Supramolecular architecture of theophylline polymorphs, monohydrate and co-crystals with iodine: study from the energetic viewpoint

The regularities of crystal structure organization were thoroughly studied in all to date known polymorphic modifications of theophylline (THP) using an energetic approach. The monohydrate and a co-crystal of theophylline with one half equivalent of an iodine molecule were similarly investigated. The calculations of pairwise interaction energies have showed that the crystals studied can be divided into two groups according to their basic structural motifs: columnar-layered or columnar. The energetic approach also allows the role of different interactions in the crystal structure formation to be estimated. It was found that strong N-H⋯N, N-H⋯O hydrogen bonds and stacking interactions play the most important roles in polymorphic modifications of THP and the THP monohydrate. In the case of the co-crystal with iodine, N-H⋯O hydrogen bond participates in the dimeric building unit formation. However, instead of a stacking interaction the π⋯π interaction between carbonyl groups of neighboring molecules plays the highest role in the supramolecular architecture of this crystal. The lattice energies calculations in periodic conditions for polymorphic structures have shown that polymorph with the most anisotropic energetic structure may be considered as stable and all others forms metastable. In the polymorphic modification 1 of THP a zwitter-ionic resonance form is predominant, which affects significantly the solubility and the intermolecular interactions of this modification.

An I 6 2 − ${\mathrm{I}}_{6}^{2-}$ anion in the crystal structure of theophyllinium triiodide monohydrate, C7H11I3N4O3

C7H11I3N4O3, triclinic, P 1 ‾ $P\overline{1}$ (no. 2), a = 9.28478(14) Å, b = 12.2214(2) Å, c = 13.4088(2) Å, α = 76.2062(14)°, β = 88.2421(13)°, γ = 89.4102(13)°, Z = 4, V = 1476.95(4) Å3, Rgt(F) = 0.0198, wR ref = 0.0494, T = 100 K.

Cones with a three-fold symmetry constructed from three hydrogen bonded theophyllinium cations that coat [FeCl4]− anions in the crystal structure of tris(theophyllinium) bis(tetrachloridoferrate(III)) chloride trihydrate, C21H33Cl9Fe2N12O9

C21H33Cl9Fe2N12O9, trigonal, R 3 ‾ $R\overline{3}$ (no. 148), a = 13.1897(3) Å, c = 39.5222(9) Å, Z = 6, V = 5954.4(3) Å3, R gt (F) = 0.0255, wR ref (F 2) = 0.0743, T = 120 K.

The layered crystal structure of bis(theophyllinium) hexachloridostannate (IV), C14H18N8O8SnCl6

C14H18N8O8SnCl6, monoclinic, P21/n (no. 14), a = 8.1810(2) Å, b = 12.6195(3) Å, c = 11.3811(2) Å, β = 90.258(2)°, Z = 2, V = 1174.97(5) Å3, R gt(F) = 0.0266, wR ref = 0.0620, T = 290 K.

Facile Synthesis of Bio-Antimicrobials with "Smart" Triiodides

Multi-drug resistant pathogens are a rising danger for the future of mankind. Iodine (I₂) is a centuries-old microbicide, but leads to skin discoloration, irritation, and uncontrolled iodine release. Plants rich in phytochemicals have a long history in basic health care. Aloe Vera Barbadensis Miller (AV) and Salvia officinalis L. (Sage) are effectively utilized against different ailments. Previously, we investigated the antimicrobial activities of smart triiodides and iodinated AV hybrids. In this work, we combined iodine with Sage extracts and pure AV gel with polyvinylpyrrolidone (PVP) as an encapsulating and stabilizing agent. Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-Vis), Surface-Enhanced Raman Spectroscopy (SERS), microstructural analysis by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-Ray-Diffraction (XRD) analysis verified the composition of AV-PVP-Sage-I₂. Antimicrobial properties were investigated by disc diffusion method against 10 reference microbial strains in comparison to gentamicin and nystatin. We impregnated surgical sutures with our biohybrid and tested their inhibitory effects. AV-PVP-Sage-I₂ showed excellent to intermediate antimicrobial activity in discs and sutures. The iodine within the polymeric biomaterial AV-PVP-Sage-I₂ and the synergistic action of the two plant extracts enhanced the microbial inhibition. Our compound has potential for use as an antifungal agent, disinfectant and coating material on sutures to prevent surgical site infections.

Antimicrobial Hexaaquacopper(II) Complexes with Novel Polyiodide Chains

The non-toxic inorganic antimicrobial agents iodine (I2) and copper (Cu) are interesting alternatives for biocidal applications. Iodine is broad-spectrum antimicrobial agent but its use is overshadowed by compound instability, uncontrolled iodine release and short-term effectiveness. These disadvantages can be reduced by forming complex-stabilized, polymeric polyiodides. In a facile, in-vitro synthesis we prepared the copper-pentaiodide complex [Cu(H2O)6(12-crown-4)5]I6 · 2I2, investigated its structure and antimicrobial properties. The chemical structure of the compound has been verified. We used agar well and disc-diffusion method assays against nine microbial reference strains in comparison to common antibiotics. The stable complex revealed excellent inhibition zones against C. albicans WDCM 00054, and strong antibacterial activities against several pathogens. [Cu(H2O)6(12-crown-4)5]I6 · 2I2 is a strong antimicrobial agent with an interesting crystal structure consisting of complexes located on an inversion center and surrounded by six 12-crown-4 molecules forming a cationic substructure. The six 12-crown-4 molecules form hydrogen bonds with the central Cu(H2O)6. The anionic substructure is a halogen bonded polymer which is formed by formal I5- repetition units. The topology of this chain-type polyiodide is unique. The I5- repetition units can be understood as a triodide anion connected to two iodine molecules.

Hydrogen bonding versus packing effects in the crystal structure of 3-((1R,2S)-1-methylpyrrolidin-1-ium-2-yl)pyridin-1-ium tetraiodidozincate(II), C10H16I4ZnN2

C10H16I4ZnN2, monoclinic, P21 (no. 4), a = 7.3340(1) Å, b = 14.4781(3) Å, c = 8.6768(2) Å, β = 94.919(2)°, V = 917.93(3) Å3, Z = 2, R gt(F) = 0.0165, wR ref(F 2) = 0.0397, T = 110 K.

The crystal structure of 3-((1R,2S)-1-methylpyrrolidin-1-ium-2-yl)pyridin-1-ium tetrachloridozincate(II) monohydrate, C10H18Cl4ZnN2O

C10H18Cl4ZnN2O, orthorhombic, P212121 (no. 19), a = 7.0752(1) Å, b = 7.5085(1) Å, c = 29.3383(5) Å, V = 1558.57(4) Å3, Z = 4, R gt(F) = 0.0330, wR ref(F 2) = 0.0672, T = 290(2) K.

Crystal structure of bis(1,3-phenylenedimethanaminium) bis(triiodide) tetraiodide – water (1/2) , C8H16I5N2O

C8H16I5N2O, monoclinic, C2/c (no. 15), a = 34.180(5) Å, b = 7.6817(3) Å, c = 21.421(3) Å, β = 137.93(3)°, Z = 8, V = 3768.7(16) Å3, Rgt(F) = 0.0364, wR ref = 0.0737, T = 290(2) K.

Crystal structure and antimicrobial properties of (1,4,7,10-tetraoxacyclododecane-κ4 O,O′,O′′,O′′′)cesium(I) pentaiodide, C16H32CsI5O8

C16H32CsI5O8, monoclinic, I2/a (no. 15), a = 16.386(2) Å, b = 11.7050(10) Å, c = 19.005(3) Å, β = 108.008(14)°, V = 3466.6(8) Å3, Z = 4, R gt(F) = 0.0437, wR ref(F 2) = 0.1085, T = 293(2) K.

The crystal structure of 3-((1R,2S)-1-methylpyrrolidin-1-ium-2-yl)pyridin-1-ium tetrachloridomanganate(II), C10H16Cl4MnN2

C10H16Cl4MnN2, monoclinic, P21 (no. 4), a = 7.28276(7) Å, b = 13.22972(12) Å, c = 8.01007(7) Å, β = 97.5018(9)°, V = 765.155(12) Å3, Z = 2, Rgt(F) = 0.0165, wRref(F2) = 0.0392, T = 123(2) K.

Halogen bonding in crystal structure of bis(1,4,7,10-tetraoxacyclododecane-κ4O,O′,O′′,O′′′)cesium triiodide, C16H32CsI3O8

C16H32CsI3O8, triclinic, P1̄ (no. 2), a = 10.7930(5) Å, b = 11.5610(5) Å, c = 12.4880(5) Å, α = 73.050(10)°, β = 88.870(10)°, γ = 66.060(10)°, V = 1353.62(16) Å3, Z = 2, R gt(F) = 0.0578, wR ref(F 2) = 0.1875, T = 293(2) K.

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

ortho-Fluoroazobenzenes are a remarkable example of bistable photoswitches, addressable by visible light. Symmetrical, highly fluorinated azobenzenes bearing an iodine substituent in para-position were shown to be suitable supramolecular building blocks both in solution and in the solid state in combination with neutral halogen bonding acceptors, such as lutidines. Therefore, we investigate the photochemistry of a series of azobenzene photoswitches. Upon introduction of iodoethynyl groups, the halogen bonding donor properties are significantly strengthened in solution. However, the bathochromic shift of the π→π* band leads to a partial overlap with the n→π* band, making it slightly more difficult to address. The introduction of iodine substituents is furthermore accompanied with a diminishing thermal half-life. A series of three azobenzenes with different halogen bonding donor properties are discussed in relation to their changing photophysical properties, rationalized by DFT calculations.