Polar Nature of (CH3NH3)3Bi2I9 Perovskite-Like Hybrids.

High-quality single crystals of perovskite-like (CH3NH3)3Bi2I9 hybrids have been synthesized, using a layered-solution crystal-growth technique. The large dielectric constant is strongly affected by the polar ordering of its constituents. Progressive dipolar ordering of the methylammonium cation upon cooling below 300 K gradually converts the hexagonal structure (space group P63/mmc) into a monoclinic phase (C2/c) at 160 K. A well-pronounced, ferrielectric phase transition at 143 K is governed by in-plane ordering of the bismuth lone pair that breaks inversion symmetry and results in a polar phase (space group P21). The dielectric constant is markedly higher in the C2/c phase above this transition. Here, the bismuth lone pair is disordered in-plane, allowing the polarizability to be substantially enhanced. Density functional theory calculations estimate a large ferroelectric polarization of 7.94 µC/cm2 along the polar axis in the P21 phase. The calculated polarization has almost equal contributions of the methylammonium and Bi3+ lone pair, which are fairly decoupled.

Towards Redox-Driven Unidirectional Molecular Motion.

Redox-driven molecular motion is an attractive alternative to light-driven processes. Here, the ability of an overcrowded alkene-based unimolecular light-driven rotary motor (A) to be driven by oxidation/reduction cycles is explored. We show that two-electron oxidation of A is followed by irreversible deprotonation and reduction to form a monocationic species D(+) , in which the stereogenic center is lost. This latter species was isolated through preparative electrolysis and its structure was confirmed by using single-crystal X-ray analysis. However, at short timescales and in the absence of Brønsted acids, these processes can be outrun and the oxidation of A to a dicationic species B(2+) occurs, in which the central double bond (the axle of the molecular motor) becomes a single bond; when followed by rapid reduction, it results in the reformation of A, potentially in both its stable and unstable conformations. The latter conformation, if formed, undergoes thermal helix inversion, completing a rotary cycle. The data obtained regarding these reactions provide a window of opportunity for the motor to be driven electrochemically, without degradation from chemical reactions of the oxidized motor.

Binding of copper(II) polypyridyl complexes to DNA and consequences for DNA-based asymmetric catalysis.

The interaction between salmon testes DNA (st-DNA) and a series of Cu(II) polypyridyl complexes, i.e. [Cu(dmbpy)(NO3)2] (1) (dmbpy = 4,4'-dimethyl-2,2'-bipyridine), [Cu(bpy)(NO3)2] (2) (bpy = 2,2'-bipyridine), [Cu(phen)(NO3)2] (3) (phen = phenanthroline), [Cu(terpy)(NO3)2]·H2O (4) (terpy = 2,2':6',2″-terpyridine), [Cu(dpq)(NO3)2] (5) (dpq = dipyrido-[3,2-d:2',3'-f]-quinoxaline) and [Cu(dppz)(NO3)2] (6) (dppz = dipyrido[3,2-a:2',3'-c]phenazine) was studied by UV/Vis absorption, Circular Dichroism, Linear Dichroism, EPR, Raman and (UV and vis) resonance Raman spectroscopies and viscometry. These complexes catalyse enantioselective C-C bond forming reactions in water with DNA as the source of chirality. Complex 1 crystallizes as an inorganic polymer with nitrate ligands bridging the copper ions, which adopt essentially a distorted square pyramidal structure with a fifth bridging nitrate ligand at the axial position. Raman spectroscopy indicates that in solution the nitrate ligands in 1, 2, 3 and 4 are displaced by solvent (H2O). For complex 1, multiple supramolecular species are observed in the presence of st-DNA in contrast to the other complexes, which appear to interact relatively uniformly as a single species predominantly, when st-DNA is present. Overall the data suggest that complexes 1 and 2 engage primarily through groove binding with st-DNA while 5 and 6 undergo intercalation. For complexes 3 and 4 the data indicates that both groove binding and intercalation takes place, albeit primarily intercalation. Although it is tempting to conclude that the groove binders give highest ee and rate acceleration, it is proposed that the flexibility and dynamics in binding of Cu(II) complexes to DNA are key parameters that determine the outcome of the reaction. These findings provide insight into the complex supramolecular structure of these DNA-based catalysts.

Nickel(II) in chelate N2O2 environment. DFT approach and in-depth molecular orbital and configurational analysis.

The O-N-N-O-type tetradentate ligands H2S,S-eddp (H2S,S-eddp stands for S,S-ethylenediamine-N,N'-di-2-propionic acid) and H2edap (H2edap stands for ethylenediamine-N-acetic-N'-3-propionic acid) and the corresponding novel octahedral nickel(II) complexes have been prepared and characterized. N2O2 ligands coordinate to the nickel(II) ion via four donor atoms (two deprotonated carboxylate atoms and two amine nitrogens) affording octahedral geometry in the case of all investigated Ni(II) complexes. A six coordinate, octahedral geometry has been verified crystallographically for the s-cis-[Ni(S,S-eddp)(H2O)2] complex. Structural data correlating similarly chelated Ni(II) complexes have been used to carry out an extensive configuration analysis. Molecular mechanics and Density Functional Theory (DFT) have been used to model the most stable geometric isomer, yielding, at the same time, significant structural and spectroscopic (TDDFT) data. The results from density functional studies have been compared to X-ray data. Natural Bond Orbital (NBO) and Natural Energetic Decomposition Analysis (NEDA) have been done for the [Ni(edda-type)(H2O)(2-n)] and nH2O fragments. Molecular orbital analysis (MPA) is given as well. The infra-red and electronic absorption spectra of the complexes are discussed in comparison to the related complexes of known geometries.

6-[(2,4-Di-methyl-anilino)methyl-idene]-2-hy-droxy-cyclo-hexa-2,4-dienone.

In the title compound, C15H15NO2, the dihedral angle between the aromatic rings is 5.86 (6)°, and an intra-molecular N-H⋯O hydrogen bond generates an S(6) motif, which helps to stabilize the enamine-keto tautomer. An intra-molecular O-H⋯O hydrogen bond also occurs. In the crystal, inversion dimers linked by pairs of O-H⋯O hydrogen bonds generate R 2 (2)(10) loops. A C-H⋯O inter-action links the dimers into [010] chains and aromatic π-π stacking [centroid-centroid separation = 3.6131 (9) Å] also occurs.

Antitumor effects of a tetradentate amido-carboxylate ligands and corresponding square-planar palladium(II) complexes toward some cancer cells. Crystal structure, DFT modeling and ligand to DNA probe docking simulation.

Novel square-planar palladium(II) complexes with O-N-N-O-type ligands H4mda (H4mda=malamido-N,N'-diacetic acid) and H4obp (H4obp=oxamido-N,N'-di-3-propionic acid) were prepared and characterized. The ligands coordinate to the palladium(II) ion via two pairs of deprotonated ligating atoms with square chelation. A four coordinate, square-planar geometry was verified crystallographicaly for the K2[Pd(mda)]·H2O complex. The binary and ternary systems of Pd(II) ion with H4mda or H4obp (L) as primary ligands and guanosine (A) as secondary ligand were studied in aqueous solutions in 0.1 M NaCl ionic medium at 25 °C by potentiometric titrations. In addition, calculations based on density functional methods (DFT) were carried out. A natural bonding orbital analysis indicated that the Pd-N bonds are three-centric in nature and mainly governed by charge transfer via a strong delocalization of the oxygen lone pair with "p" character into the bonding Pd-N orbital. Mononuclear palladium(II) complexes together with amido acid N,O-containing ligands were tested against several tumor cells and reveal significant antitumor activity and lower resistance of tumor cells in vitro than cisplatin. In this paper, interactions of palladium complexes with DNA are discussed in order to provide guidance and determine structure and antitumor activity relationships for continuing studies of these systems. Docking simulation on DNA dodecamer or 29-mer (Lippard solved crystal structures), suggests several favorable interactions with the hydrogen pocket/binding site for the incoming ligands. These results support amidoacids/Pd complexes as novel antitumor drugs and suggest that their potent cell life inhibition may contribute to its anti-cancer efficacy.

Synthetic, crystallographic, and computational study of copper(II) complexes of ethylenediaminetetracarboxylate ligands.

Copper(II) complexes of hexadentate ethylenediaminetetracarboxylic acid type ligands H(4)eda3p and H(4)eddadp (H(4)eda3p = ethylenediamine-N-acetic-N,N',N'-tri-3-propionic acid; H(4)eddadp = ethylenediamine-N,N'-diacetic-N,N'-di-3-propionic acid) have been prepared. An octahedral trans(O(6)) geometry (two propionate ligands coordinated in axial positions) has been established crystallographically for the Ba[Cu(eda3p)]·8H(2)O compound, while Ba[Cu(eddadp)]·8H(2)O is proposed to adopt a trans(O(5)) geometry (two axial acetates) on the basis of density functional theory calculations and comparisons of IR and UV-vis spectral data. Experimental and computed structural data correlating similar copper(II) chelate complexes have been used to better understand the isomerism and departure from regular octahedral geometry within the series. The in-plane O-Cu-N chelate angles show the smallest deviation from the ideal octahedral value of 90°, and hence the lowest strain, for the eddadp complex with two equatorial ß-propionate rings. A linear dependence between tetragonality and the number of five-membered rings has been established. A natural bonding orbital analysis of the series of complexes is also presented.

Ligand exchange and spin state equilibria of Fe(II)(N4Py) and related complexes in aqueous media.

We report the characterization and solution chemistry of a series of Fe(II) complexes based on the pentadentate ligands N4Py (1,1-di(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine), MeN4Py (1,1-di(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)ethanamine), and the tetradentate ligand Bn-N3Py (N-benzyl-1,1-di(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine) ligands, i.e., [Fe(N4Py)(CH(3)CN)](ClO(4))(2) (1), [Fe(MeN4Py)(CH(3)CN)](ClO(4))(2) (2), and [Fe(Bn-N3Py)(CH(3)CN)(2)](ClO(4))(2) (3), respectively. Complexes 2 and 3 are characterized by X-ray crystallography, which indicates that they are low-spin Fe(II) complexes in the solid state. The solution properties of 1-3 are investigated using (1)H NMR, UV/vis absorption, and resonance Raman spectroscopies, cyclic voltammetry, and ESI-MS. These data confirm that in acetonitrile the complexes retain their solid-state structure, but in water immediate ligand exchange of the CH(3)CN ligand(s) for hydroxide or aqua ligands occurs with full dissociation of the polypyridyl ligand at low (<3) and high (>9) pH. pH jumping experiments confirm that over at least several minutes the ligand dissociation observed is fully reversible for complexes 1 and 2. In the pH range between 5 and 8, complexes 1 and 2 show an equilibrium between two different species. Furthermore, the aquated complexes show a spin equilibrium between low- and high-spin states with the equilibrium favoring the high-spin state for 1 but favoring the low-spin state for 2. Complex 3 forms only one species over the pH range 4-8, outside of which ligand dissociation occurs. The speciation analysis and the observation of an equilibrium between spin states in aqueous solution is proposed to be the origin of the effectiveness of complex 1 in cleaving DNA in water with (3)O(2) as terminal oxidant.

Spectroscopic and magnetic properties of a series of µ-cyano bridged bimetallic compounds of the type M(II)-NC-Fe(III) (M = Mn, Co, and Zn) using the building block [Fe(III)(CN)5imidazole]2-.

In this contribution, we describe the preparation and single-crystal X-ray diffraction of a new building block for bimetallic solid state materials. X-ray diffraction data of these complexes indicate that (PPh(4))(2)[Fe(CN)(5)imidazole]·2H(2)O crystallizes in the triclinic space group P1 with a = 9.8108(15) Å, b = 11.1655(17) Å, c = 23.848(4) Å, α = 87.219(2)°, ß = 85.573(2)°, γ = 70.729(2)°, and Z = 2, while its precursor Na(3)[Fe(CN)(5)(en)]·5H(2)O crystallizes in the monoclinic space group P2(1)/n with a = 8.3607(7) Å, b = 11.1624(9) Å, c = 17.4233(14) Å, ß = 90.1293(9)°, and Z = 4. Spectroscopic and magnetic properties of a series of bimetallic materials were obtained by reaction of the complex [Fe(CN)(5)imidazole](2-) with hydrated transition metal ions [M(H(2)O)(n)](2+) (M = Mn, Co, Zn; n = 4 or 6). The new bimetallic materials obtained are [Co(H(2)O)(2)][Fe(CN)(5)imidazole]·2H(2)O (1), [Mn(CH(3)OH)(2)][Fe(CN)(5)imidazole] (2), Zn[Fe(CN)(5)imidazole]·H(2)O (3), and [Mn(bpy)][Fe(CN)(5)imidazole].H(2)O (4). All of the complexes crystallize in the orthorhombic system. X-ray single-crystal analysis of the compounds identified the Imma space group with a = 7.3558(10) Å, b = 14.627(2) Å, c = 14.909(2) Å, and Z = 4 for 1; the P2(1)2(1)2(1) space group with a = 7.385(5) Å, b = 13.767(9) Å, c = 14.895(10) Å, and Z = 4 for 2; the Pnma space group with a = 13.783(2) Å, b = 7.167(11) Å, c = 12.599(2) Å, and Z = 4 for 3; and the Pnma space group with a = 13.192(3) Å, b = 7.224(16) Å, c = 22.294(5) Å, and Z = 4 for 4. The structures of 1, 2, and 4 consist of two-dimensional network layers containing, as the repeating unit, a cyclic tetramer [M(2)Fe(2)(CN)(4)] (M = Mn, Co). H bonding between the layers in the structure of 1 results in a quasi-three-dimensional network. The structure of 3 was found to be three-dimensional, where all of the cyano ligands are involved in bridging between the metal centers. The bridging character of the cyano is confirmed spectroscopically. The magnetic properties have been investigated for all of the bimetallic systems. Compound 1 shows ferromagnetic behavior with an ordering temperature at 25 K, which is higher than the corresponding Prussian Blue analogue Co(x)[Fe(CN)(6)](y) ·zH(2)O. Compound 2 shows weak ferromagnetic behavior and an interlayer antiferromagnetic character, while 3, as expected, shows paramagnetic character due to the diamagnetic character of Zn(2+). Compound 4 shows antiferromagnetic behavior.

The unexpected role of pyridine-2-carboxylic acid in manganese based oxidation catalysis with pyridin-2-yl based ligands.

A number of manganese-based catalysts employing ligands whose structures incorporate pyridyl groups have been reported previously to achieve both high turnover numbers and selectivity in the oxidation of alkenes and alcohols, using H(2)O(2) as terminal oxidant. Here we report our recent finding that these ligands decompose in situ to pyridine-2-carboxylic acid and its derivatives, in the presence of a manganese source, H(2)O(2) and a base. Importantly, the decomposition occurs prior to the onset of catalysed oxidation of organic substrates. It is found that the pyridine-2-carboxylic acid formed, together with a manganese source, provides for the observed catalytic activity. The degradation of this series of pyridyl ligands to pyridine-2-carboxylic acid under reaction conditions is demonstrated by (1)H NMR spectroscopy. In all cases the activity and selectivity of the manganese/pyridyl containing ligand systems are identical to that observed with the corresponding number of equivalents of pyridine-2-carboxylic acid; except that, when pyridine-2-carboxylic acid is used directly, a lag phase is not observed and the efficiency in terms of the number of equivalents of H(2)O(2) required decreases from 6-8 equiv. with the pyridin-2-yl based ligands to 1-1.5 equiv. with pyridine-2-carboxylic acid.

Improving the compatibility of fullerene acceptors with fluorene-containing donor-polymers in organic photovoltaic devices.

Fluorene-containing PCBM analogs have been synthesized and tested with a polyfluorene copolymer, PF10TBT, in organic photovoltaic devices resulting in an increase of ∼130 mV in the open circuit voltage compared to devices with PCBM as acceptor material.

Synthesis and structure of an aminoethyl-functionalized cyclopentadienyl vanadium(I) dinitrogen complex.

Reduction of a V(III) complex [(eta(5),eta(1)-C(5)H(4)CH(2)CH(2)NMe(2))VCl(2)(PMe(3))] in the presence of diphenylacetylene under nitrogen atmosphere yields a novel V(I) dinitrogen-bridged complex {[eta(5)-(C(5)H(4)CH(2)CH(2)NMe(2))]V(PhC[triple bond]CPh)(PMe(3))}(2)(mu-N(2)).

Diorganotin(IV) derivatives of ONO tridentate Schiff base: synthesis, crystal structure, in vitro antimicrobial, anti-leishmanial and DNA binding studies.

Six new diorganotin(IV) derivatives of N'-(2-hydroxybenzylidene)formohydrazide (H(2)L) with general formula R(2)SnL, where R = Ph (1), Me (2), Bu (3), Oct (4), t-Bu (5), Et (6), and L = [OC(6)H(4)CHNNCHO] have been synthesized and characterized by different analytical techniques. Crystal structure of Me(2)SnL (2) authenticated distorted square-pyramidal geometry around the Sn atom. The CV and UV-Vis spectroscopic data indicated intercalation of complexes into DNA with binding affinity varying in the sequence: 3 (1.69 x 10(4) M(-1)) > 1 (1.10 x 10(4) M(-1)) > 2 (9.61 x 10(3) M(-1)). Some of these compounds were found to be good antibacterial, antifungal and leishmanicidal agents.

Tuning of the charge in octahedral ferric complexes based on pyridoxal-N-substituted thiosemicarbazone ligands.

Four novel mononuclear coordination compounds namely: [Fe(Hthpy)(2)](SO(4))(1/2).3.5H(2)O , [Fe(Hthpy)(2)]NO(3).3H(2)O , [Fe(H(2)mthpy)(2)](CH(3)C(6)H(4)SO(3))(3).CH(3)CH(2)OH and [Fe(Hethpy)(ethpy)].8H(2)O , (H(2)thpy = pyridoxalthiosemicarbazone, H(2)mthpy = pyridoxal-4-methylthiosemicarbazone, H(2)ethpy = pyridoxal-4-ethylthiosemicarbazone), were synthesized in the absence or presence of organic base, Et(3)N and NH(3). Compounds and are monocationic, and were prepared using the singly deprotonated form of pyridoxalthiosemicarbazone. Both compounds crystallise in the monoclinic system, C2/c and P2(1)/c space group for and , respectively. Complex is tricationic, it is formed with neutral bis(ligand) complex and possesses an interesting 3D channel architecture, the unit cell is triclinic, P1[combining macron] space group. For complex , the pH value plays an important role during its synthesis; is neutral and crystallises with two inequivalent forms of the ligand: the singly and the doubly deprotonated chelate of H(2)ethpy, the unit cell is monoclinic, C2/c space group. Notably, in and , there is an attractive infinite three dimensional hydrogen bonding network in the crystal lattice. Magnetic measurements of and revealed that a rather steep spin transition from the low spin to high spin Fe(iii) states occurs above 300 K in the first heating step. This transition is accompanied by the elimination of solvate molecules and thus, stabilizes the high spin form due to the breaking of hydrogen bonding networks; compared to and , which keep their low spin state up to 400 K.

An enantioselective synthetic route toward second-generation light-driven rotary molecular motors.

Controlling the unidirectional rotary process of second-generation molecular motors demands access to these motors in their enantiomerically pure form. In this paper, we describe an enantioselective route to three new second-generation light-driven molecular motors. Their synthesis starts with the preparation of an optically active alpha-methoxy-substituted upper-half ketone involving an enzymatic resolution. The subsequent conversion of this ketone to the corresponding hydrazone by treatment with hydrazine led to full racemization. However, conversion to a TBDMS-protected hydrazone by treatment with bis-TBDMS hydrazine, prepared according to a new procedure, proceeds with nearly full retention of the stereochemical integrity. Oxidation of the TBDMS-protected hydrazone and subsequent coupling to a lower-half thioketone followed by recrystallization provided the molecular motors with >99% ee. As these are the first molecular motors that have a methoxy substituent at the stereogenic center, the photochemical and thermal isomerization steps involved in the rotary cycle of one of these new molecules were studied in detail with various spectroscopic techniques.

Ultrafast light-driven nanomotors based on an acridane stator.

A series of molecular motors featuring a symmetrical acridane stator is reported. Photochemical and thermal isomerization experiments confirm that this stator, in combination with a thiopyran rotor, results in molecular rotary motion in which the rate-determining thermal helix inversion proceeds effectively only at temperatures above 373 K. The introduction of a cyclopentanylidene rotor unit results in a decrease in steric hindrance with respect to the stator, and as a consequence, a 10(12)-fold increase in the rate of thermal helix inversion is observed. Nanosecond transient absorption spectroscopy allows for the thermal processes to be followed accurately at ambient temperature. The rotary motor is shown to be able to operate at 0.5 MHz rotational frequencies under optimal conditions.

Fast racemisation of chiral amines and alcohols by using cationic half-sandwich ruthena- and iridacycle catalysts.

The lipase-catalysed resolution of alcohols and amines yields only 50 % of the desired enantiopure product. However, addition of a racemisation catalyst leads to 100 % yield in what is called a dynamic kinetic resolution (DKR). There is a need for new racemisation catalysts that are fast and compatible with the conditions of the enzymatic reaction. We show that cationic half-sandwich ruthena- and iridacycle complexes are highly active and efficient in the racemisation of chiral alcohols and amines. Upon activation with base, these complexes are able to selectively racemise alcohols, whereas the non-activated complexes are selective catalysts for the racemisation of amines. We have applied the iridacycles in the DKR of racemic beta-chloroalcohols to produce chiral epoxides in a biphasic system in good yields and high ee (ee=enantiomeric excess).