C—H⋯O,C—H⋯π and π–π inter­actions in three benzofuran‐2‐yl ketone derivatives

The mol­ecules of 2‐benzoyl‐1‐benzofuran, C₁₅H₁₀O₂, (I), inter­act through double C—H⋯O hydrogen bonds, forming dimers that are further linked by C—H⋯O, C—H⋯π and π–π inter­actions, resulting in a three‐dimensional supramolecular network. The dihedral angle between the benzo­yl and benzofuran fragments in (I) is 46.15 (3)°. The mol­ecules of bis­(5‐bromo‐1‐benzofuran‐2‐yl) ketone, C₁₇H₈Br₂O₃, (II), exhibit C₂ symmetry, with the carbon­yl group (C=O) lying along the twofold rotation axis, and are linked by a combination of C—H⋯O and C—H⋯π inter­actions and Br⋯Br contacts to form sheets. The stability of the mol­ecular packing in 3‐mesit­yl‐3‐methyl­cyclo­but­yl 3‐methyl­naphtho[1,2‐b]furan‐2‐yl ketone, C₂₈H₂₈O₂, (III), arises from C—H⋯π and π–π stacking inter­actions. The fused naphthofuran moiety in (III) is essentially planar and makes a dihedral angle of 81.61 (3)° with the mean plane of the trimethyl­benzene ring.     

The first metal complex of p-nitrobenzoxasulfamate. Synthesis, spectral and structural characterization of triaquabis(p-nitrobenzoxasulfamato)copper(II) monohydrate

The local structure of molten LaCl₃ was investigated by X-ray absorption fine structure of the La K-edge. The nearest La³⁺-Cl⁻ distance and coordination number were 2.89±0.01 Å and 7.4±0.5 from the curve fitting of the first peak in the Fourier transform magnitude |FT|. The coordination number larger than 6 suggests that the local structure of molten LaCl₃ is not a simple octahedral coordination (LaCl₆)³⁻, but 7-fold (LaCl₇)⁴⁻ and/or 8-fold (LaCl₈)⁵⁻ complexes. The first La³⁺-La³⁺ distance, of which correlation was observed as a weak second peak in the |FT|, was evaluated to be 4.9 Å. It suggests that the distorted corner-sharing connection of the complex species is predominant in the melt, in contrast with molten YCl₃ in which the edge-sharing connection of the 6-fold (YCl₆)³⁻ mainly exists.     

Bis(pyridine‐2,6‐dimethanol‐N,O,O′)cobalt(II) and ‐copper(II) disacchar­inate dihydrate: three‐dimensional structures with extensive hydrogen bonds and aromatic π–π‐stacking interactions

Bis­(pyridine‐2,6‐di­methanol‐N,O,O′)­cobalt(II) disaccharinate dihydrate, [Co(C₇H₉NO₂)₂](C₇H₄NO₃S)₂·2H₂O, (I), and bis­(pyridine‐2,6‐di­methanol‐N,O,O′)copper(II) disaccharinate dihydrate, [Cu(C₇H₉NO₂)₂](C₇H₄NO₃S)₂·2H₂O, (II), collectively [M(dmpy)₂](sac)₂·2H₂O (where M is Co^II or Cu^II, sac is the saccharinate anion and dmpy is pyridine‐2,6‐di­methanol), are isostructural. The [M(dmpy)₂]²⁺ cations exhibit distorted octahedral geometry in which the two neutral dmpy species act as tripodal N,O,O′‐tridentate ligands. The crystal packing is determined by hydrogen bonding, as well as by weak pyridine–saccharinate π–π‐stacking interactions.     

The first tris(saccharinato) complexes. Syntheses, spectral, thermal and structural characterization of ApyH[Cu(N–sac)2(O–sac)(H2O)2] and ApyH[Zn(N–sac)3- (H2O)] (ApyH=2–aminopyridinium and sac=saccharinate)

The reaction of the Schiff base salicylideneaminopyridine with [M(sac)₂(H₂O)₄] · 2H₂O, where M is copper(II) or zinc(II), and sac is the saccharinate anion, results in the formation of the new tris(saccharinato) complexes ApyH[Cu(N-sac)₂ (O-sac)(H₂O)₂] (1) and ApyH[Zn(N-sac)₃(H₂O)] (2), which have been characterized by elemental analyses, magnetic measurements, FT-IR spectroscopy, thermal analysis and X-ray diffraction. The Schiff base did not coordinate to the metal ions, but decomposed during the reaction, forming a 2-aminopyridinium cation ApyH, which remained outside the coordination sphere as a counter ion. (1) and (2) are the first examples of mononuclear tris(saccharinato) complexes of copper(II) and zinc(II). Both complexes are isomorphous with the triclinic space group P-1, (1) consisting of an ApyH cation and a [Cu(sac)₃(H₂O)₂]^– anion in which the copper(II) ion has trigonal bipyramidal surroundings. The sac ligands in (1) exhibit unusual and non-equivalent coordination, behaving as ambidentate ligands. One of them coordinates to the metals through the carbonyl oxygen atom, while the other two sac ligands are bonded to the metals via the imino nitrogen atom. The zinc(II) ion in (2) is tetrahedrally coordinated by three N-donor sac ligands and an aqua ligand. The crystal structures of (1) and (2) are stabilized by intermolecular hydrogen bonds and aromatic – stacking interactions.     

Copper(II)-saccharinato complexes with piperazine and N-(2-aminoethyl)piperazine ligands

Two copper(II) complexes of the saccharinate anion (sac) with piperazine (ppz) and N-(2-aminoethyl)piperazine (aeppz), namely [Cu(sac)₂(ppz)(H₂O)]_n (1) and trans-[Cu(sac)₂(aeppz)₂] (2), have been synthesized and characterized by elemental analyses, UV–Vis, FT-IR, TGA/DTA, X-ray diffraction and magnetic measurements. The ppz ligands in 1 bridge the copper(II) centers through both nitrogen atoms to form a 1D helical chain structure and the distorted trigonal-bipyramidal coordination geometry at each copper center is completed by an aqua and a pair of N-bonded sac ligands. The helical chains are linked by Ow–H?O hydrogen bonds to build a 2-D network. In complex 2, copper(II) ions are octahedrally coordinated by two sac anions and two neutral aeppz ligands, displaying a distorted octahedral coordination. Sac is O-bonded via the carbonyl group, while ppzea acts as a N,N′-bidentate chelating ligand. The molecules are connected by N–H?N and N–H?O hydrogen bonds, forming a linear chain. In the thermal decomposition of both complexes, the removal of the aqua and ppz or aeppz ligand takes place endothermically in the first stages and the sac moiety undergoes highly exothermic decomposition at higher temperatures to give CuO.     

A novel two-dimensional silver(I) saccharinato coordination polymer constructed from weak Ag?C interactions: Synthesis, IR spectra and X-ray structure

A new dinuclear silver(I)-saccharinato (sac) complex with acetonitrile (MeCN), [Ag₂(sac)₂(MeCN)₂]_n has been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. The silver(I) ions are doubly bridged by two sac ligands, leading to a short argentophilic contact of 2.9074(3) Å. Each silver(I) ion exhibits a square-planar coordination geometry including the Ag-Ag bonds. The individual dimeric molecules are extended into a two-dimensional layered structure by weak Ag?C_sac (η²) interactions of ca. 3.2 Å. These interactions were discussed and compared with those found in the first silver(I)-sac complex [Ag(sac)]_n.     

trans-Bis(ethanolamine-N,O)bis(saccharinato-N)copper(II)

In the title complex, [Cu(C₇H₄NO₃S)₂(C₂H₇NO)₂], the Cu^II centre lies on an inversion centre and exhibits octahedral coordination, with the two ethano­lamine (Hea) and two saccharinate [sac; anionic 1,2-benziso­thia­zol-3(2H)-one 1,1-dioxide] ligands in a trans configuration. The bidentate Hea ligands bridge axial and equatorial positions and the sac anions occupy equatorial sites around the distorted octahedral copper(II) centre [Cu—O = 2.3263 (16), Cu—N_Hea = 1.9923 (16) and Cu—N_sac = 2.1776 (16) Å].     

Heat transfer enhancement in a tube with equilateral triangle cross sectioned coiled wire inserts

The heat transfer and pressure drop were experimentally investigated in a coiled wire inserted tube in turbulent flow regime. The coiled wire has equilateral triangular cross section and was inserted separately from the tube wall. The experiments were carried out with three different pitch ratios (P/D = 1, 2 and 3) and two different ratio of equilateral triangle length side to tube diameter (a/D = 0.0714 and 0.0892) at a distance (s) of 1 mm from the tube wall in the range of Reynolds number from 3500 to 27,000. Uniform heat flux was applied to the external surface of the tube and air was selected as fluid. The experimental results obtained from a smooth tube were compared with those from the studies in literature for validation of experimental set-up. The use of coiled wire inserts leads to a considerable increase in heat transfer and pressure drop over the smooth tube. The Nusselt number rises with the increase of Reynolds number and wire thickness and the decrease of pitch ratio. The highest overall enhancement efficiency of 36.5% is achieved for the wire with a/D = 0.0892 and P/D = 1 at Reynolds number of 3858. Consequently, the experimental results reveal that the best operating regime of all coiled wire inserts is detected at low Reynolds number, leading to more compact heat exchanger.