Tetrameric Clusters Research Articles

Growth pattern and electronic properties of acetonitrile clusters: A density functional study

We report a systematic theoretical study on the growth pattern and electronic properties of acetonitrile clusters [(CH(3)CN)(n) (n = 1, 9, 12)] using density functional approach at the B3LYP6-31++G(d,p) level. Although we have considered a large number of configurations for each cluster, the stability of the lowest energy isomer was verified from the Hessian calculation. It is found that the lowest energy isomer of the dimer adopts an antiparallel configuration. For trimer and tetramer, cyclic ring structures were found to be favored over the dipole stabilized structure. In general, it is found that the intermolecular CH...N interactions play a significant role in the stabilization of the cyclic layered geometry of acetonitrile clusters. A critical comparison between trimer and tetramer clusters suggests that the three member cyclic ring is more stable than four member rings. The growth motif for larger clusters (n = 5-9, 12) follows a layered pattern consisting of three or four membered rings, which, in fact, is used as the building block. Based on the stability analysis, it is found that clusters with an even number of molecular entities are more stable than the odd clusters, except trimer and nonamer. The exceptional stability of these two clusters is attributed to the formation of trimembered cyclic rings, which have been found to form the building blocks for larger clusters.

Asymmetric Pentameric and Tetrameric Organooxotin Clusters: Insights into Their Formation through Partial Dearylation

The reaction between diphenyltin dichloride and 2,6-diisopropylphenylphosphate (dippH2) in ethanol affords a highly asymmetric pentameric organotin cluster, [Sn5Ph7(μ3-dipp)4(μ-dippH)(μ3-O)(μ-OEt)(EtOH)(H2O)Cl]·H2O (1), that contains Ph−, EtO−, Cl−, O2−, ROPO32−, ROPO3H−, OH2, and EtOH ligands. The same reaction when carried out in iPrOH, under otherwise identical conditions, results in the formation of another pentamer, [Sn5Ph7(μ3-dipp)4(μ-dippH)(μ3-O)(μ-OH)(iPrOH)(H2O)Cl]·iPrOH (2). Change of the phosphate ligand to sterically less bulky 2,6-dimethylphenylphosphate in the above reaction carried out in ethanol results in the formation of a tetrameric cluster, [Sn4Ph5(μ3-dmpp)2(μ-dmpp)(μ-dmppH)2(μ3-O)(μ-OEt)(EtOH)]·EtOH (3). Isolation of 3 provides useful insights into the formation of the pentamers 1 and 2. Compounds 1−3 have been characterized by means of their analytical data, IR, and multinuclear NMR (1H, 31P, and 119Sn) spectral data. The solid-state structures of 1−3 have been determined by X-ray diffraction studies.

Synthesis and Structural Characterization of a Tetrameric Ammonium Chloride Cluster

AbstractHerein we report the synthesis and structural characterization of a derivative of the molecular cluster [NH4Cl]4. The N and Cl atoms in this compound are located at alternating corners of a slightly distorted cube in the crystal phase and are bound together through N–H···Cl bridges. This structure is in good agreement with quantum chemical calculations carried out for the [NH4Cl]4 tetramer. ESI mass spectra recorded for the compound dissolved in different solvents indicate that the cluster is stable in relatively apolar solvents such as CH2Cl2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Structural Diversity in Organotin Compounds Derived from Bulky Monoaryl Phosphates: Dimeric, Tetrameric, and Polymeric Tin Phosphate Complexes

AbstractMonoaryl phosphates with a bulky aryl substituent have been used to synthesize new organotin clusters and polymers. The equimolar reaction between 2,6‐diisopropylphenylphosphate (dipp‐H2) and Me2SnCl2 in ethanol at 25 °C leads to the formation of [Me2Sn(μ3‐dipp)]n (1), while the reaction of 2,6‐dimethylphenylphosphate (dmpp‐H2) with Me2SnCl2 in either a 1:1 or 2:1 molar ratio proceeds to produce exclusively [Me2Sn(μ‐dmpp‐H)2]n·nH2O (2). Compounds 1 and 2 are 1D polymers with different architectures. In compound 1, the tin atom is five‐coordinate (trigonal bipyramidal). Each dipp ligand bridges three different tin atoms to form an infinite ladder‐chain structure. In 2, each six‐coordinate (octahedral) tin atom is surrounded by four phosphate oxygen atoms originating from four different bridging dmpp‐H ligands, thus forming a spirocyclic coordination polymeric chain. The use of nBu2SnO as the diorganotin source in its reaction with dipp‐H2 leads to the isolation of dimeric [nBu2Sn(μ‐dipp‐H)(dipp‐H)]2 (4), which contains a central Sn2O4P2 unit. There are two chemically different half molecules of 4 in the asymmetric part of the unit cell and hence it actually exists as a 1:1 mixture of [nBu2Sn(μ‐dipp‐H)(dipp‐H)]2 and [nBu2Sn(μ‐dipp)(dipp‐H2)]2 in the solid state. The reaction of the monoorgano tin precursor nBuSn(O)(OH)·xH2O with dipp‐H2 takes place in acetone at room temperature to yield the tetrameric cluster 5, which has different structures in the solution and in the solid state. 31P NMR spectroscopy clearly suggests that 5 has the formula [nBu4Sn4(μ‐O)2(μ‐dipp‐H)8] in solution. The single‐crystal X‐ray diffraction studies in the solid state, however, reveal that compound 5 exists as [nBu4Sn4(μ‐OH)2(μ‐dipp‐H)6(μ‐dipp)2]. The use of compounds 1–4 as possible precursors for the preparation of ceramic tin phosphate materials has been investigated. The thermolysis of 1 at 500 °C leads to the formation of quantitative amounts of Sn2P2O7, while the thermolysis of 2, 3, and 4 under similar conditions results in the formation of SnP2O7. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Structural and magnetic isomers ofM(BN)36andM4(BN)36clusters(M=Ti,V,Cr,Mn,Fe,Co,Ni,Cu): Anab initiodensity functional study

Using the plane wave based pseudopotential method under the density functional formalism, the geometry and electronic structures of $M$ and ${M}_{4}$ encaged ${(\mathrm{B}\mathrm{N})}_{36}$ clusters have been investigated, where $M$ represents Ti, V, Cr, Mn, Fe, Co, Ni, and Cu atoms. The lowest energy structure of the $M{(\mathrm{B}\mathrm{N})}_{36}$ cluster shows that the impurity atom prefers to occupy either the center or off-center and close to the hexagonal ring of the cage. Geometry and electronic structures of ${M}_{4}$ clusters have been calculated in the bare state as well as inside the octahedral ${(\mathrm{B}\mathrm{N})}_{36}$ cluster. For free ${M}_{4}$ clusters, except ${\mathrm{Cu}}_{4}$, which forms a planar rhombus structure, all other tetramer clusters adopt three dimensional bent rhombus or tetrahedron configuration. In sharp contrast, the equilibrium structure of ${M}_{4}$ clusters inside the ${(\mathrm{B}\mathrm{N})}_{36}$ cage results in significant deformation in comparison to that in the free state. Unlike others, it is found that the stability of ${\mathrm{V}}_{4}$, ${\mathrm{Fe}}_{4}$, ${\mathrm{Co}}_{4}$, and ${\mathrm{Ni}}_{4}$ tetramers have been enhanced inside the cage. Importantly, these small clusters are found to retain their magnetic nature even after encaging them inside the ${(\mathrm{B}\mathrm{N})}_{36}$ cluster. In general, the magnetic moment of the ${M}_{4}$ clusters are found to decrease inside the ${(\mathrm{B}\mathrm{N})}_{36}$ cage, except that for ${\mathrm{Cr}}_{4}$ cluster, which showed significant increase in the magnetic moment. The electronic density of state analysis of these systems shows additional electronic states in the large gap of ${(\mathrm{B}\mathrm{N})}_{36}$ cluster originated by the $M$ atoms or ${M}_{4}$ clusters.

A self-assembled tetrameric water cluster stabilized by the hexachlororhenate(IV) anion and diprotonated 2,2′-biimidazole: X-ray structure and magnetic properties

A self-assembled tetrameric water cluster stabilized by [ReCl6]2− anions and [H4biim]2+ cations occurs in the new compound [H4biim][ReCl6]·4H2O, which exhibits a weak ferromagnetic coupling between the Re(IV) centers through an unusual ReIV–Cl⋯(H2O)⋯Cl–ReIV pathway.

A Combination of Lacunary Polyoxometalates and High‐Nuclear Transition‐Metal Clusters under Hydrothermal Conditions. Part II: From Double Cluster, Dimer, and Tetramer to Three‐Dimensional Frameworks

The hydrothermal reactions of trivacant Keggin A-alpha-XW(9)O(34) polyoxoanions (X=P(V)/Si(IV)) with transition-metal ions (Ni(II)/Cu(II)/Fe(II)) in the presence of amines result in eight novel high-nuclear transition-metal-substituted polyoxotungstates [{Ni(7)(mu(3)-OH)(3)O(2)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))][{Ni(6)(mu(3)-OH)(3)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))][Ni(dap)(2)(H(2)O)(2)]4.5 H(2)O (1), [Cu(dap)(H(2)O)(3)](2)[{Cu(8)(dap)(4)(H(2)O)(2)}(B-alpha-SiW(9)O(34))(2)]6 H(2)O (2), (enH(2))(3)H(15)[{Fe(II) (1.5)Fe(III) (12)(mu(3)-OH)(12)(mu(4)-PO(4))(4)}(B-alpha-PW(9)O(34))(4)]ca.130 H(2)O (3), [{Cu(6)(mu(3)-OH)(3)(en)(3) (H(2)O)(3)}(B-alpha-PW(9)O(34))]7 H(2)O (4), [{Ni(6)(mu(3)-OH)(3)(en)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))]7 H(2)O (5), [{Ni(6)(mu(3)-OH)(3)(en)(2)(H(2)O)(8)}(B-alpha-PW(9)O(34))]7 H(2)O (6), [{Ni(6)(mu(3)-OH)(3)(dap)(2)(H(2)O)(8)}(B-alpha-PW(9)O(34))] 7 H(2)O (7), and [{Ni(6)(mu(3)-OH)(3)(en)(3)(H(2)O)(6)}(B-alpha-SiW(9)O(34))][Ni(0.5)(en)] 3.5 H(2)O (8) (en=ethylenediamine, dap=1,2-diaminopropane). These compounds have been structurally characterized by elemental analyses, IR spectra, diffuse reflectance spectra, thermogravimatric analysis, and X-ray crystallography. The double-cluster complex of phosphotungstate 1 simultaneously contains hepta- and hexa-Ni(II)-substituted trivacant Keggin units [{Ni(7)(mu(3)-OH)(3)O(2)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))](2-) and [{Ni(6)(mu(3)-OH)(3)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))]. The dimeric silicotungstate 2 is built up from two trivacant Keggin [B-alpha-SiW(9)O(34)](10-) fragments linked by an octa-Cu(II) cluster. The main skeleton of 3 is a tetrameric cluster constructed from four tri-Fe(III)-substituted [Fe(III) (3)(mu(3)-OH)(3)(B-alpha-PW(9) O(34))](3-) Keggin units linked by a central Fe(II) (4)O(4) cubane core and four mu(4)-PO(4) bridges. Complex 4 is an unprecedented three-dimensional extended architecture with hexagonal channels built by hexa-Cu(II) clusters and trivacant Keggin [B-alpha-PW(9)O(34)](9-) fragments. The common feature of 5-8 is that they contain a B-alpha-isomeric trivacant Keggin fragment capped by a hexa-Ni(II) cluster, very similar to the hexa-Ni(II)-substituted trivacant Keggin unit in 1. Magnetic measurements illustrate that 1, 2, and 5 have ferromagnetic couplings within the magnetic metal centers, whereas 3 and 4 reveal the antiferromagnetic exchange interactions within the magnetic metal centers. Moreover, the magnetic behavior of 4 and 5 have been theoretically simulated by the MAGPACK magnetic program package.

Combination of Lacunary Polyoxometalates and High-Nuclear Transition-Metal Clusters under Hydrothermal Conditions. 5. A Novel Tetrameric Cluster of [{FeIIFeIII12(μ3-OH)12(μ4-PO4)4}(B-α-PW9O34)4]22-

A novel tetrameric cluster, (enH2)3.5H15[{FeIIFeIII12(mu3-OH)12(mu4-PO4)4}(B-alpha-PW9O34)4].83H2O (1; en = ethylenediamine), has been hydrothermally synthesized and characterized by IR, optical diffuse reflectance, thermogravimetric analysis, and single-crystal X-ray diffraction. The skeleton of 1 is composed of four tri-FeIII-substituted [FeIII3(mu3-OH)3(B-alpha-PW9O34)]3- Keggin moieties fused together through a FeII2O2 unit and four mu4-PO4 bridges, resulting in a unique tetramer with C2 symmetry. Magnetic measurements indicate that 1 reveals the antiferromagnetic interactions between FeII and FeIII centers.

A novel 3D supramolecular inorganic–metal–organic architecture with honeycomb-like motifs directed by the water tetramer and sulfate anion

Rectangle-like tetrameric water clusters associate with sulfate anions and coordinated water molecules into a 2D honeycomb-like layer via hydrogen-bonded interactions. The 2D layer acts as “host” supporting the metal–organic “guest” into a 3D supramolecular architecture.

Synthesis and Crystal Structure of New Early‐Lanthanide Organometallic Clusters

AbstractReaction of Cp*2NdCl·LiCl·2thf (1) with excess catecholborane affords the hexameric cluster (Cp*NdCl2)6(LiCl)3(thf)3 (2) bearing three types of bridging chloride ions. Heating the reaction mixture affords the tetrameric cluster [(Cp*NdCl2)4(μ4‐Cl)]2[LiO2][LiO2*Li2O*O2] (3), which has the first crystal structure with the LiO2+ motif. Reaction of complex 1 or the analogous Sm complex, 4, with pinacolborane affords clusters 5a (Nd) or 5b (Sm), respectively, a second type of hexameric cluster built from two CpNd3Cl5(thf) units bonded by two μ2‐Cl atoms. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Stabilisation of reactive intermediates in molecular sieves

This paper presents studies on paramagnetic intermediates, free atoms and radicals produced in γ-irradiated molecular sieves and their reactions with adsorbate molecules or exchangeable cations. Four different systems have been investigated using EPR spectroscopy, Na-A/CH4, AgNa-A/CH3OH, Ag-SAPO-11/C2H4 and AgCs-rho/NH3. It was found that methyl radicals are formed in two different sites in Na-A/CH4 and in one of them they are stable at room temperature. The formation of Ag·CH2OH+ radical cation with one-electron bond between silver and carbon has been established in AgNa-A/CH3OH by EPR experiments with [13C]CH3OH and DFT calculations. In Ag-SAPO-11/C2H4 the stabilisation of biligand silver/ethylene complex, Ag0(C2H4)2 was postulated based on EPR and DFT results. Tetrameric silver clusters (Ag 4 3+ ) produced radiolytically in AgCs-rho/NH3 strongly interact with two ammonia molecules as was deduced from the changes in superhyperfine structure of high-field EPR line of Ag 4 3+ pentet for zeolite exposed to [14N]NH3 and [15N]NH3. The presented examples clearly show that the combination of radiation methods with EPR technique is very useful to study the structure and reactivity of paramagnetic intermediates.

Sodium Hydride Clusters in Solid Hydrogen and Neon: Infrared Spectra and Theoretical Calculations

Laser-ablated sodium atom reactions with H2 have been investigated in solid molecular hydrogens and neon. The NaH molecule and (NaH)2,3,4 clusters were identified by IR spectra with isotopic substitution (HD and D2) and comparison to frequencies calculated by density functional theory and the MP2 method. The use of para-hydrogen enriched samples provides evidence for a (H2)nNaH subcomplex surrounded by the solid hydrogen matrix cage. The ionic rhombic (NaH)2 dimer is characterized by strong absorptions at 761.7, 759.1, and 757.0 cm(-1), respectively, in solid neon, para-hydrogen, and normal hydrogen matrices. The cyclic sodium hydride trimer and tetramer clusters are also observed. Although the spontaneous reaction of two Li and H2 to form (LiH)2 occurs on annealing in solid H2, the formation of (NaH)2 requires near uv photoexcitation.

Infrared Spectra and Theoretical Calculations of Lithium Hydride Clusters in Solid Hydrogen, Neon, and Argon

A matrix isolation IR study of laser-ablated lithium atom reactions with H2 has been performed in solid para-hydrogen, normal hydrogen, neon, and argon. The LiH molecule and (LiH)(2,3,4) clusters were identified by IR spectra with isotopic substitution (HD, D(2), and H(2) + D(2)) and comparison to frequencies calculated by density functional theory and the MP2 method. The LiH diatomic molecule is highly polarized and associates additional H(2) to form primary (H(2))(2)LiH chemical complexes surrounded by a physical cage of solid hydrogen where the ortho and para spin states form three different primary complexes and play a role in the identification of the bis-dihydrogen complex and in characterization of the matrix cage. The highly ionic rhombic (LiH)(2) dimer, which is trapped in solid matrices, is calculated to be 22 kcal/mol more stable than the inverse hydrogen bonded linear LiH-LiH dimer, which is not observed here. The cyclic lithium hydride trimer and tetramer clusters were also observed. Although the spontaneous reaction of 2 Li and H(2) to form (LiH)(2) occurs on annealing in solid H(2), the formation of higher clusters requires visible irradiation. We observed the simplest possible chemical reduction of dihydrogen using two lithium valence electrons to form the rhombic (LiH)(2) dimer.

Supramolecular Host−Guest Systems of Luminescent Zn(II) Complexes with Benzene, Nitrobenzene, and Ethanol: Selectivity of Guest Inclusion and Solid-State Fluorescence Modulation Studies

The luminescent Zn(II) complex [Zn(phen)(aba)2] (B) {phen = 1,10-phenanthroline, aba = 4-(dimethylamino)benzoate} crystallizes as [Zn(phen)(aba)2(H2O)] (B1) from moist solvents. Compound B shows high selectivity toward benzene in the presence of other organic guests in solution as well as in the vapor phase forming {[Zn(phen)(aba)2(H2O)]·1/2C6H6}n (1). Compound 1 assumes a channel structure where benzene molecules are trapped in alternate channels via various supramolecular interactions. Compound B1, on the other hand, does not show any selectivity toward guest inclusion and readily assembles as {[Zn(phen)(aba)2(H2O)]·2C6H5NO2}n (2) in the presence of nitrobenzene or as {[Zn(phen)(aba)2(H2O)]·2C2H5OH}n (3) in the presence of ethanol. In 2, nitrobenzene molecules form zigzag tapes via C−H···O and C−H···π interactions inside the channels, while the structure of 3 looks like a two-dimensional network with voids occupied by tetrameric ethanol clusters. The three structures exhibit significantly red-shifted emission in the solid state with respect to the parent complex. In the case of 1, the desorption and resorption of benzene are thermally reversible as monitored by X-ray powder diffraction.

Alkali‐Metal Pyrazolate Complexes with Unusual Pyrazolate Coordination Modes and Pseudocubane Motifs

The dimeric complex [Li(Ph2pz)(OEt2)]2 (1) and tetrameric cluster [Na(Ph2pz)(thf)]4 (2) were prepared by treatment of alkali-metal reagents (nBuLi and Na{N(SiMe3)2}, respectively) with 3,5-diphenylpyrazole (Ph2pzH) in Et2O (1) or THF (2). The polymer [Na(tBu2pz)]n (3) was obtained from reaction at elevated temperature in a sealed tube between Na metal and 3,5-di-tert-butylpyrazole (tBu2pzH). The complex [Na4(tBu2pz)2(thf)3(obds)]2 (4; obds = (OSiMe2)2O) was obtained as a minor product from prolonged treatment of tBu2pzH with elemental sodium in a silicone-greased flask. All four alkali-metal pyrazolato complexes were characterized by IR and 1H NMR spectroscopy and X-ray crystallography.The Li dimer 1 displays mu-eta(2):eta(1) lithium-pyrazolato binding, in which both lithium atoms are four-coordinate. Room- and variable-temperature NMR studies (1H, 13C, and 7Li) of 1 suggest similar behavior in solution, with peaks coalescing at low temperatures. Complexes 2 and 4 display distorted cubane structures. In 2, all the sodium atoms are five-coordinate, whereas 4 contains two sodium/pyrazolate/thf clusters (4:2:3 ratio) bridged by two obds(2-) units, as well as two four-coordinate and two five-coordinate sodium atoms. Compound 3 is composed of two independent chains with the unusual coordination modes mu3-eta(5):eta(2):eta(2), mu3-eta(5):eta(2):eta(1), and mu3-eta(4):eta(2):eta(1), with five-, six-, and seven-coordinate sodium atoms. Two oxo-centered M8 cage complexes [(tBu2pz)6Li8O] (5) and [(tBu2pz)6Na8O] (6) were obtained as by-products from attempted preparation of [Li(tBu2pz)] and [Na(tBu2pz)], respectively, and their structures were determined.

Experimental and theoretical study of thermodynamic excess properties of associating liquid alkanol + 4-picoline mixtures based on quantum mechanical ab initio calculations

Experimental data of the molar enthalpy of mixing H m E of 6 alkanol + 4-picoline systems obtained by flow calorimetric measurements have been compared with statistical–mechanical calculations based on the ERAS-model. The original version of the model has been extended by accounting for results obtained by quantum mechanical ab initio calculations of energetic and structural properties of about 50 molecular clusters, each containing up to 4 molecules associated by hydrogen bonding. The essential results obtained from these calculations are cooperative effects concerning the hydrogen bonding energies of linearly associated alkanol clusters and the quantitative specification of particularly stabilized cyclic alkanol tetrameric clusters. Furthermore, results for the structure and energy of cross-associating clusters containing alkanols and 4-picoline molecules have revealed that the cross-associating energy of the alkanol + 4-picoline hydrogen bonding exceeds the self associating energy of alkanol molecules also leading to an additional cooperative energetic effect when more than two molecules are involved. These quantum mechanical results have directly been incorporated as molecular parameters into the extended ERAS-model without increasing the number of freely adjustable parameters compared to previous versions of the model. An excellent description of the thermodynamic mixture properties has been achieved. The molar excess enthalpy H m E is negative for all 1-alkanol + 4-picoline mixtures while isomeric 2-alkanol + 4-picoline mixtures show positive H m E values quantitatively described by the theory. An explanation of this effect is given on the basis of the ab initio results.

Ion Pair Recognition of Quaternary Ammonium and Iminium Salts by Uranyl−Salophen Compounds in Solution and in the Solid State

Efficient ditopic receptors for quaternary ammonium and iminium salts have been obtained upon functionalization of the uranyl-salophen unit with conformationally flexible side arms bearing phenyl or beta-naphthyl substituents. Binding affinities in chloroform solution have been measured for a large number of quaternary salts comprising tetramethylammonium (TMA), tetrabutylammonium (TBA), acetylcholine (ACh), N-methylpyridinium (NMP), and N-methylisoquinolinium (NmiQ) cations. Recognition of the anion partner is ensured by coordination to the hard Lewis acidic uranyl center, whereas cation-pi/CH-pi interactions of the quaternary ions are established with the aromatic pendants. The role of the cation-anion interactions on the dynamics of exchange between the free and complexed species is discussed. Solid-state structures have been obtained for a few salt-receptor combinations. In the solid state, side-armed receptor molecules form assemblies that enclose ion pair aggregates of varying composition and structure, including AChCl dimers, two different kinds of tetrameric (TMA)Cl clusters, and unidimentional salt strips of (NMP)Br. The lack of side arms as preferential binding sites for the polar quaternary cations prevents association patterns of the kinds formed with the side-armed receptors, as shown by the crystal structure of the complex of (TMA)Cl with the parent uranyl-salophen receptor.

The irreversible crystal transformation of a novel Cadmium(II) supramolecular complex containing planar tetrameric water cluster

A new cadmium complex [CdL2(CH3COO)2]·3H2O (1) has been synthesized by the reaction of 2-aminobenzimidazole (L) with cadmium acetate in an aqueous solution, and structurally characterized by single crystal X-ray diffraction and FT-IR spectra. Cyclic planar tetrameric water clusters with C2h symmetry are observed to be encapsulated in the 3D open supramolecular architecture of 1 by hydrogen bonds interactions. Interestingly, 1 can convert irreversibly into single crystal 1a formulated [CdL2(CH3COO)2] by losing its lattice water molecules at room temperature. Strong intermolecular N–H⋯O hydrogen bonds and aromatic rings π–π stacking interactions assemble 1a into another 3D interdigitated supramolecular network.

PbnI4n+2(2n+2)? ribbons (n = 3, 5) as dimensional reductions of 2D perovskite layers in cystamine cation based hybrids, also incorporating iodine molecules or reversible guest water molecules

Pb(n)I(4n+2)((2n+2)-) (n = 3, 5) ribbons, which can be regarded as dimensional reductions of 2D perovskite layers, are stabilized by diprotonated cystamine cations in (NH(3)(CH(2))(2)SS(CH(2))(2)NH(3))(4)Pb(3)I(14),I(2) (1) and (NH(3)(CH(2))(2)SS(CH(2))(2)NH(3))(6)Pb(5)I(22).4H(2)O (2). Both 1 and 2 have interesting structural characteristics; it is unprecedented that the ribbons are linked via I(2) molecules incorporated in the lattice of 1, while tetrameric water clusters are trapped in the structure of 2. 2 undergoes a (reversible) water desorption process at 310 K leading to (NH(3)(CH(2))(2)SS(CH(2))(2)NH(3))(6)Pb(5)I(22).2H(2)O (3). The electrical behavior of 2 and 3 has been investigated in the ranges 293-310 K and 310-358 K respectively. Above 310 K, the electronic contribution remains constant while the ionic transference number tends towards unity showing almost pure ionic transport at 360 K (6 x 10(-7) S cm(-1) at 330 K) originating probably from the migration of protons through the hydrogen bonds connecting the water molecules to the cystamine counter cations.

Self-Assembly of a Water Chain with Tetrameric and Decameric Clusters in the Channel of a Mixed-Valence CuICuII Complex

The reaction of Cu(BF4)2 with pyridine-2,6-dicarboxylic acid (H2pydc) and trans-1,2-bis(4-pyridyl)ethylene (bpe) under hydrothermal conditions afforded a porous mixed-valence CuICuII coordination polymer. Coexistence of tetrameric and decameric water clusters within the channels of the complex leads to a novel water chain. The metal−organic framework provides both hydrophilic and hydrophobic environments for stabilizing the clusters and retains its integrity upon dehydration and rehydration.