Structural and Thermal Studies of New Triphenyltin Complexes.

Crystal and molecular structures of new triorganotin complexes have been determined via X-ray diffraction. These complexes include, among others, the second polymorph of Ph3Sn(thiocytosine), the double complex salt Ph3Sn(methimazole)2·Ph3SnCl2, and five-coordinated triphenyltin chloride with methimazole, tetrahydopyrimidine-2-thione, dimethylformamide, and dimethyl sulfoxide. Hirshfeld surface analysis allowed for better visualization and precise pinpointing of the differences between polymorphs as well as easier analysis of intermolecular interactions. All of the new structure of the Ph3Sn(L)Cl type displayed interesting thermal features and therefore were also analyzed via thermogravimetric analysis/simultaneous thermal analysis/differential scanning calorimetry methods. These analyses showed the different ways in which these complexes underwent thermal decomposition. In some cases, to solve the problems that arose, powder X-ray diffraction analyses have also been performed.

Relations between Structural and Luminescence Properties of Novel Lanthanide Nitrate Complexes with Bis-phosphoramidate Ligands.

Five new bisphosphoramide-based LnIII nitrate complexes [La2(NO3)6L3I] n (1), [Ce2(NO3)6L3I] n (2), [Sm2(NO3)6L3II] n (3), Sm2(NO3)6L3III (4), and Er(NO3)3L2III (5) [LI = piperazine-1,4-diylbis(diphenyl phosphine oxide), LII = N, N'-(ethane-1,2-diyl)bis( N-methyl- P, P-diphenylphosphinic amide, and LIII = N, N'-(ethane-1,2-diyl)bis( P, P-diphenylphosphinic amide)] have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), and single crystal X-ray and powder diffractions. The results of the X-ray diffraction analysis revealed the new polymorph of LIII, and the structural diversity of the synthesized complexes in the solid state. Complexes 1-3 display two-dimensional coordination polymers (2D-CP), containing layers with honeycomb (6, 3) topology. In these 2D-CPs, each Ln center (La, Ce, and Sm in 1, 2, and 3, respectively) could be considered as a triconnected node, linked by three bridging bisphosphoramide ligands as two-connecting linkers. In contrast, 4 is a discrete binuclear complex, in which bidentate LIII ligand has two entirely different conformations: the syn chelating and the anti bridging. Cationic complex 5 shows the monomeric structure, where bidentate LIII adopts the syn-chelating conformation. A comprehensive luminescence investigation has been performed on free ligands and their corresponding complexes as well. The synthesized compounds display a variety of luminescence behavior, including the ligand-centered fluorescence in 1, 2, and 5, two distinct emission peaks in 1 and 2, characteristic Sm-centered f-f emission in 3 and 4, and excitation-dependent emission in LIII, 1, and 2. Furthermore, the time-dependent density functional theory (TD-DFT) study was carried out on the reported compounds to understand the nature of the emission peaks and the observed luminescence properties. The solid-state emission quantum yields of lanthanide complexes were also determined at different excitation wavelengths.

Different cationic forms of (-)-cytisine in the crystal structures of its simple inorganic salts.

The crystal structures of 13 simple salts of cytisine, an alkaloid isolated from the seeds of Laburnum anagyroides, have been determined, namely cytisinium (6-oxo-7,11-diazatricyclo[7.3.1.02,7]trideca-2,4-dien-11-ium) bromide, C11H15N2O+·Br-, cytisinium iodide, C11H15N2O+·I-, cytisinium perchlorate, C11H15N2O+·ClO4-, cytisinium iodide triiodide, C11H15N2O+·I-·I3-, cytisinium chloride monohydrate, C11H15N2O+·Cl-·H2O, cytisinium iodide monohydrate, C11H15N2O+·I-·H2O, cytisinium nitrate monohydrate, C11H15N2O+·NO3-·H2O, hydrogen dicytisinium tribromide, C22H31N4O23+·3Br-, hydrogen dicytisinium triiodide, C22H31N4O23+·3I-, hydrogen dicytisinium triiodide diiodide, C22H31N4O23+·I3-·2I-, hydrogen dicytisinium bis(triiodide) iodide, C22H31N4O23+·2I3-·I-, cytisinediium (6-oxidaniumylidene-7,11-diazatricyclo[7.3.1.02,7]trideca-2,4-dien-11-ium) bis(perchlorate), C11H16N2O2+·2ClO4-, and cytisinediium dichloride trihydrate, C11H16N2O2+·2Cl-·3H2O. Cytisine has two potential protonation sites, i.e. the N atom of the piperidine ring and the carbonyl O atom of the pyridone ring. Three forms of the cytisinium cation were identified, namely the monocation, which is always protonated at the N atom, the dication, which utilizes both protonation sites, and the third form, which contains two cytisine moieties connected by very short and linear O...H...O hydrogen bonds, with an O...O distance of approximately 2.4 Å. This third form may therefore be regarded as a 3+ species, or sesqui-cation, and is observed solely in the salts with bromide, iodide or triiodide (heavier halogen) anions. The cation is quite rigid and all 19 cytisinium fragments in the studied series have very similar conformations. The crystal structures are determined mainly by Coulombic interactions and hydrogen bonds, and the latter form is determined by different networks. Additionally, some anion-π and lone-pair...π secondary interactions are identified in almost all of the crystal structures. Hirshfeld surface analysis generally confirms the role of different interactions in the determination of the crystal architecture.

A new class of silica-supported chromo-fluorogenic chemosensors for anion recognition based on a selenourea scaffold.

The first example of a chemosensor (L) containing a selenourea moiety is described here. L is able to colorimetrically sense the presence of CN- and S2- in H2O : MeCN (75 : 25, v/v). Moreover, when L is loaded into functionalised mesoporous silica nanoparticles an increase in the selectivity towards S2- occurs via a selective fluorescence response.