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Herein, the effects of the number (mono-PT and di-PT types) and different types of proton donors (hydroxyl (OH) and amino (NH2) groups) on the hydrogen bond strengths, electronic properties, and excited-state intramolecular single proton transfer (SPT) and double proton transfer (DPT) reactions in bipyridine derivatives were theoretically investigated using time-dependent density functional theory with both static calculations and dynamic simulations. The results of the static calculations show that the strength of the intramolecular hydrogen bond of all the studied molecules is stronger in the S1 state than that in the S0 state, which is supported by the red-shift in the corresponding vibrational mode and topology analysis. The effect of the number of proton donors causes the absorption peak of the mono-PT type to be blue-shifted, but its emission peak is red-shifted compared with that of the di-PT type. In contrast, the effect of different proton donors causes both the absorption and emission peaks in the molecules having OH groups to be blue-shifted compared with that with NH2 groups. The potential energy curves along the PT coordinates in the S1 state show that the mono-PT type has a lower PT barrier and are more exothermic than that of the di-PT type. The PT process in the molecules with an OH proton donor occurs easily than that in the molecules with an NH2 proton donor because of the lower PT barrier. Moreover, the 1st PT for SPT was found to be more favorable than the 2nd PT for DPT of the di-PT type due to its low PT barrier and exothermic reaction. Furthermore, the results of the dynamic simulations for the S1 state support that the occurrence of SPT and DPT is dependent on the PT barrier and reaction energy, in which the PT process is favorable with a low PT barrier and exothermic reaction but unfavorable with a high PT barrier and endothermic reaction. Therefore, the photophysical properties and PT processes of bipyridine derivatives can be tuned based on the number and type of proton donors. [ABSTRACT FROM AUTHOR]

Supramolecular self-assembly is an important strategy in nanotechnology and surface science, which has attracted extensive attention in the past decades. In this field, how to obtain more diverse two-dimensional structures and make them more stable has always been a huge challenge. Scanning Tunneling Microscopy (STM), with atomic resolution, is a unique technique for exploring supramolecular self-assembly. In this review, we present the latest progress in the development of two-dimensional (2D) nanostructures using bipyridine derivatives as ligands in our laboratory. Our focus is mainly on: (1) supramolecular coordination on the HOPG surfaces; (2) synergistic interactions of H-bonding; and (3) regulation of aromatic acid derivatives. It is worth noting that the addition of bipyridine provides a new idea and method for the construction of diverse two-dimensional self-assembly structures. [ABSTRACT FROM AUTHOR]

A series of [Pt(bpy)(qdt)] {bpy = 2,2′-bipyridine; qdt = quinoxaline-2,3-dithiolate} derivatives was chosen to study the effect of structural modifications on the optoelectronic and nonlinear optical (NLO) properties of the molecules. Here, this study examined eight bipyridine derivatives with different electron-donating and electron-withdrawing anchoring groups using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The results indicated that the electronic character of the [Pt(bpy)(qdt)] complex is sensitive to the type of anchoring groups connected to the bpy ligand. The considered electron-withdrawing anchors notably narrow the energy gap of the [Pt(bpy)(qdt)] complex in comparison to the electron-donating anchors. Interestingly, replacement of a hydrogen atom by electron-donating anchors in the [Pt(bpy)(qdt)] complex leads to high molar absorption coefficients, whilst complexes with electron-withdrawing anchors can be redshifted significantly. The values of light-harvesting efficiency (LHE) were also calculated and compared in both gas and solvent phases. Moreover, the results reveal that substituting H atoms of bpy ligand by electron-withdrawing anchors dramatically increases the static first hyperpolarizability (β0) value. We expect that the present study would deepen the understanding of electron-donating and -withdrawing anchoring groups in diimine–dithiolate complexes and may contribute to the development of potentially high performance NLO materials. [ABSTRACT FROM AUTHOR]

Thorium chalcogenolates Th(ER)4 react with 2,2′-bipyridine (bipy) to form complexes with the stoichiometry (bipy)2Th(ER)4 (E = S, Se; R = Ph, C6F5). All four compounds have been isolated and characterized by spectroscopic methods and low-temperature single crystal X-ray diffraction. Two of the products, (bipy)2Th(SC6F5)4 and (bipy)2Th(SeC6F5)4, crystallize with lattice solvent, (bipy)2Th(SPh)4 crystallizes with no lattice solvent, and the selenolate (bipy)2Th(SePh)4 crystallizes in two phases, with and without lattice solvent. In all four compounds the available volume for coordination bounded by the two bipy ligands is large enough to allow significant conformational flexibility of thiolate or selenolate ligands. 77Se NMR confirms that the structures of the selenolate products are the same in pyridine solution and in the solid state. Attempts to prepare analogous derivatives with 2,2′,6′,2′′-terpyridine (terpy) were successful only in the isolation of (terpy)(py)Th(SPh)4, the first terpy compound of thorium. These materials are thermochromic, with color attributed to ligand-to-ligand charge transfer excitations. [ABSTRACT FROM AUTHOR]

The Fe(ii) complex of the L1 ligand (L1 = 6-(3,5-diamino-2,4,6-triazinyl)-2,2′-bipyridine) has been used as a templating cation for the growth of oxalate-based networks. The magnetic characterization of the [FeII(L1)2](ClO4)2·CH3CN (1) precursor in the solid state has been performed for the first time showing that the low-spin (LS) state is predominating from 2 to 400 K with 10% of Fe(ii), which undergoes a gradual and irreversible spin-crossover above 350 K. 1 presents the LIESST effect with a photo-conversion close to 25% and a T(LIESST) of 49 K. During the preparation of 1, a secondary product of the formula [FeII(L1)(CH3CN)2(H2O)](ClO4)2·CH3CN (2) has been obtained. The magnetic characterization of 2 shows that it contains high-spin (HS) Fe(ii). 1 has afforded two novel oxalate-based compounds, the 2D compound of the formula [FeII(L1)2][MnIICrIII(ox)3]2·(CH3NO2)6·(CH3OH)·(H2O)2 (3) and the 3D compound of the formula [FeII(L1)2][MnIICrIII(ox)3]2·(CH3CN)3 (4), which have been obtained by changing the synthetic conditions. The magnetic properties show that in 3 the inserted Fe(ii) cation remains in the LS state from 2 to 340 K and presents a partial and irreversible spin-crossover of ∼20% at higher temperatures. In 4, most of the Fe(ii) complexes remain in the LS state from 2 to 230 K and present a partial and irreversible spin-crossover of ∼50% from 230 to 400 K. 3 and 4 do not present the LIESST effect. [ABSTRACT FROM AUTHOR]

The first examples of 3-D metal–organometallic networks (MOMNs) bearing 1,1′-ferrocenyldicarboxylate ligands have been obtained. These MOMNs exhibit a diamondoid-like network topology with 3-fold interpenetration described with point symbols for a net with loops, {66}{6}2. Their electrochemical properties were evaluated by solution-state differential pulse voltammetry. [ABSTRACT FROM AUTHOR]

Complexes of Co(iii) containing mixed chelating diimine and o-quinone ligand sets are of fundamental interest on account of their fascinating magnetic and electronic properties. Whilst complexes of this type containing one diimine and two o-quinone ligands have been studied extensively, those with the reverse stoichiometry (two diimines and one o-quinone) are much rarer. Herein, we describe a ready route to the synthesis of the complex [CoIII(o-catecholate) (2,2′-bipyridine)2]+ (1), and also report the synthesis of [CoIII(o-catecholate)(5,5′-dimethyl-2,2′-bipyridine)2]+ (2) and [CoIII(o-benezenedithiolate)(5,5′-dimethyl-2,2′-bipyridine)2]+ (3) for the first time. Spectroscopic studies show that complex 2 displays intriguing solvatochromic behaviour as a function of solvent hydrogen bond donation ability, a property of this type of complex which has hitherto not been reported. Time-dependent density function theory (TD-DFT) shows that this effect arises as a result of hydrogen bonding between the solvent and the oxygen atoms of the catecholate ligand. In contrast, the sulfur atoms in the benzenedithiolate analogue 3 are much weaker acceptors of hydrogen bonds from the solvent, meaning that complex 3 is only very weakly solvatochromic. Finally, we show that complex 2 has some potential as a molecular probe that can report on the composition of mixed solvent systems as a function of its absorbance spectrum. [ABSTRACT FROM AUTHOR]

The electrochemical and photochemical catalytic reductions of CO2 using N,O and N,S-NHC-containing dicarbonyl rhenium(i) bipyridine complexes have been investigated. By replacing the carbonyl ligand in tricarbonyl rhenium(i) complexes with a weaker π-accepting ligand, the characteristic MLCT transitions shifted to lower energy. This makes photocatalysts capable of harvesting low-energy visible light for catalyzing CO2 reduction. A detailed study revealed that these dicarbonyl rhenium(i) complexes are also highly selective for photocatalysis of CO2 to CO with a good quantum efficiency (10%), similar to that of the tricarbonyl rhenium(i) complex analogues. From the electrochemical study, it was observed that the catalysts efficiently produce CO from CO2 with high turnover frequency and good stability over time. [ABSTRACT FROM AUTHOR]

Two series of ternary assemblies comprising metal–salophen [salophen = N,N′-phenylenebis(salicylideneimine)] complexes (M = Zn2+ or UO22+) and 4,4′-bipyridine have been synthesized. Their absorption and emission data have been compared with those of the corresponding mononuclear derivatives. The dinuclear zinc species present lower emission intensities than those corresponding to the mononuclear precursors, while the emission of the analogous uranyl complexes is observed to increase. Absorption and emission titrations indicate that the ternary species are obtained in two independent coordination steps. The important role of the electron donating/withdrawing properties of the substituents is analyzed regarding their photophysical properties and the association constants. A MLCT transition (recorded by emission spectra) is expected and supported by the increase in the emissive properties of the complexes containing the higher electron donating substituent (methoxy). Nevertheless, this electron donating character disfavors the coordination to bipyridine as shown by the lower calculated association constants. DFT calculations have been performed on the zinc derivatives in order to estimate the relative stability of the dinuclear complexes. [ABSTRACT FROM AUTHOR]

The rate of electrocatalytic water oxidation by the heterogeneous water oxidation catalyst [Ru(bda)(4-O(CH2)3P(O3H2)2-pyr)2], 1, (pyr = pyridine; bda = 2,2′-bipyridine-6,6′-dicarboxylate) on metal oxide surfaces is greatly enhanced relative to water as the solvent. In these experiments with propylene carbonate (PC) as the nonaqueous solvent, water is the limiting reagent. Mechanistic studies point to atom proton transfer (APT) as the rate limiting step in water oxidation catalysis. [ABSTRACT FROM AUTHOR]

New ferrocenoylacetonate complexes of several rare earth elements, [Ln(fca)3(bpy)]·MeC6H5 (Ln = Pr (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6), Y (7); bpy – 2,2′-bipyridine; Hfca – FcCOCH2COMe) as well as scandium ferrocenoylacetonate [Sc(fca)3]·0.5MeC6H5 (8), were synthesized and characterized by single crystal X-ray diffraction analysis. In the crystal lattice of the isostructural complexes 1–7, two [Ln(fca)3(bpy)] molecules form a pair due to stacking interactions between the bpy ligands. The Ln3+ ions are coordinated in a square antiprism geometry with a coordination number of 8. The Sc3+ ions in complex 8 are coordinated in an octahedral geometry. Thermolysis of complexes 1–7 was studied under air and argon atmospheres; in the first case, it affords perovskites LnFeO3 as one of the products. Complexes 4–6 display single-molecule magnet properties, and the effective relaxation barrier for the Dy complex 5, was found to be Δeff/kB = 241 K, which is one of the highest values obtained for a mononuclear β-diketonate lanthanide complex. [ABSTRACT FROM AUTHOR]

The phase behaviour and spin states of [Fe(NCS)2(dpq)2] (1; dpq = dipyrido[3,2-f:2′,3′-h]quinoxaline), [Fe(NCS)2(dppz)2] (2; dppz = dipyrido[3,2-a:2′3′-c]phenazine) and [Fe(NCS)2(dppn)2] (3; dppn = dipyrido[3,2-a:2′3′-c]benzophenazine) have been investigated. Solvent-free 1 and 2 are isostructural and low-spin in the crystalline state, in contrast to previously published 2·py (py = pyridine) which exhibits a hysteretic spin-crossover (SCO) transition near 140 K. The inactivity of 1 and 2 towards SCO may relate to their more crowded intermolecular lattice environment, particularly two very short intermolecular anion…π contacts involving the NCS− ligands. Two solvate phases of 1 are also described, including 1·2py which undergoes gradual SCO with T½ca. 188 K. Bulk samples of 2 and 3 are predominantly low-spin and isostructural with the crystals of 2 by powder diffraction, but bulk samples of 1 contain an extra phase that exhibits hysteretic SCO, but was not crystallographically characterised. Crystal structures of low-spin [Fe(dppz)3][ClO4]2 (4) and a solvate of [Fe(dppn)3][BF4]2 (5) are also described, which are the first homoleptic complexes of these ligands to be crystallographically characterised. [ABSTRACT FROM AUTHOR]

Some critical issues concerning the complex synthesis and crystallization of designed coordination polymers are highlighted by using gels as diffusion media. The systematic use of gel methods in a variety of different crystallization configurations has been proven useful in revealing the field of existence and the stability hierarchy of competitive and concomitant crystalline phases, and also in discovering some important effects due to gel matrices. The most interesting phenomena observed are the modification and alteration of the macro- and microscopic morphology of crystals due to gel incorporation, which are responsible for changes in many properties and functionalities of these materials, opening up new possibilities for their applications in a variety of technological fields. In addition, a kinetic study of a gel grown polymeric system has also been conducted, demonstrating the continuous evolution of crystal morphology and its connection with the crystal growth process and growth mechanism. [ABSTRACT FROM AUTHOR]

A trinuclear ruthenium complex, 3, was designed and synthesized with the ligand 2,2′-bipyridine-6,6′-dicarboxylic acid (bda) and we found that this complex could function as a highly efficient molecular catalyst for water oxidation in homogeneous systems. This trinuclear molecular water oxidation catalyst, 3, displayed much higher efficiencies in terms of turnover numbers and initial oxygen evolution rate than its counterparts, a binuclear catalyst, 2, and a mononuclear catalyst, 1, in both chemically driven and photochemically driven water oxidation based on either the whole catalytic molecules or just the active Ru centers. The reasons for the superior performance of catalyst 3 were discussed and we believe that multiple Ru centers in a single molecule are indeed beneficial for increasing the probability of the formation of O–O bonds through an intramolecular radical coupling pathway. [ABSTRACT FROM AUTHOR]

A new single-component photocatalyst for the reduction of water to H2, a dichloro(dpbpy)platinum(ii) derivative (dpbpy = 4,4′-diphenyl-2,2′-bipyridine) tethered to four pendant viologen acceptors (1), is shown to exhibit twice higher photocatalytic efficiency than the previously reported dichloro(bpy)-platinum(ii) analog (2; bpy = 2,2′-bipyridine), consistent with the higher absorptivity of 1 at the metal-to-ligand charge transfer (1MLCT) band due to the larger π-conjugation in dpbpy relative to bpy. [ABSTRACT FROM AUTHOR]

Three low-dimensional Cu(ii)-based organophosphonates were synthesized: two molecular cationic complexes, [Cu2(μ2-L)2(2,2′BPy)2(H2O)2](NO3)2·S (1) and [Cu(L)(2,2′BPy)2]·NO3·(H2O)2 (3), and one neutral complex, [Cu2(μ2-L)2(2,2′BPy)2(NO3)2]·MeOH (2), assembled by the phosphonomonoester i.e., ethylhydrogen(anthracen-9-ylmethyl)phosphonate and an auxillary bidendate ligand (2,2′-bipyridine). Single-crystal X-ray diffraction analysis showed that complex 1 consisted of a dimer unit arranged supramolecularly with a nitrate anion and that these layers were further assembled viaπ…π interactions, which resulted in the formation of a porous supramolecular architecture. The cationic complexes 1 and 3 showed supramolecular templated assembly by simply altering the solvent, which resulted in a change in architecture. The remarkable change from a cationic complex to a neutral complex via the formation of an amorphous solid (1a) (a crystal–amorphous–crystal transformation) was observed when crystals of 1 were heated at 90 °C under vacuum. It is hypothesized that the uncoordinated nitrate ion moved from the lattice to the metal, resulting in the transformation of the cationic metal complex into a neutral metal complex. These complexes also showed luminescent behaviour. [ABSTRACT FROM AUTHOR]

A series of platinum(ii) biphenyl 2,2′-bipyridine complexes containing electron-donating and electron-withdrawing moieties on the 4 and 4′ positions of the bipyridine ligand exhibit emission from excited states in the 600 nm region of the spectrum upon excitation in the metal-to-ligand charge transfer transition located near 450 nm. These complexes are distorted from planarity based on both single crystal structure determinations and density functional theory (DFT) calculations of isolated molecules in acetonitrile. The DFT also reveals the geometry of the lowest-lying triplet state (LLTS) of each complex that is important for emission behavior. The LLTS are assigned based on the electron spin density distributions and correlated with the singlet excited states to understand the mechanism of electronic excitation and relaxation. Time-dependent DFT calculations are performed to compute the singlet excited state energies of these complexes so as to help interpret their UV-Vis absorption spectra. Computational and experimental results, including absorption and emission energy maxima, electrochemical reduction potentials, LLTS, singlet excited states, and LUMO and HOMO energies, exhibit linear correlations with the Hammett constants for para-substituents σp. These correlations are employed to screen complexes that have not yet been synthesized. The correlation analysis indicates that the electronic structure and the HOMO–LUMO energy gap in Pt(ii) complexes can be effectively controlled using electron-donating and electron-withdrawing moieties covalently bonded to the ligands. The information presented in this paper provides a better understanding of the fundamental electronic and thermodynamic behavior of these complexes and could be used to design systems with specific applications. [ABSTRACT FROM AUTHOR]

Determining the mechanism of metal–organic framework (MOF) crystal growth is important for the development of more efficient and reliable synthetic methods. Resonance Raman spectroscopy has been used for the first time to detect interactions in solution between metal ions and bridging ligands as MOFs form. UV excitation (229 nm) produced strong resonance enhancement of 4,4′-bipyridine (bpy) vibrational bands and showed that soluble Co2+-bpy species formed in solution prior to the growth of MOF crystals from bpy and Co(NO3)2. The results of the Raman experiments informed the development of faster methods for synthesizing [Co2(bpy)3(NO3)4]n 2D bilayer and [Co(bpy)(NO3)2(H2O)2]n 1D chain MOFs. [ABSTRACT FROM AUTHOR]

A 2,2′-bipyridine-appended ferrocene rotor, 1,1′-di(5-yl-ethynyl-2,2′-bipyridine)ferrocene, can be switched from a folded/stacked (syn) conformation to an extended/unstacked (anti) conformation by the addition of [Cu(CH3CN)4](PF6) and 6,6′-dimesityl-2,2′-bipyridine. This extension and contraction process was completely reversible and could be triggered either chemically or electrochemically. [ABSTRACT FROM AUTHOR]

Complexation of two types of dicationic bipyridium guests, paraquat derivatives and bis(N-mono-substituted bipyridine) cations, by a negatively charged carboxylato-biphen[3]arene (CBP3) in water is reported. CBP3 could strongly interact with these guests, where charge-transfer and electrostatic interactions play important roles. [ABSTRACT FROM AUTHOR]

A new series of photoactive metallocyclodextrins with increased fluorescence intensity upon binding with ssDNAs/aptamers has been demonstrated to sensitively and selectively detect lysozyme. The detection mechanism relies on the formation of an aptamer–lysozyme complex, which leads to reduction of fluorescence intensity. [ABSTRACT FROM AUTHOR]

The incorporation of a rhenium atom within an extended helical π-conjugated bi-pyridine system impacts the chiroptical and photophysical properties of the resulting neutral or cationic complexes, leading to the first examples of rhenium-based phosphors that exhibit circularly polarized luminescence. [ABSTRACT FROM AUTHOR]

We present the study of nano- and microparticles of the Fe(Me2-bpy)2(NCSe)2 spin-crossover complex prepared from the diamagnetic precursor [Fe(Me2-bpy)3](NCSe)2·S. Two solvates of the latter were characterized by single-crystal X-ray structures at 100 K (S = 2MeOH or 3H2O). The extraction of one Me2-bpy per metal ion in [Fe(Me2-bpy)3](NCSe)2·S was achieved either by thermolysis at temperature higher than 150 °C or by precipitation in an anti-solvent, leading to a polycrystalline or particulate powder of Fe(Me2-bpy)2(NCSe)2. This chemical conversion was investigated by TGA, powder X-ray diffraction, IR, Raman and magnetic measurements. The S = 0 ↑S = 2 spin-crossover of Fe(Me2-bpy)2(NCSe)2 centered at ca. 340 K is almost complete at low temperature (HS residue ≤ 5% below 250 K) while at 370 K, the HS fraction can be estimated at ∼0.7. These features are essentially preserved whatever be the size of particles (56, 460 and 1200 nm) as a consequence of the weak cooperativity of the process occurring at high temperature, the crystallinity and the molecular nature of particles. This approach leading to dispersion of small particles in a polymer is suitable for the preparation of materials of optical quality, via the stabilization and processing of nanoparticles in convenient matrices to form thin films. [ABSTRACT FROM AUTHOR]

Theoretical calculations (density functional theory with the scalar relativistic ZORA Hamiltonian) have been performed to obtain the energy and Gibbs free energy of formation of cationic 1 : 3 complexes of americium(iii) and europium(iii) with a tri-O-dentate diglycolamide ligand TEDGA (a model of TODGA extractant), as well as the free energy of their partition between water and an organic diluent. The distribution of electron density over the atoms, bonds, and molecular orbitals was analyzed by means of Mulliken population analysis, the localization procedure of natural bond orbitals, and the Quantum Theory of Atoms-in-Molecules. The stabilities of both [M(TEDGA)3]3+ complexes are similar to each other. On the other hand, our recent data for a similar pair of cationic Am/Eu complexes with a softer (HSAB) tetra-N-dentate ligand C2-BTBP show that the [Am(C2-BTBP)2]3+ complex is significantly more stable in aqueous solution than its Eu counterpart. The decisive factor stabilizing the Am3+ complexes over their Eu3+ analogues is the charge transfer from the ligands, somewhat greater on the 6d(AmIII) than on 5d(EuIII) orbitals. The covalency of M–N bonds in the [M(C2-BTBP)2]3+ complexes is greater than that of M–O bonds in [M(TEDGA)3]3+, but the latter is not negligible, in particular in the bonds with the oxygen atoms of the amide groups in TEDGA. The analysis of charge distribution over the whole molecules of the complexes shows that the TEDGA molecule is not hard as expected, but a relatively soft Lewis base, only slightly harder than BTBP. This conclusion has been confirmed by the calculation of the chemical hardness of the ligands. Moreover, the comparison of the results of bonding analysis with the calculated energies of complex formation in water and in the gas phase allows us to conclude that the population analysis, QTAIM topological parameters, and SOPT stabilization energy, as well as Wiberg and overlap-weighted NAO indices are the tools for analyzing the covalency rather than the total bond strength. [ABSTRACT FROM AUTHOR]

Using a fluorinated 1,1,1-trifluoro-2,4-pentanedione (Htfac) ligand and either 2,2'-bipyridine (bipy), bathophenanthroline (bath) or 5-nitro-1,10-phenanthroline (5NO2phen) as an ancillary ligand, three new ternary erbium(III) octacoordinated complexes have been synthesized. The single crystal structures of the new complexes (namely [Er(tfac)3(bipy)], [Er(tfac)3(bath)] and [Er(tfac)3(5NO2phen)]) have been determined and their properties have been investigated by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and thermodynamic analysis. After ligand-mediated excitation of these complexes in the UV, they all show the characteristic near-infrared (NIR) luminescence of the corresponding Er3+ ion at 1532 nm. The same emission in the C-band transmission window can also be obtained from the solutionprocessed organic light-emitting diodes (OLEDs) with structure: glass/ITO/PEDOT:PSS/[Er(tfac)3(N,Ndonor)]/ Ca/Al. In spite of the fact that the photoluminescence intensity of [Er(tfac)3(5NO2phen)] is stronger than those of [Er(tfac)3(bipy)] and [Er(tfac)3(bath)], the best electroluminescence results correspond to the OLED based on the [Er(tfac)3(bath)] complex, as a consequence of the superior electron transport capabilities of bathophenanthroline. [ABSTRACT FROM AUTHOR]

Three co-crystals of celecoxib (CEL) and bipyridine derivatives were synthesized based on the synthon design approach and structurally characterized. The resulting two-component complexes have different unit cell parameters and noticeably different packing patterns. Surprisingly, when different organic solvents are introduced into the binary-host crystal systems, six isostructural three-component crystals are obtained. These isomorphic complexes are formed by CEL with two different sets of bipyridine co-formers containing various solvent molecules. A robust H-bonding framework between CEL dimer molecules is found to tolerate subtle changes in the structures of the co-formers and guest solvent molecules. The physicochemical properties of these isomorphic co-crystals are fully examined and compared with their corresponding non-solvate forms. The desolvation mechanism and relative thermodynamic stabilities are also discussed. [ABSTRACT FROM AUTHOR]

In this work, the interactions between a viologen phosphorus dendrimer of generation 0 (VPD) and ATP or 2′-/3′-O-(N′-methylanthraniloyl)-ATP (Mant-ATP) were investigated by NMR and fluorescence spectroscopy methods. ATP and Mant-ATP were used as model molecules of purine and pyrimidine nucleoside analogues (NAs), which are antimetabolites commonly used in anticancer therapy. Complexes of VPD with NAs may help to overcome severe limitations of NAs associated with their low solubility, stability or resistance to cancer cells. The aim of the presented study was to evaluate the stoichiometry and the mechanism of formation of complexes between dendrimers and nucleotides: ATP and Mant-ATP. Moreover, we examined the efficiency of complex formation in relation to temperature, the type of solvent, NaCl concentration, pH and environment polarity. It was observed that viologen phosphorus dendrimers form complexes with ATP and Mant-ATP with high efficiency. Obtained complexes are stabilized by electrostatic and aromatic–aromatic interactions as driving forces. [ABSTRACT FROM AUTHOR]

A novel organic--inorganic hybrid monocapped/bicapped Keggin structure [CoII(bpy)3]6(H2bpy)[(CoIIbpy)2(PMo8VIMo4O40)]3 [(CoIIbpy)-(PMo8VIMo4V O40)]·16H2O (bpy = 2,2'-bipyridine) was synthesized and shown to be an efficient visible light-driven catalyst for water oxidation. [ABSTRACT FROM AUTHOR]

Five new [Pt(NN)(dtoc)] complexes (1-5; NN = diimine: 2,2'-bipyridine and its 4,4'-alkyl/aryl-substituted derivatives or 1,10-phenanthroline; dtoc2- = 1,2-dithiolate-1,2-closo-dicarbadodecaborane) have been synthesized and characterized by spectroscopic and electrochemical methods, and by means of X-ray diffraction in the case of complexes 1 and 4. Hybrid DFT and time-dependent (TD) DFT calculations were performed on complexes 1-5 and the previously reported complex [Pt(Ph2phen)(dtoc)] (6; Ph2phen = 4,7-diphenyl-1,10-phenanthroline) both in the gas phase and in the presence of several solvents (CH2Cl2, CHCl3, CH3CN, acetone, THF, DMF, DMSO, and toluene) to gain an insight into the electronic structure of the complexes and explain their experimental features. Theoretical calculations allowed for the determination of structure-property relationships within the series of the six complexes considered, and the prediction of their second order nonlinear optical (SONLO) properties by evaluating their first static hyperpolarizabilities (ßtot). [ABSTRACT FROM AUTHOR]

In this work, we report the discovery of a carboxyl-containing iron catalyst 1 (FeII-DCBPY, DCBPY = 2,2′-bipyridine-4,4′-dicarboxylic acid), which could activate the C–H bonds of cycloalkanes with high secondary (2°) C–H bond selectivity. A turnover number (TN) of 11.8 and a 30% yield (based on the H2O2 oxidant) were achieved during the catalytic oxidation of cyclohexane by 1 under irradiation with visible light. For the transformation of cycloalkanes and bicyclic decalins with both 2° and tertiary (3°) C–H bonds, 1 always preferred to oxidise the 2° C–H bonds to the corresponding ketone and alcohol products; the 2°/3° ratio ranged between 78/22 and ＞99/1 across 7 examples. 18O isotope labelling experiments, ESR experiments, a PPh3 method and the catalase method were used to characterize the reaction process during the oxidation. The success of 1 showed that, in addition to using a bulky catalyst, high 2° C–H bond selectivity could also be achieved using a less bulky molecular iron complex as the catalyst. [ABSTRACT FROM AUTHOR]

The synthesis, structures and magnetic characterisation of a family of discrete planar pentanuclear Cu(ii) 12-MC-4 metallacrowns of formulae [Cu5(L1)4(MeOH)4](ClO4)2 (1), [Cu5(L1)4(py)2](ClO4)2·py (2), [Cu5(L1)4(py)6](ClO4)2 (3) and [Cu5(L2)4(MeOH)4](ClO4)2·H2O (7) (where L1H2 = 2-(dimethylamino)phenylhydroxamic acid and L2H2 = 2-(amino)phenylhydroxamic acid) are reported. UV-vis and Electrospray MS studies indicate solution stability with respect to their {Cu5(L)4}2+ cores. Magnetic susceptibility measurements confirm strong antiferromagnetic exchange between the Cu(ii) ions resulting in isolated S = 1/2 ground spin states. The introduction of ditopic co-ligands such as 4,4′-bipyridine (4,4′-bipy), pyrazine (pz) and 4,4′-azopyridine (4,4′-azp) results in their coordination at a number of axial Cu(ii) sites within the {Cu5} metallacrown nodes to afford the extended networks {[Cu5(L1)4(4,4′-bipy)3](ClO4)2·(H2O)}n (4), {[Cu5(L1)4(4,4′-azp)2(MeOH)2](ClO4)2}n (5) and {[Cu5(L2)4(pz)2(MeOH)3](ClO4)2·MeOH}n (6). [ABSTRACT FROM AUTHOR]

Fulgimides monosubstituted with [M(bpy)3]2+ (M = Ru, Os; bpy = 2,2'-bipyridine) chromophore units and with a single bpy group were synthesized and investigated as components of conceivable dinuclear photochromic switches of luminescence. The E-, Z- and closed-ring (C) photoisomer forms of the bpy-bound fulgimide were successfully separated by semi-preparative HPLC. The same procedure failed, however, in the case of the [M(bpy)3]2+-substituted fulgimides. Energy transfer from the excited photochromic unit to the metal-bpy centre competes with the fulgimide cyclization, reducing the photocyclization quantum yields by approximately one order of magnitude compared to the non-complexed fulgimide-bpy ligand (φEC = 0.17, φEZ = 0.071, φZE = 0.15 at λexc = 334 nm). The cycloreversion of the fulgimide-bpy ligand is less efficient (φCE = 0.047 at λexc = 520 nm). The intensity of the ³MLCT-based luminescence of the metal-bpy chromophore (in MeCN, φdeaer = 6.6 × 10-2 and τdeaer = 1.09 μs for Ru; φdeaer = 6.7 × 10-3 and τdeaer = 62 ns for Os) is not affected by the fulgimide photoconversion. These results and supporting spectro-electrochemical data reveal that the lowest triplet excited states of the photochromic fulgimide moiety in all its E-, Z- and closed-ring forms lie above the lowest ³MLCT levels of the attached ruthenium and osmium chromophores. The actual components are therefore unlikely to form a triad acting as functional switch of energy transfer from [Ru(bpy)3]2+ to [Os(bpy)3]2+ through the photochromic fulgimide bridge. [ABSTRACT FROM AUTHOR]

Spontaneously precise organization of small structures into complex superstructures is ubiquitous and important in nature. But using small building blocks to mimic this process remains a challenge to scientists. Herein, we report the rational design of a bipyridine-derivative 1 and applied it for the self-assembly of nanorings. The addition of Fe2+ to the nanorings resulted in the assembly of the nanorings into supernanostructures via Fe2+–bipyridine coordination. HPLC, HR-ESI/MS, UV-vis, DLS, and TEM analyses clearly validated the intramolecular cyclization, self-assembly of the nanorings, and the additional self-assembly of the superstructures via Fe2+–bipyridine coordination. We envision our strategy to be a new approach of precisely assembling nanostructures of ring shape into more complex superstructures. [ABSTRACT FROM AUTHOR]

This work showed that the 4,4′-bipyridyl group and alkyl chains of 4,4′-bipyridyl derivatives are completely located in the shell-like cavity of the twisted cucurbit[14]uril molecule and formed novel shell-like 1 : 1 inclusion complexes. As it is enthalpy-driven the complexation benefits from ion–dipole interactions. [ABSTRACT FROM AUTHOR]

A significant improvement in the long-term stability for cobalt-based dye-sensitized solar cells (DSCs) under light-soaking conditions has been achieved by optimization of the composition of tris(2,2′-bipyridine) Co(ii)/Co(iii) electrolytes. The effects of component exchanges and changes were also studied during the optimization process. [ABSTRACT FROM AUTHOR]