Photochemical [2 + 2] cycloaddition as a tool to study a solid-state structural transformation

The solid-state structural transformation of the hydrogen-bonded 1D coordination polymer [Cd(bpe)(CH(3)COO)(2)(H(2)O)](n), to a ladder-type structure is evident from a photochemical [2 + 2] cycloaddition reaction forming 100% rctt-cyclobutane isomer.     

Solid-state photochemical [2+2] cycloaddition in a hydrogen-bonded metal complex containing several parallel and crisscross C=C bonds

One-dimensional hydrogen-bonded complex [Zn(bpe)(2)(H(2)O)(4)](NO(3))(2).8/3 H(2)O.2/3 bpe (1, bpe=4,4'-bipyridylethylene) containing coordination complex cations [Zn(bpe)(2)(H(2)O)(4)](2+) with parallel and crisscross double bonds undergoes photochemical [2+2] cycloaddition in the solid state and produces tetrakis(4-pyridyl)cyclobutane (tpcb) in up to 100 % yield with rctt-tpcb (2a) as major and rtct-tpcb (2b) as minor product. The bpe ligands with crisscross conformation of C=C bonds appear to undergo pedal-like motion prior to photodimerization. Grinding single crystals to powder accelerates the pedal motion of crisscrossed olefins in the bpe ligands to parallel alignment and provides the rctt-cyclobutane stereoisomer 2a quantitatively. In addition, 100 % photodimerization of ground 1 indicates that the free bpe ligands, which are remote from each other in a pool of water, and NO(3)(-) ions moved toward each other to give a mixture of rctt- and rtct-tpcb isomers.     

Structural diversity in manganese squarate frameworks using N,N-donor chelating/bridging ligands: syntheses, crystal structures and magnetic properties

Three new polymeric squarato-bridged manganese complexes {[Mn(H(2)O)(2)(bpe)(sq)].bpe.H(2)O}(n) (1), [Mn(2)(H(2)O)(4)(phen)(2)(sq)(2)](n) (2) and [Mn(2)(H(2)O)(2)(phen)(4)(sq)].(sq).8(H(2)O) (3) [bpe, 1,2-bis(4-pyridyl)ethane; phen, 1,10-phenanthroline; sq, squarate dianion] have been synthesized and characterized by single crystal X-ray diffraction analysis and variable temperature magnetic studies. Complex 1 is a 2D rectangular grid-like structure, achieved through flexible bpe bridging ligands and squarate dianions. On the other hand the use of chelating phen instead of bpe gives rise to a 1D polymeric chain in complex 2 and to a dinuclear entity in 3. In all the three complexes weak interactions play a vital role in stabilizing the solid-state structure. Variable temperature (2-300 K) magnetic studies indicate weak antiferromagnetic coupling between the metal centres in all the complexes.     

Mononuclear and dinuclear complexes with a [Ru(tBu2PCH2CH2PtBu2)(CO)] core

Thermolysis of solid [Ru(d(t)bpe)(CO)2Cl2](2, d(t)bpe =(t)Bu2PCH2CH2P(t)Bu2) under vacuum affords the five-coordinate complex [Ru(d(t)bpe)(CO)Cl2] (4), which was shown by X-ray crystallography to contain a weak remote agostic interaction. In solution, 4 can be readily trapped by CO, CH3CN or water to give [Ru(d(t)bpe)(CO)(L)Cl2](L = CO, 2; L = CH3CN, 6; L = H2O, 7). Reaction of 4 with AgOTf/H2O yields the tris-aqua complex [Ru(d(t)bpe)(CO)(H2O)3](OTf)2 (8), which has been structurally characterised and probed in solution by pulsed-gradient spin echo (PGSE) NMR spectroscopy. The water ligands in 8 are labile and easily substituted to give [Ru(d(t)bpe)(CO)(NCCH3)3](OTf)2 (10) and [Ru(d(t)bpe)(CO)(DMSO)3](OTf)2 (11). In the presence of CO, the tris-aqua complex undergoes water-gas shift chemistry with formation of the cationic hydride species [Ru(d(t)bpe)(CO)3H](OTf) (12) and CO2. X-Ray crystal structures of complexes 2, 4, 6, 8 and 11-12 are reported along with those for [{Ru(d(t)bpe)(CO)}2(mu-Cl)2(mu-OTf)](OTf) (3), [{Ru(d(t)bpe)(CO)}2(mu-Cl)3][Ru(d(t)bpe)(CO)Cl3](5) and [Ru(d(t)bpe)(CO)(H2O)2(OTf)](OTf)(9).     

Five novel transition metal coordination polymers with 2D/3D framework structure based on flexible H2tzda and ancillary ligand bpe

Five new transition metal coordination polymers based on H₂tzda and co-ligand bpe, {[M(tzda)(bpe)]·H₂O}_n [M=Zn(1), Cd(2), Mn(3), Co(4)] and [Ni₂(tzda)₂(bpe)₂(H₂O)]_n (5) [H₂tzda=(1,3,4-thiadiazole-2,5-diyldithio)diacetic acid, bpe=1,2-bis(4-pyridyl)ethane], have been hydrothermally synthesized and structurally characterized. Compounds 1-4 feature a 2D-layered architecture generated from [M(tzda)]_n moiety with double-chain structure cross-linking bpe spacers. However, the conformations bpe adopts in 3 and 4 are different from those in 1 and 2 due to the rotation of C-C single bond in bpe. Polymer 5 exhibits an interesting 3D porous framework with 2-fold interpenetration, in which intriguing 1D double helix chains are observed. The photoluminescence properties of 1 and 2 in the solid-state at room temperature are investigated. In addition, variable-temperature magnetic data show weak antiferromagnetic behavior in 3-5.     

Synthesis and Crystal Structure of Cobalt(II) Complex [Co(H2O)2(bpe)(OAc)2](4,4''-dpdo

The reaction of Co(OAc)2 with bpe and 4,4'-dpdo in an aqueous-alcohol solution affords the formation of red crystals of [Co(H2O)2(bpe)(OAc)2](4,4'-dpdo (bpe = trans-1,2-bis(4- pyridyl)ethylene, 4,4'-dpdo = 4,4'-dipyridyl N,N'-oxide). The molecular and crystal structures were determined by single-crystal X-ray diffraction. The crystal is of triclinic, space group P with a = 7.6146(9), b = 8.6691(11), c = 10.344011 A, α = 88.311(3), β = 76.992(3), γ = 75.809(3)°, V = 644.7613 A3, Z = 1, C26H28CoN4O8, Mr = 583.45, Dc = 1.503 g/cm3, μ = 0.724 mm-1, F(000) = 303, T = 223(2) K, the final R = 0.0477 and wR = 0.1177 for 3199 observed reflections with I > 2σ(I). In the crystal the cobalt atom is six-coordinated by oxygen atoms from two carboxylic molecules, two nitrogen atoms from the bpe ligands and two water molecules, completing an octahedral geometry. The structure of the title complex consists of neutral chains containing cobalt(II) ions bridged by mutually trans bpe molecules. The adjacent chains are connected through weak hydrogen bonds to form a two-dimensional structure.     

Structures and Reactivities of Cocrystals Involving Diboronic Acids and Bipyridines: In Situ Linker Reaction and 1D-to-2D Dimensionality Change via Crystal-to-Crystal Photodimerization

Cocrystallizations of diboronic acids [1,3-benzenediboronic acid (1,3-bdba), 1,4-benzenediboronic acid (1,4-bdba) and 4,4’-biphenyldiboronic acid (4,4’-bphdba)] and bipyridines [1,2-bis(4-pyridyl)ethylene (bpe) and 1,2-bis(4-pyridyl)ethane (bpeta)] generated the hydrogen-bonded 1 : 2 cocrystals [(1,4-bdba)(bpe)₂] (1), [(1,4-bdba)(bpeta)₂] (2), [(1,3-bdba)(bpe)₂(H₂O)₂] (3) and [(1,3-bdba)(bpeta)₂(H₂O)] (4), wherein 1,3-bdba involved hydrated assemblies. The linear extended 4,4’-bphdba exhibited the formation of 1 : 1 cocrystals [(4,4'-bphdba)(bpe)] (5) and [(4,4'-bphdba-me)(bpeta)] (6). For 6, a hemiester was generated by an in-situ linker transformation. Single-crystal X-ray diffraction revealed all structures to be sustained by B(O)−H⋅⋅⋅N, B(O)−H⋅⋅⋅O, O_w−H⋅⋅⋅O, O_w−H⋅⋅⋅N, C−H⋅⋅⋅O, C−H⋅⋅⋅N, π⋅⋅⋅π, and C−H⋅⋅⋅π interactions. The cocrystals comprise 1D, 2D, and 3D hydrogen-bonded frameworks with components that display reactivities upon cocrystal formation and within the solids. In 1 and 3, the C=C bonds of the bpe molecules undergo a [2+2] photodimerization. UV radiation of each compound resulted in quantitative conversion of bpe into cyclobutane tpcb. The reactivity involving 1 occurred via 1D-to-2D single-crystal-to-single-crystal (SCSC) transformation. Our work supports the feasibility of the diboronic acids as formidable structural and reactivity building blocks for cocrystal construction.     

Construction of an interpenetrated 3-D network by [2 + 2] cycloaddition of Zn(ClO4)2 and 1,2-trans-(4-pyridyl)ethene: counter anion effects

The reaction of Zn(ClO)2 with 1,2-trans-(4-pyridyl)ethene (bpe) results in an interpenetrated network containing both the starting bpe ligand and the newly generated 1,2,3,4-tetrakis(4-pyridyl)cyclobutane (4pycb) (formed by [2 + 2] cyclization of the starting ligand), while the reactions of Zn(NO3)2 and ZnSO4 with bpe result in a dinuclear complex and a two-dimensional sheet, respectively.     

Construction of tetranuclear macrocycles through C-H activation and structural transformation induced by [2+2] photocycloaddition reaction

A series of binuclear complexes [{Cp*Ir(OOCCH₂COO)}₂(pyrazine)] ( 1 b ), [{Cp*Ir(OOCCH₂COO)}₂(bpy)] ( 2 b ; bpy=4,4′‐bipyridine), [{Cp*Ir(OOCCH₂COO)}₂(bpe)] ( 3 b ; bpe=trans‐1,2‐bis(4‐pyridyl)ethylene) and tetranuclear metallamacrocycles [{(Cp*Ir)₂(OOC‐C?C‐COO)(pyrazine)}₂] ( 1 c ), [{(Cp*Ir)₂(OOC‐C?C‐COO)(bpy)}₂] ( 2 c ), [{(Cp*Ir)₂(OOC‐C?C‐COO)(bpe)}₂] ( 3 c ), and [{(Cp*Ir)₂[OOC(H₃C₆)‐N?N‐(C₆H₃)COO](pyrazine)}₂] ( 1 d ), [{(Cp*Ir)₂[OOC(H₃C₆)‐N?N‐(C₆H₃)COO](bpy)}₂] ( 2 d ), [{(Cp*Ir)₂[OOC(H₃C₆)‐N?N‐(C₆H₃)COO](bpe)}₂] ( 3 d ) were formed by reactions of 1 a – 3 a {[(Cp*Ir)₂(pyrazine)Cl₂] ( 1 a ), [(Cp*Ir)₂(bpy)Cl₂] ( 2 a ), and [(Cp*Ir)₂(bpe)Cl₂] ( 3 a )} with malonic acid, fumaric acid, or H₂ADB (azobenzene‐4,4′‐chcarboxylic acid), respectively, under mild conditions. The metallamacrocycles were directly self‐assembled by activation of C? H bonds from dicarboxylic acids. Interestingly, after exposure to UV/Vis light, 3 c was converted to [2+2] cycloaddition complex 4 . The molecular structures of 2 b , 1 c , 1 d , and 4 were characterized by single‐crystal x‐ray crystallography. Nanosized tubular channels, which may play important roles for their stability, were also observed in 1 c , 1 d , and 4 . All complexes were well characterized by ¹H NMR and IR spectroscopy, as well as elemental analysis.     

Structural analyses and magnetic properties of 3D coordination polymeric networks of nickel(II) maleate and manganese(II) adipate with the flexible 1,2-bis(4-pyridyl)ethane ligand

Two novel inorganic-organic hybrid 3D extended networks of Ni(II) and Mn(II) having molecular formulas [(maleate)(2)Ni(3)(bpe)(4)(H(2)O)(4)](NO(3))(2).H(2)O (1) and [(adipate)Mn(bpe)] (2) (bpe = 1, 2-bis(4-pyridyl)ethane), respectively, have been synthesized and characterized by single-crystal X-ray diffraction studies and low-temperature (300-2 K) magnetic measurements. Compound 1 crystallizes in the monoclinic system, space group C2/c (No. 15), with chemical formula C(56)H(62)N(10)Ni(3)O(19), a = 30.955(4) A, b = 12.705(3) A, c = 17.058(5) A, beta = 117.26(2) degrees, and Z = 4. Compound 2 crystallizes in the triclinic system, space group Ponemacr; (No. 2), with chemical formula C(18)H(20)MnN(2)O(4), a = 8.492(2) A, b = 9.444(2) A, c = 11.533(3) A, alpha = 97.19(1) degrees, beta = 94.64(1) degrees, gamma = 105.02(1) degrees, and Z = 2. The structure determination reveals for both a 3D network. Compound 1 contains two crystallographically independent Ni(II) ions in different octahedral environments. Ni(1) lies on an inversion center, and its coordination environment comprises two chelating maleate anions and two bpe nitrogen donors, while the Ni(2) ion is surrounded by meridionally disposed three bpe N atoms, two water molecules, and one oxygen donor from the dicarboxylate anion. Of the three crystallographic independent bpe ligand, one presents an anti and the others a gauche conformation. The corresponding N-to-N distances are 9.344, 6.543, and 6.187 A. Variable-temperature magnetic susceptibility measurement of the complex reveals the existence of a dominant ferromagnetic interaction within the molecule. Compound 2 is composed of Mn(2) dimer units linked by adipate anions to form corrugated 2D sheets which, on interconnection through bpe (anti conformation, N-to-N distance of 9.391 A), produces an interpenetrated 3D alpha-polonium-related type net. Complex 2 reveals to be antiferromagnetic fitting data using a dimeric Mn(II) model that considers negligible magnetic transmission through the carbon skeleton of adipate and the bpe pathway.     

Thermal-, pressure-, and light-induced spin transition in novel cyanide-bridged FeII-AgI bimetallic compounds with three-dimensional interpenetrating double structures (FeIILx[Ag(CN)2]2).G

Low-spin, high-spin and spin-transition behaviours have been observed for the doubly interpenetrating three-dimensional bimetallic compounds (FeII(pz)[Ag(CN)2]2).pz (pz = pyrazine), (FeII(4,4'-bipy)2[Ag(CN)2]2) (4,4'-bipy = 4,4'-bipyridine), and (FeII(bpe)2[Ag(CN)2]2) (bpe = bispyridylethylene), respectively. The single crystals of the bpe derivative undergo a spin transition with a large hysteresis loop at about 95 K. After several warming and cooling cycles, the single crystals become a microcrystalline powder with 50% spin transition. Influence of pressure--as well as light-induced excited spin-state trapping (LIESST) on the thermal 50% spin transition of the microcrystalline sample has also been investigated. Thermal spin-transition behaviour has also been induced at pressures higher than 1 bar for the 4,4'-bipy derivative. Both the 4,4'-bipy and bpe derivatives show strong pressure dependence of the spin state at 300 K.     

Interdigitation, interpenetration and intercalation in layered cuprous tricyanomethanide derivatives

Reaction of Cu(I), tricyanomethanide (tcm , C(CN)3-) and L = either hexamethylenetetramine (hmt), 4,4'-bipyridine (bipy) or 1,2-bis(4-pyridyl)ethene (bpe) gives crystals of [Cu(tcm)(hmt)] (1), [Cu(tcm)(bipy)] (2) and [Cu(tcm)(bpe)] x 0.25 bpe x 0.5 MeCN (3), respectively. Crystal structure analysis shows 1-3 all contain closely related puckered (4,4) sheets composed of tetrahedral Cu(I) ions bridged by 2-connecting tcm- and L. The crystal packing, however, varies markedly with L. In 1 the sheets interdigitate in pairs. In 2 the sheets participate in parallel interpenetration in pairs. In 3 guest bpe and MeCN molecules are intercalated in channels formed by the stacking of the sheets.     

A fourfold interpenetrating diamondoid three‐dimensional coordination polymer: poly[[[μ2‐1,2‐bis(pyridin‐4‐yl)ethene‐κ2N:N′](μ2‐5‐hydroxyisophthalato‐κ2O1:O3)zinc(II)] 1,2‐bis(pyridin‐4‐yl)ethene hemisolvate]

In the title compound, {[Zn(C₈H₄O₅)(C₁₂H₁₀N₂)]·0.5C₁₂H₁₀N₂}_n or {[Zn(HO‐BDC)(bpe)]·0.5bpe}_n [HO‐H₂BDC is 5‐hydroxyisophthalic acid and bpe is 1,2‐bis(pyridin‐4‐yl)ethene], the asymmetric unit contains a Zn^II atom, one HO‐BDC ligand, one coordinated bpe ligand and half a noncoordinating bpe molecule with crystallographic inversion symmetry. Each Zn^II centre is four‐coordinated by two O atoms from two distinct HO‐BDC ligands and two N atoms from two different bpe ligands in a ZnO₂N₂ coordination environment. The three‐dimensional topology of the title compound corresponds to a fourfold interpenetrating diamondoid coordination polymer network, with the uncoordinated bpe ligands located in the cavities, hydrogen bonded to the main network via the hydroxy group of the HO‐H₂BDC ligand.     

Syntheses,Structures, and Luminescent Properties of Two Isostructural 3D CdII Frameworks based on Rigid-flexible Hybrid Ligands

Two isostructural Cd^II frameworks, [Cd₂(MMA)₂(bpy)(H₂O)₂]_n ( 1 ) and [Cd₂(MMA)₂(bpe)(H₂O)₂]_n ( 2 ), were synthesized solvothermally with hybrid flexible methylmalonic acid (H₂MMA) and rigid 4,4'-bipyridine (bpy) or trans-1,2-bis(4-pyridyl)ethylene (bpe) as coligands. Single-crystal X-ray diffraction analyses reveal that complexes 1 and 2 display a three-dimensional (3D) framework structure composed of 2D [Cd(MMA)] layer unit and bpy/bpe linker, and exhibit a (3,4)-connected topological network with Schläfli symbol of {6³}{6⁵.8}. The solid-state luminescent properties were studied, and 1 and 2 show a distinct emission centered at 465 and 531 nm, respectively.     

Mixed-ligand complexes with trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene terminal and different aromatic polycarboxyl linkers: Synergistic modulation of metallosupramolecular architectures via coordinative and secondary interactions

A series of Co^II, Ni^II, and Cu^II complexes with trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene (bpe) and various polycarboxyl co-ligands have been prepared under general condition and characterized by IR, elemental analysis, and TG-DTA techniques. Single-crystal X-ray diffraction indicates that these complexes display multifarious binuclear, 1-D, and 2-D coordination motifs in virtue of the bridging polycarboxyl building blocks, in which the bpe ligand uniformly adopts the unidentate coordination by using its 4-pyridyl group. Remarkably, higher-dimensional extended networks are further formed with the aid of additional secondary interactions based on bpe (such as H-bonding and π–π stacking). These results demonstrate that bpe is a reliable bifunctional tecton to construct diverse supramolecular architectures via synergistic effect of multiple intermolecular interactions.     

[Hg2(μ‐bpe)(μ‐OAc)2(μ‐SCN)2]n,a New Two‐Dimensional Coordination Polymer Involving Three Simultaneously Bridging Ligands: 1,2‐Bis(4‐pyridyle)ethene,Acetate, and Thiocyanate

A new mercury(II) complex of 1,2‐bis(4‐pyridyle)ethene (bpe) with anionic acetate and thiocyanate ligands has been synthesized and characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy. The single crystal X‐ray analysis shows that the complex is a two‐dimensional polymer with simultaneously bridging 1,2‐bis(4‐pyridyle)ethane, acetate and thiocyanate ligands and basic repeating dimeric [Hg₂(μ‐bpe)(μ‐OAc)₂(μ‐SCN)₂] units. The two‐dimensional system forms a three‐dimensional network by packing via π‐π stacking interactions.     

Poly[μ2‐trans‐1,2‐di‐4‐pyridylethyl­ene‐κ2N:N′‐μ2‐sulfato‐κ2O:O′‐zinc(II)]

The title compound, [Zn(SO₄)(C₁₂H₁₀N₂)]_n, features a layered structure based on [Zn(SO₄)]_n spirals linked by 1,2‐di‐4‐pyridylethyl­ene (bpe) ligands, with the tetra­hedral Zn and S atoms lying on twofold axes. The bpe ligands are centrosymmetric. The layers are linked by weak C—H⋯O inter­actions.     

具有纳米孔结构的配位聚合物[Co2(HO-BDC)2(bpe)2(H2O)2]n·n(py)·nH2O的合成、晶体结构与热稳定性

在水-吡啶混合体系中, 以5-羟基-1,3-苯二甲酸(简作HO-H2BDC )、1,2-二(4-吡啶)乙烷(简作bpe)为配体与Co(NO3)2·6H2O反应, 培养出[Co2(HO-BDC)2(bpe)2(H2O)2]n·n(py)·nH2O(py=pyridine)的紫色单晶, 该晶体属三斜晶系, P1空间群, 晶胞参数a=1.0245(3) nm, b=1.1467(3) nm, c=1.2430(4) nm, α=68.915(5)°, β=67.163(4)°, γ=71.373(4)°, V=1.2279(6) nm3, Z=1, Mr=979.70, Dc=1.325 Mg/m3, F(000)=506, μ=0.740 mm-1, R1=0.0515, wR2=0.1058. 该配位聚合物中在ac平面上具有规则平行四边形纳米尺寸的孔, 其孔径大小约为1.025 nm×1.354 nm, 而且通过氢键相互作用连成具有双层结构的2D网络结构. TGA曲线表明, 配位聚合物的失重发生在110~150 ℃之间, 总失重约为80.1%, 最终产物为Co2O3.     

新型一维钼氧链超分子化合物[(H2bpe)Mo4O13]的合成与光学性质研究

A new 1D compound [(H₂bpe)Mo₄O₁₃](1) (bpe=trans-1,2-Di-(4-pyridyl)-ethylen) was hydrothermally synthesized and characterized. Compound 1 comprises 3D supramolecular network constructed from 1D [Mo₄O₁₃]^2- anion chains and protonated bpe layers via hydrogen bonds and π-π stacking interactions. The crystal data are the following: C₁₂H₁₂Mo₄N₂O₁₃, Monoclinic, space group P2₁/n, a=0.968 64(13) nm, b=1.349 68(18) nm, c=1.514 9(2) nm, β=99.766(2)°, Z=4. The inorganic chain built up from only molybdenum oxide building blocks is interesting. The luminescent property of 1 was studied. CCDC: 739954.