localization Function (ELF) indicate a competition between a delocalized three‐center bridge bond and direct metal–metal bonding.     

Phenylene‐Bridged Core‐Modified Planar Aromatic Octaphyrin: Aromaticity,Photophysical and Anion Receptor Properties

The synthesis of a planar expanded meso porphyrin with an intramolecular para‐phenylene‐bridged core is reported. The planarity of the octaphyrin macrocycle was confirmed by single‐crystal X‐ray structural analysis, in which the bridged para‐phenylene unit deviated by 27° from the mean macrocyclic plane. Spectroscopic analyses and theoretical calculations suggested that the macrocycle was Hückel aromatic and followed a major [34 π] single‐conjugation pathway, which indicated that the bridging para‐phenylene unit was not involved in the macrocyclic conjugation. Analysis of the photophysical properties of this system by steady‐state absorption/fluorescence spectroscopy and transient absorption spectroscopy revealed moderate enhancement in the parameters of the octaphyrin as compared to its non‐bridged octaphyrin congeners, which was attributed to the planarity and rigidity of the macrocycle as imposed by the bridging para‐phenylene unit. Preliminary anion‐binding studies revealed that the protonated macrocycle bound selectively with chloride ions through N?H???Cl hydrogen‐bonding interactions.     

Poly­[[[aqua­manganese(II)]‐μ2‐4,4′‐bi­pyridine‐μ3‐succinato] 4,4′‐bi­pyridine hemisolvate]

The polymeric title complex, {[Mn(C₄H₄O₄)(C₁₀H₈N₂)(H₂O)]·0.5C₁₀H₈N₂}_n, possesses a three‐dimensional open‐framework structure, with the solvate 4,4′‐bi­pyridine (bipy) mol­ecules, which lie around centers of inversion, clathrated in the channels of the framework. The Mn^II center is surrounded by three succinate (succ) ligands, one water mol­ecule and two bipy ligands, and displays a slightly distorted octahedral coordination environment, with cis angles ranging from 84.14 (12) to 96.56 (11)°. Each succ dianion coordinates to three Mn^II atoms, thus acting as a bridging tridentate ligand; in turn, the Mn^II atoms are bridged by three succ ligands, thus forming a two‐dimensional Mn–succ sheet pillared by the bridging bipy ligands. Two hydrogen‐bonding interactions, involving the water mol­ecules and the carboxy O atoms of the succ ligands, are present in the crystal structure.     

Resonance Character of Copper/Silver/Gold Bonding in Small Molecule⋅⋅⋅MX (X=F,Cl, Br,CH3, CF3) Complexes

The resonance character of Cu/Ag/Au bonding is investigated in B???M?X (M=Cu, Ag, Au; X=F, Cl, Br, CH₃, CF₃; B=CO, H₂O, H₂S, C₂H₂, C₂H₄) complexes. The natural bond orbital/natural resonance theory results strongly support the general resonance‐type three‐center/four‐electron (3c/4e) picture of Cu/Ag/Au bonding, B:M?X?B⁺?M:X^?, which mainly arises from hyperconjugation interactions. On the basis of such resonance‐type bonding mechanisms, the ligand effects in the more strongly bound OC???M?X series are analyzed, and distinct competition between CO and the axial ligand X is observed. This competitive bonding picture directly explains why CO in OC???Au?CF₃ can be readily replaced by a number of other ligands. Additionally, conservation of the bond order indicates that the idealized relationship b_B???M+b_MX=1 should be suitably generalized for intermolecular bonding, especially if there is additional partial multiple bonding at one end of the 3c/4e hyperbonded triad.     

新的杯[4]芳烃衍生物通过缔合乙腈进行自插入的X-射线衍射和密度泛函理论研究

合成和表征了一个新的杯[4]芳烃衍生物，11,23-二羟亚胺甲基-25,27-二羟基-26,28-二丙氧基杯[4]芳烃 (B)及其与乙腈生成的组成为B·2CH₃CN的化合物。¹H NMR显示，在B·2CH₃CN中B采取锥型构象，X-射线衍射分析确证在溶液中所发现的构象。在晶格网络中存在着B·2CH₃CN以二聚体形式的自插入现象。在B3LYP/6-311G(d)水平上计算了该自插入二聚体中的非共价相互作用能，并对基集叠加误差进行了校正。在二聚体中的B·2CH₃CN，一个CH₃CN通过与羟亚胺基形成氢键使之稳定，结合能为–5.02 kJ·mol^-1，另一个CH₃CN则通过与另一个羟亚胺基形成氢键以及与另一B·2CH₃CN中B苯环空腔间的C–H···π相互作用使之稳定，结合能分别为–14.23 kJ·mol^-1和–3.77 kJ·mol^-1。自插入的驱动能为–7.54 kJ·mol^-1。     

DNA/BSA‐binding property and in vitro anticancer activity of a new dicopper(II) complex with N‐(2‐hydroxy‐5‐nitrophenyl)‐N′‐[3‐(diethylamino)propyl]oxamide as bridging ligand: Synthesis and crystal structure

A new oxamido‐bridged dicopper(II) complex formulated as [Cu₂(ndpox)(bpy)(CH₃OH)₂]‐ (ClO₄), where H₃ndpox is N‐(2‐hydroxy‐5‐nitrophenyl)‐N′‐[3‐(diethylamino)propyl]oxamide; and bpy represents 2,2′‐bipyridine, was synthesized and structurally characterized using X‐ray single‐crystal diffraction and other methods. In the molecule, the endo‐ and the exo‐copper(II) ions bridged by the cis ‐ndpox³⁻ ligand are in {N₃O₂} and {N₂O₃} square‐ pyramidal environments, respectively. There is a three‐dimensional hydrogen bonding network dominated by O‐H···O and C‐H···O interactions in the crystal. The reactivity toward DNA/protein bovine serum albumin (BSA) revealed that the complex could interact with herring sperm DNA (HS‐DNA) through the intercalation mode, and effectively quench the intrinsic fluorescence of BSA via a static process. Cytotoxicity studies suggest that the complex displays selective cancer cell antiproliferative activity. The present investigation confirmed that the combined effects of both electron‐withdrawing and hydrophobic groups on the bridging ligand in the dicopper(II) complex systems can increase DNA/BSA‐binding ability and in vitro anticancer activity.     

Synthesis and Characterization of [XeOXe]2+ in the Adduct‐Cation Salt, [CH3CN‐ ‐ ‐XeOXe‐ ‐ ‐NCCH3][AsF6]2

Acetonitrile and [FXeOXe‐ ‐ ‐FXeF][AsF₆] react at ?60 °C in anhydrous HF (aHF) to form the CH₃CN adduct of the previously unknown [XeOXe]²⁺ cation. The low‐temperature X‐ray structure of [CH₃CN‐ ‐ ‐XeOXe‐ ‐ ‐NCCH₃][AsF₆]₂ exhibits a well‐isolated adduct‐cation that has among the shortest Xe?N distances obtained for an sp‐hybridized nitrogen base adducted to xenon. The Raman spectrum was fully assigned by comparison with the calculated vibrational frequencies and with the aid of ¹⁸O‐enrichment studies. Natural bond orbital (NBO), atoms in molecules (AIM), electron localization function (ELF), and molecular electrostatic potential surface (MEPS) analyses show that the Xe?O bonds are semi‐ionic whereas the Xe?N bonds may be described as strong electrostatic (σ‐hole) interactions.     

catena‐Poly[[tetra­aqua­manganese(II)]‐μ‐4‐(carboxyl­ato­methyl­sulfanyl)­phenoxy­acetato]

The title compound, [Mn(C₁₀H₈O₅S)(H₂O)₄]_n, a one‐dimensional manganese(II) complex comprising helical chains bridged by 4‐(carboxylatomethylsulfanyl)phenoxyacetate ligands has been characterized by single‐crystal X‐ray diffraction analysis. Hydrogen‐bonding inter­actions between adjacent chains extend the complex into a three‐dimensional supra­molecular architecture.     

Metal‐Templated,Tight Loop Conformation of a Cys‐X‐Cys Biomimetic Assembles a Dimanganese Complex

With the goal of generating anionic analogues to MN₂S₂ ? Mn(CO)₃Br we introduced metallodithiolate ligands, MN₂S₂^2? prepared from the Cys‐X‐Cys biomimetic, ema^4? ligand (ema=N,N′‐ethylenebis(mercaptoacetamide); M=Ni^II, [V^IV≡O]²⁺ and Fe^III) to Mn(CO)₅Br. An unexpected, remarkably stable dimanganese product, (H₂N₂(CH₂C=O(μ‐S))₂)[Mn(CO)₃]₂ resulted from loss of M originally residing in the N₂S₂^4? pocket, replaced by protonation at the amido nitrogens, generating H₂ema^2?. Accordingly, the ema ligand has switched its coordination mode from an N₂S₂^4? cavity holding a single metal, to a binucleating H₂ema^2? with bridging sulfurs and carboxamide oxygens within Mn‐μ‐S‐CH₂‐C‐O, 5‐membered rings. In situ metal‐templating by zinc ions gives quantitative yields of the Mn₂ product. By computational studies we compared the conformations of “linear” ema^4? to ema^4? frozen in the “tight‐loop” around single metals, and to the “looser” fold possible for H₂ema^2? that is the optimal arrangement for binucleation. XRD molecular structures show extensive H‐bonding at the amido‐nitrogen protons in the solid state.     

First‐Row Transition‐Metal–Diborane and –Borylene Complexes

A combined experimental and quantum chemical study of Group 7 borane, trimetallic triply bridged borylene and boride complexes has been undertaken. Treatment of [{Cp*CoCl}₂] (Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) with LiBH₄ ? thf at ?78 °C, followed by room‐temperature reaction with three equivalents of [Mn₂(CO)₁₀] yielded a manganese hexahydridodiborate compound [{(OC)₄Mn}(η⁶‐B₂H₆){Mn(CO)₃}₂(μ‐H)] ( 1 ) and a triply bridged borylene complex [(μ₃‐BH)(Cp*Co)₂(μ‐CO)(μ‐H)₂MnH(CO)₃] ( 2 ). In a similar fashion, [Re₂(CO)₁₀] generated [(μ₃‐BH)(Cp*Co)₂(μ‐CO)(μ‐H)₂ReH(CO)₃] ( 3 ) and [(μ₃‐BH)(Cp*Co)₂(μ‐CO)₂(μ‐H)Co(CO)₃] ( 4 ) in modest yields. In contrast, [Ru₃(CO)₁₂] under similar reaction conditions yielded a heterometallic semi‐interstitial boride cluster [(Cp*Co)(μ‐H)₃Ru₃(CO)₉B] ( 5 ). The solid‐state X‐ray structure of compound 1 shows a significantly shorter boron–boron bond length. The detailed spectroscopic data of 1 and the unusual structural and bonding features have been described. All the complexes have been characterized by using ¹H, ¹¹B, ¹³C NMR spectroscopy, mass spectrometry, and X‐ray diffraction analysis. The DFT computations were used to shed light on the bonding and electronic structures of these new compounds. The study reveals a dominant B?H?Mn, a weak B?B?Mn interaction, and an enhanced B?B bonding in 1 .     

Poly[diaqua­(μ‐4,4′‐bipyridine)tetra­kis­(μ‐ferro­cenecarboxyl­ato)bis­(ferro­cenecarboxyl­ato)­tri­man­ganese(II)]

The title compound, [Mn₃Fe₆(C₅H₅)₆(C₆H₄O₂)₆(C₁₀H₈N₂)(H₂O)₂]_n, consists of two crystallographically unique Mn^II centers. One is situated on an inversion center and is octa­hedrally coordinated by two N atoms from two bridging 4,4′‐bipyridine (4,4′‐bipy) ligands and four O atoms, two from different bridging ferrocenecarboxyl­ate (μ₂‐FcCOO⁻; Fc is ferrocene) units and two from aqua ligands. The two halves of each 4,4′‐bipy ligand are related by a center of symmetry. The second Mn^II center is in a strongly distorted tetra­gonal–pyramidal geometry, coordinated by five O atoms, three from three μ₂‐FcCOO⁻ units and two from a fourth, chelating, η²‐FcCOO⁻ unit. The FcCOO⁻ units function as bridging ligands to adjacent Mn^II centers, leading to the formation of linear ⋯Mn1Mn2Mn2Mn1⋯ chains. Adjacent chains are further bridged by 4,4′‐bipy ligands, resulting in a two‐dimensional layered polymer.     

A cyanide‐bridged FeIII–MnII heterobimetallic one‐dimensional coordination polymer: synthesis,crystal structure,experimental and theoretical magnetism investigation

A new cyanide‐bridged Fe^III–Mn^II heterobimetallic coordination polymer (CP), namely catena‐poly[[[N,N′‐(1,2‐phenylene)bis(pyridine‐2‐carboxamidato)‐κ⁴N,N′,N′′,N′′′]iron(III)]‐μ‐cyanido‐κ²C:N‐[bis(4,4′‐bipyridine‐κN)bis(methanol‐κO)manganese(II)]‐μ‐cyanido‐κ²N:C], {[FeMn(C₁₈H₁₂N₄O₂)(CN)₂(C₁₀H₈N₂)₂(CH₃OH)₂]ClO₄}_n, ( 1 ), was prepared by the self‐assembly of the trans‐dicyanidoiron(III)‐containing building block [Fe(bpb)(CN)₂]^? [bpb^2? = N,N′‐(1,2‐phenylene)bis(pyridine‐2‐carboxamidate)], [Mn(ClO₄)₂]·6H₂O and 4,4′‐bipyridine, and was structurally characterized by elemental analysis, IR spectroscopy, single‐crystal X‐ray crystallography and powder X‐ray diffraction (PXRD). Single‐crystal X‐ray diffraction analysis shows that CP 1 possesses a cationic linear chain structure consisting of alternating cyanide‐bridged Fe–Mn units, with free perchlorate as the charge‐balancing anion, which can be further extended into a two‐dimensional supramolecular sheet structure via inter‐chain π–π interactions between the 4,4′‐bipyridine ligands. Within the chain, each Mn^II ion is six‐coordinated by an N₆ unit and is involved in a slightly distorted octahedral coordination geometry. Investigation of the magnetic properties of 1 reveals an antiferromagnetic coupling between the cyanide‐bridged Fe^III and Mn^II ions. A best fit of the magnetic susceptibility based on the one‐dimensional alternating chain model leads to the magnetic coupling constants J₁ = ?1.35 and J₂ = ?1.05 cm^?1, and the antiferromagnetic coupling was further confirmed by spin Hamiltonian‐based density functional theoretical (DFT) calculations.     

Shifting Paradigms: Electrostatic Interactions and Covalent Bonding

The role of electrostatic interactions in covalent bonding of heavier main group elements has been evaluated for the exemplary set of molecules X₂H₂ (X=C, Si, Ge, Sn, Pb). Density functional calculations at PBE/QZ4P combined with energy decomposition procedures and kinetic energy density analyses have been carried out for a variety of different structures, and two factors are responsible for the fact that the heavier homologues of acetylene exhibit doubly hydrogen‐bridged local minimum geometries. For one, the extended electronic core with at least one set of p orbitals of the Group 14 elements beyond the first long period is responsible for favorable electrostatic E–H interactions. This electrostatic interaction is the strongest for the isomer with two bridging hydrogen atoms. Secondly, the H substituent does not posses an electronic core or any bonding‐inactive electrons, which would give rise to a significant amount of Pauli repulsion, disfavoring the doubly bridged isomer. When one of two criteria is not met the unusual doubly bridged structure no longer constitutes the energetically preferred geometry. The bonding model is validated in calculations of different structures of Si₂(CH₃)₂.     

Experimental Determination of Magnetic Anisotropy in Exchange‐Bias Dysprosium Metallocene Single‐Molecule Magnets

We investigate a family of dinuclear dysprosium metallocene single‐molecule magnets (SMMs) bridged by methyl and halogen groups [Cp′₂Dy(μ‐X)]₂ (Cp′=cyclopentadienyltrimethylsilane anion; 1 : X=CH₃^?; 2 : X=Cl^?; 3 : X=Br^?; 4 : X=I^?). For the first time, the magnetic easy axes of dysprosium metallocene SMMs are experimentally determined, confirming that the orientation of them are perpendicular to the equatorial plane which is made up of dysprosium and bridging atoms. The orientation of the magnetic easy axis for 1 deviates from the normal direction (by 10.3°) due to the stronger equatorial interactions between Dy^III and methyl groups. Moreover, its magnetic axes show a temperature‐dependent shifting, which is caused by the competition between exchange interactions and Zeeman interactions. Studies of fluorescence and specific heat as well as ab initio calculations reveal the significant influences of the bridging ligands on their low‐lying exchange‐based energy levels and, consequently, low‐temperature magnetic properties.     

1,2,4‐Triazole Controlled CdII/MnII Complexes with Discrete Mononuclear,Polymeric 1D Chain,and 2D Layer Motifs

Three Htrz‐based metal complexes, [Cd(trz)(CH₃OH)(nb)]_n ( 1 ), [Cd(Htrz)(H₂O)(nb)₂]_n ( 2 ), and {[Mn(Htrz)₂(H₂O)₄] · 2nb} ( 3 ) (Htrz = 1,2,4‐triazole, Hnb = 4‐nitrobenzoic acid), have been synthesized by diffusion or solvent evaporation method and structurally characterized by single crystal X‐ray crystallography, elemental analysis, IR and fluorescence spectroscopy, and TG‐DTA. Structural determinations revealed that complex 1 has a two‐dimensional (2D) layer structure constructed by tridentate μ_N1,N2,N4‐bridging trz anions and Cd^II ions. Complex 2 presents a 1D polymeric chain structure bridged by bidentate μ_N1,N4‐bridging Htrz molecule and Cd^II ions, whereas compound 3 is a supramolecular assembly containing a mononuclear [Mn(Htrz)₂(H₂O)₄]²⁺ dication and two free nb anions for charge compensation. Thus, the structural diversity of the three complexes is significantly governed by the coordination modes of the neutral/deprontated Htrz ligand, rather than the terminal/lattice nb anion. Additionally, the thermal stability of the complexes is observed to be dependent on the polymeric or discrete structure nature. At room temperature, the three solid complexes show Htrz‐based intraligand fluorescent emission.     

Study on the Reaction of Electron‐deficient Cyclopropane Derivatives with Amines

Reaction of electron deficient cyclopropane derivatives cis‐1‐methoxycarbonyl‐2‐aryl‐6, 6‐dimethyl‐5, 7‐dioxa‐spiro‐[2,5]‐4,8‐octadiones (1a‐d) (X = CH₃, H, Cl, NO₂) with anilines (2a‐e) (Y = p‐CH₃, H, p‐Br, p‐NO₂, o‐CH₃) at room temperature gives N‐aryl‐trans, trans‐α‐carboxyl‐β‐methoxycarbonyl‐γ‐aryl‐γ‐butyrolactams (3a‐p) in high yields with high stereoselectivity. For example, 1a (X= CH₃) reacts with ammonia 4 or benzyl amine 5 at room temperature to give inner ammonium salt 6 or 7 in the yield of 83% or 97% respectively. The reaction mechanisms for formation of the products are proposed.     

An Electron Dynamics Mechanism of Charge Separation in the Initial‐Stage Dynamics of Photoinduced Water Splitting in XMnWater (X=OH,OCaH) and Electron–Proton Acceptors

An electron dynamics mechanism of charge separation in the initial stage of excited‐state reactions of the class of X?Mn?OH₂???A${ \to }$ X?Mn?OH???HA (X=OH or OCaH; A=N‐methylformamidine, guanidine, imidazole, or ammonia cluster) is reported. The dynamic effect of calcium doping is also revealed. This study provides a novel factor to be considered in designing efficient systems for photoinduced water splitting.     

Silicon‐ and Tin‐Containing Open‐Chain and Eight‐Membered‐Ring Compounds as Bicentric Lewis Acids toward Anions

Herein, we report the syntheses of silicon‐ and tin‐containing open‐chain and eight‐membered‐ring compounds Me₂Si(CH₂SnMe₂X)₂ ( 2 , X=Me; 3 , X=Cl; 4 , X=F), CH₂(SnMe₂CH₂I)₂ ( 7 ), CH₂(SnMe₂CH₂Cl)₂ ( 8 ), cyclo‐Me₂Sn(CH₂SnMe₂CH₂)₂SiMe₂ ( 6 ), cyclo‐(Me₂SnCH₂)₄ ( 9 ), cyclo‐Me_(2?n)X_nSn(CH₂SiMe₂CH₂)₂SnX_nMe_(2?n) ( 5 , n=0; 10 , n = 1, X= Cl; 11 , n=1, X= F; 12 , n=2, X= Cl), and the chloride and fluoride complexes NEt₄[cyclo‐ Me(Cl)Sn(CH₂SiMe₂CH₂)₂Sn(Cl)Me?F] ( 13 ), PPh₄[cyclo‐Me(Cl)Sn(CH₂SiMe₂CH₂)₂Sn(Cl)Me?Cl] ( 14 ), NEt₄[cyclo‐Me(F)Sn(CH₂SiMe₂CH₂)₂Sn(F)Me?F] ( 15 ), [NEt₄]₂[cyclo‐Cl₂Sn(CH₂SiMe₂CH₂)₂SnCl₂?2 Cl] ( 16 ), M[Me₂Si(CH₂Sn(Cl)Me₂)₂?Cl] ( 17 a , M=PPh₄; 17 b , M=NEt₄), NEt₄[Me₂Si(CH₂Sn(Cl)Me₂)₂?F] ( 18 ), NEt₄[Me₂Si(CH₂Sn(F)Me₂)₂?F] ( 19 ), and PPh₄[Me₂Si(CH₂Sn(Cl)Me₂)₂?Br] ( 20 ). The compounds were characterised by electrospray mass‐spectrometric, IR and ¹H, ¹³C, ¹⁹F, ²⁹Si, and ¹¹⁹Sn NMR spectroscopic analysis, and, except for 15 and 18 , single‐crystal X‐ray diffraction studies.