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A Cu^IIcoordination polymer,catena-poly[[[aquacopper(II)]-bis(μ-4-aminobenzoato)-κ²N:O;κ²O:N] monohydrate], {[Cu(pABA)₂(H₂O)]·H₂O}_n(pABA =p-aminobenzoate, C₇H₄NO₂⁻), was synthesized and characterized. It exhibits a one-dimensional chain structure extended into a three-dimensional supramolecular assembly through hydrogen bonds and π–π interactions. While the twinned crystal shows a metrically orthorhombic lattice and an apparent space groupPbcm, the true symmetry is monoclinic (space groupP2/c), with disordered Cu atoms and mixed roles of water molecules (aqua ligand/crystallization water). The luminescence spectrum of the complex shows an emission at 345 nm,cf.349 nm forpABAH.

 

For a series of substituted dithieno[3,2-a:2′,3′-c]phenazine derivatives X-ray diffraction studies have been carried out.

 

Structures of three cocrystals of nootropic racetams were studied. They included two cocrystals of phenylpiracetam (PPA) with 4-hydroxybenzoic acid (HBA) with different stoichiometries, PPA·HBA and PPA·2HBA, and cocrystal of 2-(4-phenyl-2-oxopyrrolidin-1-yl)-N’-isopropylideneacetohydrazide (PPAH) with 4-hydroxybenzamide (HBD), PPAH·HBD·(acetone solvate). X-ray study of the pure forms of PPA and PPAH was also carried out to identify variations of molecular synthons under the influence of conformers. The cocrystal structures revealed the diversity of supramolecular synthons namely, amide-amide, amide-acid, acid-acid, and hydroxyl-hydroxyl; however, very similar molecular chains were found in PPA and PPA·2HBA, and similar molecular dimers in PPAH and PPAH·HBD. In addition, conformational molecular diversity was observed as disorder in PPA·2HBA as it was observed earlier for rac-PPA that allows for the consideration that cocrystal as an example of partial solid solution. Quantum chemical calculations of PPA and PPAH conformers demonstrated that for most conformers, energy differences do not exceed 2 kcal/mol that suggests the influence of packing conditions (in this case R- and S-enantiomers intend to occupy the same molecular position in crystal) on molecular conformation. 

1,3-Dimethyl-2,3-dihydrobenzo[d]imidazoles,1H, and 1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d]imidazoles,1₂, are of interest as n-dopants for organic electron-transport materials. Salts of 2-(4-(dimethylamino)phenyl)-4,7-dimethoxy-, 2-cyclohexyl-4,7-dimethoxy-, and 2-(5-(dimethylamino)thiophen-2-yl)benzo[d]imidazolium (1g–i⁺, respectively) have been synthesized and reduced with NaBH₄to1gH,1hH, and1iH, and with Na:Hg to1g₂and1h₂. Their electrochemistry and reactivity were compared to those derived from 2-(4-(dimethylamino)phenyl)- (1b⁺) and 2-cyclohexylbenzo[d]imidazolium (1e⁺) salts.E(1⁺/1^•) values for 2-aryl species are less reducing than for 2-alkyl analogues, i.e., the radicals are stabilized more by aryl groups than the cations, while 4,7-dimethoxy substitution leads to more reducingE(1⁺/1^•) values, as well as cathodic shifts inE(1₂^•+/1₂) andE(1H^•+/1H) values. Both the use of 3,4-dimethoxy and 2-aryl substituents accelerates the reaction of the1Hspecies with PC₆₁BM. Because 2-aryl groups stabilize radicals,1b₂and1g₂exhibit weaker bonds than1e₂and1h₂and thus react with 6,13-bis(triisopropylsilylethynyl)pentacene (VII) via a “cleavage-first” pathway, while1e₂and1h₂react only via “electron-transfer-first”.1h₂exhibits the most cathodicE(1₂^•+/1₂) value of the dimers considered here and, therefore, reacts more rapidly than any of the other dimers withVIIvia “electron-transfer-first”. Crystal structures show rather long central C–C bonds for1b₂(1.5899(11) and 1.6194(8) Å) and1h₂(1.6299(13) Å).

 

A new pseudopolymorph of berberine, 9,10-dimethoxy-5,6-dihydro-2 H -7λ 5 -[1,3]dioxolo[4,5- g ]isoquinolino[3,2- a ]isoquinolin-7-ylium chloride methanol monosolvate, C 20 H 18 NO 4 + ·Cl − ·CH 3 OH, was obtained during co-crystallization of berberine chloride with malonic acid from methanol. The berberine cations form dimers, which are further packed in stacks. The title structure was compared with other reported solvates of berberine chloride: its dihydrate, tetrahydrate, and ethanol solvate hemihydrate. Hirshfeld analysis was performed to show the intermolecular interactions in the crystal structure of the title compound, and its fingerprint plots were compared with those of the already studied solvates. 

[RuCp*(1,3,5-R 3 C 6 H 3 )] 2 {Cp* = η 5 -pentamethylcyclopentadienyl, R = Me, Et} have previously been found to be moderately air stable, yet highly reducing, with estimated D + /0.5D 2 (where D 2 and D + represent the dimer and the corresponding monomeric cation, respectively) redox potentials of ca. −2.0 V vs. FeCp 2 +/0 . These properties have led to their use as n-dopants for organic semiconductors. Use of arenes substituted with π-electron donors is anticipated to lead to even more strongly reducing dimers. [RuCp*(1-(Me 2 N)-3,5-Me 2 C 6 H 3 )] + PF 6 − and [RuCp*(1,4-(Me 2 N) 2 C 6 H 4 )] + PF 6 − have been synthesized and electrochemically and crystallographically characterized; both exhibit D + /D potentials slightly more cathodic than [RuCp*(1,3,5-R 3 C 6 H 3 )] + . Reduction of [RuCp*(1,4-(Me 2 N) 2 C 6 H 4 )] + PF 6 − using silica-supported sodium–potassium alloy leads to a mixture of isomers of [RuCp*(1,4-(Me 2 N) 2 C 6 H 4 )] 2 , two of which have been crystallographically characterized. One of these isomers has a similar molecular structure to [RuCp*(1,3,5-Et 3 C 6 H 3 )] 2 ; the central C–C bond is exo , exo , i.e. , on the opposite face of both six-membered rings from the metals. A D + /0.5D 2 potential of −2.4 V is estimated for this exo , exo dimer, more reducing than that of [RuCp*(1,3,5-R 3 C 6 H 3 )] 2 (−2.0 V). This isomer reacts much more rapidly with both air and electron acceptors than [RuCp*(1,3,5-R 3 C 6 H 3 )] 2 due to a much more cathodic D 2 ˙ + /D 2 potential. The other isomer to be crystallographically characterized, along with a third isomer, are both dimerized in an exo , endo fashion, representing the first examples of such dimers. Density functional theory calculations and reactivity studies indicate that the central bonds of these two isomers are weaker than those of the exo , exo isomer, or of [RuCp*(1,3,5-R 3 C 6 H 3 )] 2 , leading to estimated D + /0.5D 2 potentials of −2.5 and −2.6 V vs. FeCp 2 +/0 . At the same time the D 2 ˙ + /D 2 potentials for the exo , endo dimers are anodically shifted relative to those of [RuCp*(1,3,5-R 3 C 6 H 3 )] 2 , resulting in much greater air stability than for the exo , exo isomer.