N,N'-Bis[2,6-bis-(1-methyl-eth-yl)phen-yl]pyridine-4-carboximidamide toluene hemisolvate.

The title compound, C30H39N3·0.5C7H8, is a symmetrically N,N'-disubstituted aryl-amidine containing a 4-pyridyl substituent on the carbon atom of the N-C-N linkage and bulky 2,6-diiso-propyl-phenyl groups on the nitro-gen atoms. It crystallizes in the Z-anti configuration and its amidine C-N bonds present amine [1.368 (1) Å] and imine [1.286 (1) Å] features. Intra-molecular hydrogen bonds are present in the structure together with inter-molecular N-H⋯N and C-H⋯N inter-actions linking the mol-ecules in chains along the a- and c-axis directions.

An earth-abundant system for light-driven CO2 reduction to CO using a pyridinophane iron catalyst.

Herein we report an earth-abundant photocatalytic system for CO2 reduction to CO based on an iron catalyst combined with a CuI photosensitizer. Under visible light irradiation CO is produced as the main product (TONCO = 565, TOFmaxCO = 114 h-1) with a high selectivity over H2 production (SelCO2 = 84%).

Alkyl chain length effects on double-deck assembly at a liquid/solid interface.

Controlled double-deck packing is an appealing means to expand upon conventional 2D self-assembly which is critical in crystal engineering, yet it is rare and poorly understood. Herein, we report the first systematic study of double-deck assembly in a series of alkylated aminoquinone derivatives at the liquid-solid interface. The competition between the fraction of alkyl chains adsorbed on the surface and the optimal conformation of the alkyl chains near the head group leads to a stepwise structural transformation ranging from complete double-deck packing to complete monolayer packing. Alkyl chains on the bottom or top layer of the double-deck assemblies were selectively visualized by carefully tuning the scanning tunneling microscopy settings. A method to easily identify mirror image domains was discovered based on the coincidence of domain boundaries with a graphite main axis. The effect of molecular symmetry and metal complexation on the formation of the double-deck assembly was also explored. Based on 2D crystal engineering principles, this bottom-up double-deck assembly can potentially provide an essential toehold for constructing precise 3D hierarchical structures.

Azadipyrromethene cyclometalation in neutral Ru(II) complexes: photosensitizers with extended near-infrared absorption for solar energy conversion applications.

In the on-going quest to harvest near-infrared (NIR) photons for energy conversion applications, a novel family of neutral ruthenium(ii) sensitizers has been developed by cyclometalation of an azadipyrromethene chromophore. These rare examples of neutral ruthenium complexes based on polypyridine ligands exhibit an impressive panchromaticity achieved by the cyclometalation strategy, with strong light absorption in the 600-800 nm range that tails beyond 1100 nm in the terpyridine-based adducts. Evaluation of the potential for Dye-Sensitized Solar Cells (DSSC) and Organic Photovoltaic (OPV) applications is made through rationalization of the structure-property relationship by spectroscopic, electrochemical, X-ray structural and computational modelization investigations. Spectroscopic evidence for photo-induced charge injection into the conduction band of TiO2 is also provided.

Geometry and Spin Change at the Heart of a Cobalt(II) Complex: A Special Case of Solvatomorphism.

Structural analysis and spectroscopic methods revealed a special case of solvatomorphism: hydrogen-bonding-induced geometry and spin change within a same N,O-(bis)chelate of cobalt(II). Solid-state structures are presented for both the tetrahedral and the solvated square-planar forms of the complex. Magnetic-moment measurements and ESR spectroscopy confirmed the high-spin state of the tetrahedral form (µeff =4.7 µB ) and the low-spin state of the square-planar solvatomorph. Specific hydrogen-bonding interactions between the solvent molecules and the complex chelate ring (O1⋅⋅⋅H-CHCl2 (d=2.26 Å, D=3.24 Å, θ=173°); O2⋅⋅⋅H-CHCl2 (d=2.22 Å, D=3.19 Å, θ=165°)) play a pivotal role in biasing the system toward the low-spin ground state.

Two fac-tricarbonylrhenium(I) azadipyrromethene (ADPM) complexes: ligand-substitution effect on crystal structure.

The crystal structures of fac-(acetonitrile-κN)(2-{[3,5-bis(4-methoxyphenyl)-2H-pyrrol-2-ylidene-κN(1)]amino}-3,5-bis(4-methoxyphenyl)-1H-pyrrol-1-ido-κN(1))tricarbonylrhenium(I)-hexane-acetonitrile (2/1/2), [Re(C36H30N3O4)(CH3CN)(CO)3]·0.5C6H14·CH3CN, (2), and fac-(2-{[3,5-bis(4-methoxyphenyl)-2H-pyrrol-2-ylidene-κN(1)]amino}-3,5-bis(4-methoxyphenyl)-1H-pyrrol-1-ido-κN(1))tricarbonyl(dimethyl sulfoxide-κO)rhenium(I), [Re(C36H30N3O4)(C2H6OS)(CO)3], (3), at 150 K are reported. Both complexes display a distorted octahedral geometry, with a fac-Re(CO)3 arrangement and one azadipyrromethene (ADPM) chelating ligand in the equatorial position. One solvent molecule completes the coordination sphere of the Re(I) centre in the remaining axial position. The ADPM ligand shows high flexibility upon coordination, while retaining its π-delocalized nature. Bond length and angle analyses indicate that the differences in the geometry around the Re(I) centre in (2) and (3), and those found in three reported fac-Re(CO)3-ADPM complexes, are dictated mainly by steric factors and crystal packing. Both structures display intramolecular C-H...N hydrogen bonding. Intermolecular interactions of the Csp(2)-H...π and Csp(2)-H...O(carbonyl) types link the discrete monomers into extended chains.

Introducing asymmetry in tetradentate azadipyrromethene chromophores: a systematic study of the impact on electronic and photophysical properties.

As analogues of the porphyrinoid and dipyrromethene families of dye, azadipyrromethene (ADPM) derivatives exhibit exciting photophysical properties. Their high absorbance (ε up to 100,000 M(-1) cm(-1)) in the yellow-to-red region and the strong NIR luminescence encountered in boron-chelated aza-BODIPY analogues are especially interesting in the context of light-harvesting and life science applications. In the present study, we endeavoured to compare symmetric and asymmetric tetradentate ADPM derivatives 1-6 versus two related bidentate ADPM references in order to gain insights into their structure-property relationship. This is of interest since the tetradentate motif opens the way for extended π-conjugation through metal-mediated planarization, in a bio-mimicry fashion of metalloporphyrinoids, and is known to induce a bathochromic shift toward the NIR. A new straightforward synthetic approach is used to access asymmetric derivatives 4-6 that avoids the tedious heterocycle formation of nitroso-pyrrole intermediates. In addition, photophysics, electrochemistry, computational modelization (DFT and TD-DFT) and X-ray structural characterization of ADPMs are used to better understand the potential of these new chromophores.

N-[2,6-Bis(1-methyl-eth-yl)phen-yl]pyridine-4-carboxamide.

In the title compound, C(18)H(22)N(2)O, the dihedral angle between the benzene ring and the pyridine ring is 80.0 (1)°. In the crystal, N-H⋯O hydrogen bonds connect the mol-ecules into chains along the b axis. The packing also features C-H⋯O and C-H⋯N hydrogen bonds and C-H⋯π interactions, one directed to the benzene ring and the other to the center of the pyridine ring.

Synthesis and crystal structure of a rare square-planar Co(II) complex of a hydroxyamidinate ligand.

Novel hydroxyamidinate complexes of cobalt(II) are presented, together with their electrochemical and spectroscopic properties. An unusual d(7) square-planar coordination around the cobalt(II) center exists and was confirmed by chemical oxidation to its Co(III) species. The Co(II) complex is difficult to reduce, but its facile oxidation suggests that it may be useful as an electron donor in photoredox reactions.

8-(Diphenyl-phosphan-yl)quinoline.

The title compound, C(21)H(16)NP, is a known P-N chelator and various crystal structures of its metal complexes have been reported. However, no crystallographic evidence of the free ligand has been given to date. The phenyl rings are almost orthogonal to one another [dihedral angle = 88.9 (1)°], and they are twisted from the mean plane of the quinoline by 80.5 (1) and 76.3 (1)°.

N,N-Bis-(2,6-di-methyl-phen-yl)-N-hydroxyformamidine N,N'-bis-(2,6-dimethyl-phen-yl)-N-oxidoformamidinium dichloro-methane solvate.

The title compound, 2C(17)H(20)N(2)O·CH(2)Cl(2), was obtained by N-oxidation of the parent formamidine with m-chloro-peroxy-benzoic acid (m-CPBA). This is the first use of the above-mentioned synthetic route for the preparation of hydroxy-amidines. The title compound crystallizes as a cyclic dimer resulting from the presence of O-H⋯O and N-H⋯N hydrogen bonds.

4-Bromo-N-phenyl-benzamidoxime.

The title compound, C(13)H(11)BrN(2)O, a hydroxy-amidine derivative (an amidoxime), was obtained by addition of the corresponding imidoyl chloride to hydroxy-lamine. The benzene and phenyl rings are twisted from the mean plane of the hydroxy-amidine group by 34.4 (1) and 59.2 (1)°, respectively. In the crystal structure, inter-molecular O-H⋯N hydrogen bonds link pairs of mol-ecules, forming centrosymmetric dimers.