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Transfer and inversion of supramolecular chirality from chiral calix[4]arene analogs (3D and 3L) with an alanine moiety to an achiral bipyridine derivative (1) with glycine moieties in a coassembled hydrogel are demonstrated. Molecular chirality of 3D and 3L could transfer supramolecular chirality to an achiral bipyridine derivative 1. Moreover, addition of 0.6 equiv of 3D or 3L to 1 induced supramolecular chirality inversion of 1. More interestingly, the 2D-sheet structure of the coassembled hydrogels formed with 0.2 equiv of 3D or 3L changed to a rolled-up tubular structure in the presence of 0.6 equiv of 3D or 3L. The chirality inversion and morphology change are mainly mediated by intermolecular hydrogen-bonding interactions between the achiral and chiral molecules, which might be induced by reorientations of the assembled molecules, confirmed by density functional theory calculations. [ABSTRACT FROM AUTHOR]

Complex Fe(bpyB)3 (1, bpyB = 5,5′-bis- (dimesitylboranyl)-2,2′-bipyridine) and its reduced species [(18-c-6)K(THF)2]·[Fe(bpyB)3] (2) were synthesized. Their solid state and electronic structures were investigated by single crystal X-ray crystallography, electron paramagnetic resonance and UV-vis spectroscopy, and SQUID measurements. In 1 two bpyB radical anions are fused by a diamagnetic FeII ion, whereas in 2 all three bpyB ligands are in the radical state. Complex 1 possesses an open-shell singlet ground state with a singlet-triplet gap of 0.18 kcal mol-1 and 2 features an open-shell doublet ground state with a doublet-quartet gap of 1.4 kcal mol-1, as determined by SQUID measurements. The unpairedelectrons in 1 and 2 mainly delocalize over the boron atoms and the bipyrdine moieties with negligible spin density at the iron center. Complex 2 represents the first isolable example of boron-based triradicals. [ABSTRACT FROM AUTHOR]

Herein we report the coordination chemistry and structural properties of two multifunctional terdentate 2,2'-bipyridine derivatives 4- and 3-(4-nitrophenyl)-2,2'-bipyridine-6-carboxylate, L1/L2, respectively. We report eight new coordination complexes with CdII, CoII, and CoIII, and study their behavior in the crystalline phase with the view of establishing L1 and L2 as robust and functional chelators for use in extended metallosupramolecular systems. The divalent complexes [Cd(L1)2]·H2O 1, [Cd(L2)2] 2, [Co(L1)2] 5, and [Co(L2)2] 7 are mononuclear complexes with distorted octahedral coordination geometries dictated by the two meridionally coordinated L1/L2 ligands. Also reported are two trivalent byproducts [Co(L1)2]NO36 and [Co(L2)2]NO38 which were formed in trace quantities during the initial screening of complexes 5 and 7, respectively. The extended structures of these complexes are dominated by substantial intermolecular interactions, including anion···π hole interactions. Modification of the reaction conditions from 1 and 2 gives two closely related trinuclear cluster species [Cd3(L1)3(NO3)2(DMF)4]NO33 and [Cd3(L2)3(NO3)2(DMF)4]NO3·DMF 4, in which three cadmium ions, with pentagonal bipyramidal coordination geometries, form disc-shaped assemblies with L1/L2, which undergo further weak interactions between neighboring complexes in the crystalline state. With these outcomes L1 and L2 are established as exciting new building blocks for metallosupramolecular assemblies involving d-block metal ions. [ABSTRACT FROM AUTHOR]

A novel type of energy donor-acceptor system on a clay surface has been prepared. The energy transfer between an energy-donating cationic pyrene derivative (An-Py2+) and an energy-accepting tris(bipyridine)ruthenium complex (Ru2+) on the clay surface was investigated using absorption, emission, and lifetime measurements. An obvious energy transfer was observed, and one Ru2+ molecule quenched the emission from five molecules of An-Py2+ with an emission quenching efficiency of 85% on the clay surface. This suggests that the light energies absorbed by five of the An-Py2+ molecules were accumulated in the one Ru2+ molecule. Near-quantitative emission quenching was observed for stoichiometric amounts of An-Py2+ and Ru2+. The apparent quenching rate constant is approximately 1017 L mol-1 s-1, and thus the quenching rate constant is 107-108 times higher than the diffusion rate constant in a homogeneous solution. [ABSTRACT FROM AUTHOR]

A majority of the reported electrografting of aryldiazonium salts result in the formation of covalently attached films with a limited surface coverage of below 5 nmol ⋅ cm-2. Herein, we report the preparation of higher-thickness redox-active viologen-grafted electrodes from the electroreduction of viologen phenyl diazonium salts, by either cyclic voltammetric (CV) sweeps or electrolysis using a fixed potential. Both of the methodologies were successfully applied for various conductive surfaces, including glassy carbon (GC), gold disc, indium tin oxide glass, mesoporous TiO2 electrodes, and 3D compacted carbon fibers. A robust maximal viologen coverage, Γviologen = 9.5 nmol·cm-2, was achieved on a GC electrode by CV electroreduction. Electroreduction held at a fixed potential at Eappl. = -0.3 V can fabricate viologen-grafted electrodes with Γviologen in the range of 0-37 nmol·cm-2 in a controllable way, by simply adjusting the electrodeposition time tappl.. Time-dependent Γviologen were found to be 10 nmol·cm-2@2 min, 20 nmol·cm-2@4.2 min, and 30 nmol·cm-2@7 min. Furthermore, a TiO2 electrode coupled with Γviologen of 140 nmol·cm-2 exhibited electrochromic performance, with the color changing from pale yellow to blue and red brown. [ABSTRACT FROM AUTHOR]

Reduction of (η5-C5Me5)2ThCl2 (1) with potassium graphite (KC8) in the presence of 2,2'-bipyridine forms the thorium bipy metallocene (η5-C5Me5)2Th(bipy) (2) in good yield. Complex 2 was fully characterized and reacts with various small molecules. For example, 2 serves as a source for the (η5-C5Me5)2Th(II) fragment when exposed to conjugated alkynes, elemental sulfur and their organic derivatives, diazabutadiene, carbodiimide, CS2, isothiocyanate, and organic azides. Furthermore, treatment of 2 with ketone Ph2CO, thio-ketone Ph2CS, imine PhCH=NPh, and nitrile PhCN results in C-C bond coupling products (η5-C5Me5)2Th[(bipy)(Ph2CO)] (10), (η5-C5Me5)2Th[(bipy)(Ph2CS)] (11), (η5-C5Me5)2Th[(bipy)(PhCHNPh)] (12), and (η5-C5Me5)2Th[(bipy)(PhCN)] (13), respectively, in quantitative conversion. [ABSTRACT FROM AUTHOR]

This article demonstrates a series of cyclometalated Ir(III) complexes of the type [IrIII(CN)2(NN)](PF6), where CN is 2-phenylpyridine, and NN corresponds to the 4,4′-π-conjugated 2,2′-bipyridine ancillary ligands. All these compounds were synthesized through splitting of the binuclear dichloro-bridged complex precursor, [Ir(CN)2(μ-Cl)]2, with the appropriate bipyridine ligands followed by the anion exchange reaction. The linear and nonlinear absorption properties of the synthesized complexes were investigated. The absorption spectra of all the title complexes exhibit a broad structureless feature in the spectral region of 350-700 nm with two bands being well-resolved in most of the cases. The structures of all the compounds were modeled in dichloromethane using the density functional theory (DFT) algorithm. The nature of electronic transitions was further comprehended on the basis of time-dependent DFT analysis, which indicates that the origins of various bands are primarily due to intraligand charge transfer transitions along with mixed-metal and ligand-centered transitions. The synthesized compounds are found to be nonemissive at room temperature because of probable nonradiative deactivation pathways of the T1 state that compete with the radiative (phosphorescence) decay modes. However, the frozen solutions of compounds Ir(MS 3) and Ir(MS 5) phosphoresce at the near-IR region, the other complexes remaining nonemissive up to 800 nm wavelength window. The two-photon absorption studies on the synthesized complexes reveal that values of the absorption cross-section are quite notable and lie in the range of 300-1000 GM in the picosecond case and 45-186 GM in the femtosecond case. [ABSTRACT FROM AUTHOR]

The most relevant manifestations of ligand noninnocence of quinone and bipyridine derivatives are thoroughly scrutinized and discussed through an extensive and systematic set of octahedral ruthenium complexes, [(en)2RuL]z, in four oxidation states (z = +3, +2, +1, and 0). The characteristic structural deformation of ligands upon coordination/noninnocence is put into context with the underlying electronic structure of the complexes and its change upon reduction. In addition, by means of decomposing the corresponding reductions into electron transfer and structural relaxation subprocesses, the energetic contribution of these structural deformations to the redox energetics is revealed. The change of molecular electron density upon metal- and ligand-centered reductions is also visualized and shown to provide novel insights into the corresponding redox processes. Moreover, the charge distribution of the p-subspace is straightforwardly examined and used as indicator of ligand noninnocence in the distinct oxidation states of the complexes. The aromatization/dearomatization processes of ligand backbones are also monitored using magnetic (NICS) and electronic (PDI) indicators of aromaticity, and the consequences to noninnocent behavior are discussed. Finally, the recently developed effective oxidation state (EOS) analysis is utilized, on the one hand, to test its applicability for complexes containing noninnocent ligands, and, on the other hand, to provide new insights into the magnitude of state mixings in the investigated complexes. The effect of ligand substitution, nature of donor atom, ligand frame modification on these manifestations, and measures is discussed in an intuitive and pedagogical manner. [ABSTRACT FROM AUTHOR]

Three binuclear and one mononuclear cobalt(III) dioximates with the compositions [Co2(dmgH)4(bpy)Cl2]·1.5dmf (1), [Co2(nioxH)4(bpy)Cl2]·0.5H2O (2), [Co2(dmgH)4(bpe)Cl2]·0.5H2O (3), and [Co(dmgH)2(bpy)Cl]·H2O (4) (where dmgH2 = dimethylglyoxime, nioxH2 = 1,2-cyclohexanedionedioxime, bpy = 4,4'-bipyridine, bpe = 1,2-bis(4-pyridyl)ethane, and dmf = N,N-dimethylformamide) were prepared by replacement of water molecule in Co(III) mononuclear dioximates by bpy and bpe ligands. All compounds were characterized by single-crystal X-ray diffraction and spectroscopic techniques. In all complexes Co(III) atoms have an identical octahedral N5Cl environment formulated by four nitrogen atoms of two mono-deprotonated oxime ligands in a square planar mode, and the nitrogen atom of the bpy/bpe molecules and chloride atom in the axial positions. In 1-3 bpy/bpe exobidentate spacer ligands serve as bridging "rods" and unite two planar cobalt(III) bis-dioximates in binuclear complex with wheel-and-axle topology. The packing of bulky binuclear complexes results in formation of porous structure with hourglass-like channels of diameter ca. 0.6-1.3 nm in the crystal of compound 1 and smaller cavities in 2. The sorption properties for 1 were also measured. The π···π stacking interaction between monodentate bpy ligands of mononuclear complexes 4 emulate supramolecular binuclear assembly with wheel-and-axle topology. [ABSTRACT FROM AUTHOR]

A new series of monosubstituted styryl- and bistyryl-2,2'-bipyridine luminophores (compounds 16-23) have been synthesized via Horner-Wadsworth-Emmons reaction involving a monophosphonate and donor aromatic aldehydes. In the title chromophores, the amino donors are varied between acyclic and cyclic while the alkoxy donors are varied in terms of their number and position. The absorption maxima of these chromophores shift predominantly due to intramolecular charge transfer (ICT) between different donor and acceptor moieties. The title donor-acceptor molecules exhibit intense fluorescence in solution at room temperature, and their emissive behavior has been found to be highly sensitive to solvent polarity. The fluorescence spectra and quantum yields of all the chromophores were recorded in four different solvent media, and the chromophores 16, 17, 19, and 21 exhibit fluorescence in the solid state too. The influence of the nature and position of the donor functionalities in the conjugated backbone of the bipyridine moiety on the electronic absorption properties of the title chromophores (16-23) has been demonstrated, which has further been corroborated by DFT and TD-DFT computation both in gas phase and in solution phase. The crystal structure of compound 18 has been described as a representative member of the family (16-23). [ABSTRACT FROM AUTHOR]

We report a structure-property study on phosphoryl-bridged viologen analogues with a remarkably low reduction threshold. Utilizing different benzyl groups for N-quaternization, we were able to confirm the p-benzyl substituent effect on the electronic tunability of the system while maintaining the characteristic chromic response of viologens with two fully reversible one-electron reductions. Due to the considerably increased electron-acceptor properties of the phosphoryl-bridged bipyndine precursor, N-benzylation was found to be very challenging and required the development of new synthetic strategies toward the target viologen species. This study also introduces a new and convenient way for the anion exchange of viologen systems by utilizing methyl triflate. Finally, the practical utility of the new species was verified in simplified proof-of-concept electrochromic devices. [ABSTRACT FROM AUTHOR]

The synthesis, stability, and photophysical properties of [2 + 1] Re(I)/Tc(I) complexes derived from bipyridine and a series of imidazole derivatives were investigated as a means of identifying complexes suitable for creating targeted isostructural optical/nuclear molecular imaging probes. To prepare the desired complexes, [Re(CO)3(H2O)3]Br was combined with 2,2'-bipyridine (bipy) to give [Re(CO)3(bipy)Br], which in turn was converted to the desired complexes by treatment with functionalized imidazoles, yielding crystal structures of two new Re complexes. The corresponding 99mTc complexes [99mTc(CO)3(bipy)(L)]+ (L = imidazole derivatives) were prepared by combining [99mTc(CO)3(bipy)(H2O)]Cl with the same series of ligands and heating at 40 or 60 °C for 30 min. Quantitative transformation to the final products was confirmed in all cases by HPLC, and the nature of the complexes was verified by comparison to the authentic Re standards. Incubation in saline and plasma, and amino acid challenge experiments showed that N-substituted imidazole derivatives, bearing electron donating groups, exhibited superior stability to analogous metal complexes derived from less basic ligands. Imaging studies in mice revealed that with the appropriate choice of monodentate ligand, it is possible to prepare robust [2 + 1] Tc complexes that can be used as the basis for preparing targeted isostructural optical and nuclear probes. [ABSTRACT FROM AUTHOR]

The synthesis of Mn-based catalysts to mimic the structural and catalytic properties of the oxygen-evolving complex in photosystem II is a long-standing goal for researchers. An interesting result in this field came with the synthesis of a Mn complex that enables water oxidation driven by the mild single-electron oxidant [Ru(bpy)3]3+. On the basis of hybrid density functional calculations, we herein propose a water oxidation mechanism for this bioinspired Mn catalyst, where the crucial O-O bond formation proceeds from the formal Mn4IV,IV,IV,V state by direct coupling of a MnIV-bound terminal oxyl radical and a di-Mn bridging oxo group, a mechanism quite similar to the presently leading suggestion for the natural system. Of importance here is that the designed ligand is shown to be redox-active and can therefore store redox equivalents during the catalytic transitions, thereby alleviating the redox processes at the Mn centers. [ABSTRACT FROM AUTHOR]

A new triad system featuring one zinc porphyrin and one fullerene moieties attached to a central redox-active Re(I) connector was obtained in remarkable yield by cleverly exploiting a facile two-step synthesis. Detailed description and discussion on the characterization of this multicomponent system and of its parent free-base analogue are presented, along with a kinetic study of the stepwise electron-transfer processes occurring upon visible excitation. [ABSTRACT FROM AUTHOR]

A series of chiral cyclometalated platinum(II) complexes, [Pt((-)-L1)(Dmpi)]Cl ((-)-1), [Pt((+)-L1)(Dmpi)]Cl ((+)-1), [Pt((-)-L2)(Dmpi)]Cl ((-)-2), [Pt((+)-L2)(Dmpi)]Cl ((+)-2), [Pt3((-)-L2)2(Dmpi)4](ClO4)4 ((-)-3), and [Pt3((+)-L2)2(Dmpi)4](ClO4)4 ((+)-3) [(-)-L1 = (-)-4,5-pinene-6'-phenyl-2,2'-bipyridine, (+)-L1 = (+)-4,5-pinene-6'-phenyl-2,2'-bipyridine), (-)-L2 = (-)-1,3-bis(2-(4,5-pinene)pyridyl)benzene, (+)-L2 = (+)-1,3-bis(2-(4,5-pinene)pyridyl)benzene, Dmpi = 2,6-dimethylphenyl isocyanide], have been designed and synthesized. In aqueous solutions, (-)-1 and (+)-1 aggregate into one-dimensional helical chain structures through Pt···Pt, π-π, and hydrophobic-hydrophobic interactions. (-)-3 and (+)-3 represent a novel helical structure with Pt-Pt bonds. The formation of helical structures results in enhanced and distinct chiroptical properties as evidenced by circular dichroism spectra. Circularly polarized luminescence (CPL) was observed from the aggregates of (-)-1 and (+)-1 in water, as well as (-)-3 and (+)-3 in dichloromethane. The CPL activity can be switched reversibly (for (-)-1 and (+)-1) or irreversibly (for (-)-3 and (+)-3) by varying the temperature. [ABSTRACT FROM AUTHOR]

A tris (bipyridine) ligand 1 with two BINOL (BINOL = 2,2'-dihydroxy-l,T-binaphthyl) groups has been prepared in two enantiomerically pure forms. This ligand undergoes completely diastereoselective self-assembly into D2- symmeteric double-stranded trinuclear helicates upon coordination to copper(l) and silver(l) ions and to D3-symmetric triple-stranded trinuclear helicates upon coordination to copper(ll), zinc(II), and iron(II) ions as demonstrated by mass spectrometry, NMR and CD spectroscopy in combination with quantum chemical calculations and X-ray diffraction analysis. According to the calculations, the single diastereomers that are formed during the self-assembly process are strongly preferred compared to the next stable diastereomers. Due to this strong preference, the self-assembly of the helicates from racemic 1 proceeds in a completely narcissistic self-sorting manner with an extraordinary high degree of self-sorting that proves the power and reliability of this approach to achieve high-fidelity diastereoselective self-assembly via chiral self-sorting to get access to stereochemically well-defined nanoscaled objects. Furthermore, mass spectrometric methods including electron capture dissociation MS" experiments could be used to elucidate the redox behavior of the copper helicates. [ABSTRACT FROM AUTHOR]

Air-stable doping of transition metal dichalcogenides is of fundamental importance to enable a viride range of optoelectronic and electronic devices while exploring their basic material properties. Here we demonstrate the use of benzyl viologen (BV), which has one of the highest reduction potentials of all electrondonor organic compounds, as a surface charge transfer donor for MoS2 flakes. The n-doped samples exhibit excellent stability in both ambient air and vacuum. Notably, we obtained a high electron sheet density of ∼1.2 × 1013 cm-2, which corresponds to the degenerate doping limit for MoS2. The BV dopant molecules can be reversibly removed by immersion in toluene, providing the ability to control the carrier sheet density as well as selective removal of surface dopants on demand. By BV doping of MoS2 at the metal junctions, the contact resistances are shown to be reduced by a factor of >3. As a proof of concept, top-gated field-effect transistors were fabricated with BV-doped n+ source/drain contacts selfaligned with respect to the top gate. The device architecture, resembling that of the conventional Si transistors, exhibited excellent switching characteristics with a subthreshold swing of ~77 mV/decade. [ABSTRACT FROM AUTHOR]

The selective C–H bond activationof N-isopropyl-N-phenyl-2,2′-bipyridin-6-aminepromoted by Pt(II)was complicated by the low selectivity of sp2C–Hbond activation in acetonitrile and low yield of sp3C–Hactivation in acetic acid. The use of a base was found to effectivelysuppress the competing sp3C–H bond activation inacetonitrile, improving the selectivity of sp2C–Hbond activation from 70% to 99%. In the reaction in acetic acid, thelow yield was due to the competing C–N bond cleavage. The useof a base reduced the C–N bond cleavage, but not completely.The reaction of N-tert-butyl-N-phenyl-2,2′-bipyridin-6-amine with K2PtCl4in acetic acid produced the cyclometalated complexwith complete C–N bond cleavage and its acylated derivative.These results indicated that the C–N bond cleavage might proceedvia heterolytic C–N bond dissociation. The acylation followingthe C–N cleavage in the reaction in acetic acid is regioselective.Further experiments showed that the reaction of N-phenyl-2,2′-bipyridin-6-amine with K2PtCl4in acetic acid produced the cyclometalated complex, whilethe reaction in a mixture of acetic anhydride and acetic acid producedthe acylated cyclometalated complex. An X-ray crystal structure studyrevealed strong intramolecular H bonding in the acylated complexes.The regioselectivity was explained in terms of H bonding and the electrondistribution predicted by the DFT calculations. [ABSTRACT FROM AUTHOR]

The ability to confine photoactive catalysts within metal–organicframework (MOF) materials affords the opportunity to expand the functionaldiversity of these materials into solar based applications. Here,the confinement of Ru(II)tris(2,2′-bipyridine) (RuBpy) by aMOF material derived from Zn(II) ions and trimesic acid (hereafter,USF2) is examined. Although the encapsulated RuBpy could not be crystallographicallyresolved within the MOF framework, the photophysical properties ofthe complex are characteristic of confinement including extended tripletmetal-to-ligand (3MLCT) lifetime (τethanol= 614 ns and τUSF2= 1.2 μs at 25 °C)and a slight hypsochromic shift in the steady-state emission spectrumrelative to RuBpy in ethanol. The extended lifetime is attributedto a deactivation of a nonradiative 3dd that is antibondingwith respect to the Ru(II)-bipyridine due to a confined molecularenvironment. These results represent one of the first examples ofRuBpy encapsulation and photophysical characterization within a polyhedralMOF material. [ABSTRACT FROM AUTHOR]

A novel class of luminescent gold(III) complexes containing various tridentate cyclometalaring ligands derived from 6-phenyl-2,2'-bipyridine and alkynyl ligands, [Au- (RC∧N∧N)(C≡C-R')]PF6, has been successfully synthesized and characterized. One of the complexes has also been determined by X-ray crystallography. Electrochemical studies show a ligand-centered reduction originated from the cyclometalaring RC∧N∧N ligands as well as an alkynyl-centered oxidation. The electronic absorption and photoluminescence properties of the complexes have also been investigated. In acetonitrile at room temperature, the complexes show intense absorption at higher energy region with wavelength shorter than 320 nm, and a moderately intense broad absorption band at 374-- 406 nm, assigned as the metal-perturbed intraligand π--π* transition of the cyclometalating RC∧N∧N ligand, with some charge transfer character from the aryl ring to the bipyridine moiety. Most of the complexes have been observed to show vibronicstructured emission bands at 469--550 nm in butyronitile glass at 77 K, assigned to an intraligand excited state of the RC∧N∧N ligand, with some charge transfer character from the aryl to the bipyridyine moiety. Insights into the origin of the absorption and emission have also been provided by density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. [ABSTRACT FROM AUTHOR]

Caerulomycins (CAEs) and collismycins (COLs), which mainly differ in sulfur decoration, are two groups of structurally similar natural products containing a 2,2'-bipyridine (2,2-BP) core, derivatives of which have been widely used in chemistry. The biosynthetic pathways of CAEs and COLs remain elusive. In this work, cloning of the CAE biosynthetic gene cluster allowed us to mine a highly conserved gene cluster encoding COL biosynthesis in a Streptomyces strain that was previously unknown as a 2,2'-BP producer. In vitro and in vivo investigations into the biosynthesis revealed that CAEs and COLs share a common paradigm featuring an atypical hybrid polyketide synthase/nonribosomal peptide synthetase system that programs the 2,2'-BP formation. This likely involves an unusual intramolecular cyclization/rearrangement sequence, and a difference in processing of the sulfhydryl group derived from the same precursor cysteine drives the biosynthetic route toward CAEs or COLs. [ABSTRACT FROM AUTHOR]

A new generation of a flexible bipyridine-based ligand, 1,4-bis(4-pyridyl)-piperazine, with two main stable states (chair and twist-boat forms) was employed in the construction of unusual dirhenium metallacycles. A new generation of a flexible bipyridine-based ligand, 1,4-bis(4-pyridyl)piperazine, with two main stable states (chair and twist-boat forms) was employed in the construction of unusual metallacycles. The successful assembly of dirhenium metallacycles proves the applicability of the concept of self-adaptation and switching of the title building unit. [ABSTRACT FROM AUTHOR]