Volume 76, Issue 5

The huge number of intermetallic structure types with many representatives calls for structural systemization. The combination of crystal chemistry with group theory is an efficient tool for such systemization and can be displayed in a concise and compact way via group-subgroup schemes. The present overview deals with such group-subgroup schemes (Bärnighausen trees) for coloring and distortion variants of the bcc packing as well as superstructures that derive from the aristotypes BaAl 4 and CeMg 2 Si 2 .

The Re 3 B type, space group Cmcm , has boron-centered trigonal prisms as central building units and is one of the basic structure types with numerous binary and ternary representatives. The coloring of different atoms on the two crystallographically independent rhenium sites leads to a manifold of compounds with different bonding peculiarities that are rather isopointal than isotypic with the prototype. Typical compounds are the S -phase precipitate MgCuAl 2 , the silicide ScPt 2 Si or the iodide Th 0.5 Pb 0.5 I 3 (PuBr 3 type). Differences in size or composition might force symmetry reductions. This is discussed for YZn 3 (space group Pnma ) and the different coloring variants ScRhSi 2 and TaNi 2 P which show different twists of the trigonal prisms. Striking singular representatives with lower symmetry structures are BaThBr 6 ( Pmma ) and NbCo 2 B ( P 2 1 / c ) which allow different ordering/distortion patterns for the prisms. All these crystal chemical details are discussed on the basis of group subgroup schemes (Bärnighausen trees).

14 N magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of diamagnetic LaTiO 2 N perovskite oxynitride and its paramagnetic counterpart CeTiO 2 N are presented. The latter, to the best of our knowledge, constitutes the first high-resolution 14 N MAS NMR spectrum collected from a paramagnetic solid material. The unpaired 4 f -electrons in CeTiO 2 N do not induce a paramagnetic 14 N NMR shift. This is remarkable given the direct Ce−N contacts in the structure for which ab initio calculations predict substantial Ce→ 14 N contact shift interaction. The same effect is revealed with 14 N MAS NMR for SrWO 2 N (unpaired 5 d -electrons).

The lithium ytterbium ortho -thiophosphates Li 9 Yb 2 [PS 4 ] 5 and Li 6 Yb 3 [PS 4 ] 5 were prepared through the reaction of stoichiometric amounts of ytterbium metal, elemental sulfur, red phosphorus and lithium hemisulfide at elevated temperatures in sealed silica tubes. The compounds occur as dark red single crystals which crystallize monoclinically in space group C 2/ c with the lattice parameters a  = 1487.98(9), b  = 978.63(6), c  = 2046.75(12) pm and β  = 96.142(3)° for Li 9 Yb 2 [PS 4 ] 5 ( Z  = 4) and a  = 2814.83(16), b  = 997.34(6), c  = 3338.52(19) pm and β  = 113.685(3)° for Li 6 Yb 3 [PS 4 ] 5 ( Z  = 12). Li 9 Yb 2 [PS 4 ] 5 can be assigned to the structure type of Li 9 Nd 2 [PS 4 ] 5 , whereas the structure of Li 6 Yb 3 [PS 4 ] 5 the structure is similar to that of the prototypic Li 6 Gd 3 [PS 4 ] 5 . Both structures feature discrete [PS 4 ] 3– tetrahedra ( d (P–S) = 202–207 pm) and strands of [YbS 8 ] 13− polyhedra ( d (Yb–S) = 271–319 pm) propagating along [010]. When attributed to the general formula (Li 3 [PS 4 ]) x (Yb[PS 4 ]) y , ideas of the dimensionality of both structures can be derived. Whilst the lithium-richer Li 9 Yb 2 [PS 4 ] 5 ( x/y  = 1.5) develops planes with the composition  ∞2{[Yb[PS4]3]6−}${}_{\infty }^{2}\left\{{\left[\mathrm{Y}\mathrm{b}{\left[\mathrm{P}{\mathrm{S}}_{4}\right]}_{3}\right]}^{6-}\right\}$, Li 6 Yb 3 [PS 4 ] 5 ( x / y  = 0.667) exhibits a rather complex three-dimensional network of ytterbium-centered polyhedra connected via [PS 4 ] 3– tetrahedra with lithium cations in the framework structure  ∞3{[Yb3[PS4]5]6−}${}_{\infty }^{3}\left\{{\left[\mathrm{Y}{\mathrm{b}}_{\mathrm{3}}{\left[\mathrm{P}{\mathrm{S}}_{4}\right]}_{5}\right]}^{6-}\right\}$. These Li + cations are hard to locate in both compounds, but reside in four- to sixfold sulfur coordination ( d (Li–S) = 235–304 pm). Some Li + positions are underoccupied and some Li + cations share sites with Yb 3+ cations in Li 6 Yb 3 [PS 4 ] 5 , and even in Li 9 Yb 2 [PS 4 ] 5 their high displacement values suggest Li + cation mobility. According to the empirical formulae, three Li + cations have to be replaced with one Yb 3+ cation to reach the lithium-poorer compound and structure (Li 6 Yb 3 [PS 4 ] 5 ) starting from the lithium-richer one (Li 9 Yb 2 [PS 4 ] 5 ).

New piperazine-tagged imidazole derivatives were synthesized via reaction of 1-alkyl/aryl-5-bromo-2-alkyl-4-nitro-1 H -imidazoles 1 – 3 with piperazine nucleophiles. Nine selected compounds were assessed for their antiproliferative inhibition potency against five human cancer cell lines (MCF-7, PC3, Du145, HepG2 and Dermal/Fibroblast). Compounds 7 and 10 are the most potent anticancer agents on HepG2 cell line with IC 50 values of (5.6 ± 0.5 µm) and (29.6 ± 7.6 µm) respectively, and on MCF-7 with IC 50 values of (32.1 ± 5.6 µm) and (46.2 ± 8.2 µm) respectively. The molecular docking of compounds 7 and 10 has been studied, and the results reveal that the newly designed piperazine-tagged imidazole derivatives bind to the hydrophobic pocket and polar contact with high affinity.

Pyrazino[1,2- a ]indoles fused with various heterocycles, such as oxazolidine, oxazinane, imidazolidine, hexahydropyrimidine and benzimidazole, were synthesized transition metal-free by domino reactions which involved the condensation of 1-(2-bromoethyl)-3-chloro-1 H -indole-2-carbaldehydes 28 – 31 with various nucleophilic amines, resulting in the formation of two new interesting fused heterocycles. The anticholinesterase, antioxidant and antibacterial activities of the compounds were evaluated. Acetylcholinesterase (AChE) inhibitory activities were tested by Ellman’s assay, antioxidant activities were detected using the 2,2-azinobis[3-ethylbenzthiazoline]-6-sulfonic acid (ABTS •+ ) free-radical scavenging method and antibacterial activities were determined by agar diffusion tests. The oxazolo-pyrazino[1,2- a ]indoles ( 8 , 10 ), the oxazino-pyrazino[1,2- a ]indoles ( 16 , 18 , 19 ), the pyrimido-pyrazino[1,2- a ]indole (22 ), and the benzoimidazo-pyrazino[1,2- a ]indole ( 27 ) possessed the highest inhibitory activity against AChE with IC 50 values in the range 20–40 μg mL −1 . The oxazolo-pyrazino[1,2- a ]indoles ( 8 , 9 ), the imidazo-pyrazino[1,2- a ]indoles ( 12 , 13 ), and the benzoimidazo-pyrazino[1,2- a ]indole ( 24 ) revealed the highest antioxidant values with IC 50 values less than 300 μg mL −1 . However, the oxazolo-pyrazino[1,2- a ]indole ( 11 ) and imidazo-pyrazino[1,2- a ]indoles ( 12 , 13 ) exhibited weak to moderate bioactivities against all tested Gram-positive bacteria, namely Staphylococcus aureus , Bacillus subtilis and Bacillus cereus .

In this work, a new type of zinc(II) coordination polymer {[Zn(HIDC)(BBM) 0.5 ]·H 2 O} n (Zn-CP) was synthesized using 4,5-imidazoledicarboxylic acid (H 3 IDC) and 2,2-(1,4-butanediyl)bis-1,3-benzimidazole (BBM) under hydrothermal conditions. Its structure has been characterized by infrared spectroscopy, elemental analysis and single crystal X-ray diffraction analysis. The Zn(II) ion is linked by the HIDC 2− ligand to form a zigzag chain by chelating and bridging, and then linked by BBM to form a layered network structure. Adjacent layers are further connected by hydrogen bond interaction to form a 3-D supramolecular framework. The solid-state fluorescence performance of Zn-CP shows that compared with free H 3 IDC ligand, its fluorescence intensity is significantly enhanced.

Two coordination polymers [Cd 3 (CPIDA) 2 (bib)(H 2 O) 2 ] n 1 and {[Zn 6 (CPIDA) 4 (bix) 3 ]·8H 2 O} n 2 (H 3 CPIDA =  N -(4-carboxyphenyl) iminodiacetic acid, bib = 1,4-bis(N-imidazolyl)butane, bix = 1,4-bis(imidazol-1-ylmethyl)benzene), have been hydrothermally synthesized and characterized by analytical and IR spectroscopic data. Compound 1 displays an interesting 3D framework with trinodal (4,5)-connected topology, consisting of (4,4) rectangular grid double layers linked by trans- bib ligands. In 2 , the corrugated nets with couples of central symmetrical chains constructed by CPIDA 3− and bridging trans -bix ligands are pillared by infinite tubes made from CPIDA 3− and cis -bix ligands to build a new 3D porous framework with parallelogram-shaped channels, exhibiting a pentanodal (3,4)-connected topology. Moreover, compounds 1 and 2 show intense solid state fluorescence at room temperature.

The two enantiopure chiral organic ligands 2-[( S )-4-isopropyl-2-oxazolyl]quinoline (L 1 ) and 2-[( S )-4-benzyl-2-oxazolyl]quinoline (L 2 ) react with different silver salts to give rise to three new silver complexes [Ag(L 1 ) 2 ](SbF 6 ) ( 1 ), [Ag(L 1 )(CH 3 CN)](ClO 4 ) ( 2 ), and [Ag(L 2 )(NO 3 )] ( 3 ), which have been characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental and thermogravimetric analyses. Complexes 1 – 3 all display discrete mononuclear structures. The nonlinear optical properties of 1 – 3 were investigated.