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Reaction of complex (ArN)Mo(H)(Cl)(PMe3)3 (1) with BPh3 and silane H3SiPh affords a new silyl complex (ArN)Mo(SiH2Ph)(Cl)(PMe3)2 (3) that catalyses facile H–H/Si–H exchange. EXSY experiments suggest that this exchange does not involve the classical pathways such as oxidative addition of hydrogen or silane to the complex or σ-bond metathesis. It is suggested that the exchange may occur in an FLP cage comprised by the complex and the silane.

The iron(ii) salt [Fe(bpp)2](isonicNO)2·HisonicNO·5H2O (1) (bpp = 2,6-bis(pyrazol-3-yl)pyridine; isonicNO = isonicotinate N-oxide anion) undergoes a partial spin crossover (SCO) with symmetry breaking at T1 = 167 K to a mixed-spin phase (50% high-spin (HS), 50% low-spin (LS)) that is metastable below T2 = 116 K. Annealing the compound at lower temperatures results in a 100% LS phase that differs from the initial HS phase in the formation of a hydrogen bond (HB) between two water molecules (O4W and O5W) of crystallisation. Neutron crystallography experiments have also evidenced a proton displacement inside a short strong hydrogen bond (SSHB) between two isonicNO anions. Both phenomena can also be detected in the mixed-spin phase. 1 undergoes a light-induced excited-state spin trapping (LIESST) of the 100% HS phase, with breaking of the O4W⋯O5W HB and the onset of proton static disorder in the SSHB, indicating the presence of a light-induced activation energy barrier for proton motion. This excited state shows a stepped relaxation at T1(LIESST) = 68 K and T2(LIESST) = 76 K. Photocrystallography measurements after the first relaxation step reveal a single Fe site with an intermediate geometry, resulting from the random distribution of the HS and LS sites throughout the lattice., A proton migration across a short strong hydrogen bond can be triggered by spin crossover of a remote Fe2+ cation, with the onset of a photoinduced activation energy barrier for proton motion at low temperatures.

The crystal structure of the radical ferromagnet 1a at 2 K reveals a contraction in the unit cell c constant which, at the molecular level, translates into a decrease in slippage of the radical π-stacks and an increase in ferromagnetic exchange interactions along the stacking axis. The results of BS-DFT calculations using long-range corrected functionals are consistent with an overall ferromagnetic topology.

The spin-crossover behaviour of [Fe(abpt)2(NCS)2] (abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) polymorphs B and D have been studied using single crystal X-ray diffraction to monitor changes in structural features. High pressure single crystal measurements on polymorph B showed that it underwent a monoclinic P21/n (Z’ = 0.5) to triclinic P-1 (Z’ = 2 x 0.5) phase transition between 11.5-13.5 kbar. At which point, it also starts to undergo a thermally inaccessible spin crossover. In polymorph D which also crystallises in the mononclinic space group P21/n (Z’ = 2 x 0.5) one of the unique Fe centres undergoes a thermal spin transition. It also displays light-induced excited spin-state trapping (LIESST), and a structure has been obtained at 30 K through continuous irradiation with a 670 nm 5 mW CW laser. In addition high pressure single crystal measurements on polymorph D showed a stepped pressure induced spin transition. At ~9.6 kbar one of the unique Fe centres had undergone a spin transition and by ~15 kbar both of the unique Fe centres are shown to be essentially low spin, a situation that is thermally inaccessible. Crystallographic data were collected for both polymorphs using variable temperature or high pressure single crystal X-ray diffraction to allow changes in cell parameters, bond lengths and distortion parameters to be monitored for the spin crossover or phase transitions.

Quaternary 4-(2-naphthyl)pyridinium salts with various N-substituents were synthesized. The structure of these salts was determined by X-ray crystallography. The self-assembly of the salts with cavitand molecules – β- and γ-cyclodextrins and cucurbit[7,8]urils – in aqueous solutions was studied by electronic spectroscopy and 1H NMR spectroscopy, including spectrophotometric, fluorescence, and 1H NMR titrations. The formation of inclusion complexes of different stoichiometry and stability, was observed, depending on the structure of N-substituent in the quaternary salt and the cavitand nature and cavity size. The complex formation with cucurbiturils results in considerable changes in the absorption and fluorescence spectra of naphthylpyridine derivatives. Motion of the guest molecules in the cavitand cavities was detected. The X-ray diffraction study was carried out for two polymorphs of 2 : 1 complexes formed by betaine type naphthylpyridine and cucurbit[8]uril, in which the cavitand was located either above the naphthalene residues of a dimeric pair of guest molecules or above the centers of their conjugated moieties.

The spin crossover salt [Fe(bpp) 2 ](isonicNO) 2 ·2.4H 2 O ( 1 ·2.4H 2 O) (bpp = 2,6‐bis(pyrazol‐3‐yl)pyridine; isonicNO = isonicotinate N‐oxide anion) exhibits a very abrupt spin crossover at T 1 /2 = 274.4 K. This triggers a supramolecular linkage (H‐bond) isomerization that responds reversibly towards light irradiation or temperature change. Isotopic effects in the thermomagnetic behaviour reveal the importance of hydrogen bonds in defining the magnetic state. Further, the title compound can be reversibly dehydrated to afford 1 , a material that also exhibits spin crossover coupled to H‐bond isomerization, leading to strong kinetic effects in the thermomagnetic properties.

The physicochemical properties of highly stable supramolecular donor–acceptor (D–A) complexes of a bis(18-crown-6)azobenzene (weak π-donor) with a series of bis(ammonioalkyl) derivatives of viologen-like molecules (π-acceptors) in acetonitrile were studied using cyclic voltammetry, UV–vis absorption spectroscopy, 1H NMR spectroscopy, and density functional theory (DFT) calculations. The crystalline structures of the bis(crown)azobenzene and its complex with a bis(ammoniopropyl) derivative of 2,7-diazapyrene were determined by X-ray diffraction analysis. In solution, all of the supramolecular D–A complexes studied have a pseudocyclic structure owing to ditopic coordination of the ammonium groups of the acceptor to the crown ether moieties of the donor. These complexes show somewhat lower stability as compared with the previously studied complexes of the related derivative of stilbene (strong π-donor), which is explained by the relatively weak intermolecular charge-transfer (CT) interactions. Time-dependent DFT calculations predict that the low-energy CT transition in the D–A complex of the bis(crown)azobenzene with a bis(ammoniopropyl) derivative of 4,4′-bipyridine lies between the local ππ* and nπ* transitions of the azobenzene. The absorption band associated with the CT transition is indiscernible in the spectrum since it is overlapped with broad and more intense ππ* and nπ* bands. It was found that the E → Z photoisomerization quantum yield of the bis(crown)azobenzene decreases by almost an order of magnitude upon the complexation with the 4,4′-bipyridine derivative. This effect was tentatively attributed to the intermolecular electron transfer that occurs in the 1ππ* excited state of the azobenzene and competes with the 1ππ* → 1nπ* internal conversion.

Alternative (‘repeat’) determinations of organic crystal structures deposited in the Cambridge Structural Database are analysed to characterise the nature and magnitude of the differences between structure solutions obtained by diffraction methods. Of the 3132 structure pairs considered, over 20% exhibited local structural differences exceeding 0.25 Å. In most cases (about 83%), structural optimisation using density functional theory (DFT) resolved the differences. Many of the cases where distinct and chemically significant structural differences remained after optimisation involved differently positioned hydroxyl groups, with obvious implications for the correct description of hydrogen bonding. 1H and 13C chemical shifts from solid-state NMR experiments are proposed as an independent methodology in cases where DFT optimisation fails to resolve discrepancies., DFT optimisation often resolves conflicting crystal structure determinations, with NMR shifts helping in cases where optimisation diverges to different structures.

The ethylene dimerization performance of a range of bis(imido)tungsten pre-catalysts, after activation with aluminum co-catalysts, has been assessed. The best performing system achieved an activity of 409,410 (mol C2H4)(mol W)–1h–1 [79.6 wt% 1-butene] with a 1-butene selectivity of 82.4 wt% [290,770 (mol C2H4)(mol W)–1h–1 activity]. In addition to selected previously reported variants, the symmetrical bis(imido)tungsten(VI) complexes [WCl2(NPh)2(tmeda)] (3) and [WCl2(NR)2(dme)] [R = 2,4,6-trifluorophenyl, 7; 2,4,6-triphenylphenyl, 8; 2,4,6-tris(trifluoromethyl)phenyl, 9], were prepared. A series of unsymmetrical bis(imido)tungsten(VI) complexes [WCl2(NDipp)(NR)(dme)] (R = iPr, 11; tBu, 12; 2,4,6-trimethylphenyl, 13; 2,4,6-trichlorophenyl, 14; 2,4,6-trifluorophenyl, 15; 2,6-dinitrophenyl, 16; 2,4,6-triphenylphenyl, 17) were also synthesized using an improved version of a previous preparative route that eases purification. The molecular structures of complexes 5-13 and 15-17 were determined by X-ray crystallographic analysis. Catalysis employing complexes 1-17 unveils a complicated relationship between steric and electronic factors that affects activity and catalyst lifetime, however selectivity is dominated by electronic considerations. Higher reaction temperatures were shown to favor 1-butene selectivity and higher activity, whilst replacement of EtAlCl2 with MeAlCl2 as co-initiator was found to be detrimental. Tungsten(IV) species were demonstrated to be unlikely as the active species during catalysis. Studies of catalysis runs undertaken to varying productivities found that during the nascent phase of reaction a notably lower activity is observed, whilst the selectivity favors C8+ formation during this period, most likely due to activation processes still occurring. The rate of formation of 1-butene was shown to increase with productivity, as a result of the greater solubility of ethylene in the 1-butene generated compared to the chlorobenzene solvent. The formation of C6 by-products was shown to be independent of 1-butene concentrations, consistent with a mechanism whereby 1-butene is only incorporated into secondary products when it reacts prior to dissociation from the tungsten center.

The complex formation of thiamonomethine cyanine dyes bearing two N-ammoniohexyl or two N-ethyl substituents with cucurbit[5,7]urils (CB[5,7]) in aqueous solutions was studied by electronic and 1H NMR spectroscopy, including spectrophotometric, fluorescence, and 1H NMR titration methods. It was found that CB[5] forms external complexes with the dyes, while CB[7] forms internal (inclusion) complexes of 1:1 and 1(dye):2(CB[5,7]) composition. The complexation with CB[5,7] changes the absorption spectra of cyanine dyes and induces a considerable fluorescence enhancement. The stability constants of the complexes were determined (logK1:1 varies in the range from 3.53 to more than 6, and logK1:2 varies in the range from 3.5 to 4.32). The dye with ammoniohexyl substituents forms more stable complexes owing to hydrogen bond formation between the NH3+ groups and the carbonyl groups of the CB[5,7] portals. The structure of supramolecular complexes was confirmed by quantum chemical calculations.

The spin crossover behaviour of [Fe(abpt)2(NCSe)2] (abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) polymorph A has been examined using single crystal X-ray diffraction and variable temperature UV-Vis transmission spectroscopy. The crystal structure of A is reported at sixteen temperatures between 30 and 375 K, all of which are in the monoclinic space group P21/n with Z’ = 0.5. Changes in the crystallographic cell parameters, bond lengths, distortion parameters and intra and intermolecular interactions between 375 K and 30 K are discussed. Continuous irradiation with a 670 nm, 5 mW CW laser at 30 K enabled a light induced excited spin state trapping (LIESST) metastable high spin structure, HS*, to be obtained.

Binding of alkanediammonium ions +H3N(CH2)nNH3+, n = 2–6, to (E)-bis(18-crown-6)stilbene initiates the [2 + 2] photocycloaddition reaction leading mainly to the rctt isomer of 1,2,3,4-tetrakis(benzo-18-crown-6)cyclobutane. The high efficiency and stereoselectivity of this photoreaction in dilute solution are due to the formation of bis-pseudosandwich complexes consisting of two stilbene molecules and two alkanediammonium ions. With a decrease in the length of the polymethylene spacers in the 2:2 complex, the quantum yield of supramolecular [2 + 2] photocycloaddition increases from 0.02 to 0.27, while the quantum yield of the competing E–Z photoisomerization decreases from 0.12 to 0.06. Spectrophotometric observations and density functional theory calculations revealed that (Z)-bis(18-crown-6)stilbene, unlike the E isomer, is able to form pseudocyclic 1:1 complexes with +H3N(CH2)nNH3+, n = 2–6, owing to the proximity of two crown ether moieties. The peculiar spectral properties of these complexes are associated with large torsion angles around the ethylene–benzocrown single bonds. X-ray diffraction analysis showed that co-crystallization of (E)-bis(18-crown-6)stilbene with 1,6-hexanediammonium diperchlorate affords a linear polymer in which the alternating stilbene molecules and diammonium ions are connected by hydrogen bonds.

Liquid crystal n-(alkyloxybenzilidene)-n'-toluidines R−O−C6H4−CH = N−C6H4−CH3 (R = C9H20 1 and C10H21 2) have been investigated by single crystal X-ray structural analysis. The investigation of 2 h...

A series of cross-conjugated dienones was synthesized to study the dependence of physicochemical characteristics on the nature of substituents in the aromatic groups of symmetric cyclopentanone dibenzylidene derivatives. The structure of compounds was established by electronic, IR, and NMR spectroscopy and X-ray diffraction study. All the compounds obtained possess the E,E-geometry. In the crystalline state, the arrangement of the dienone molecules is unfavorable for the intermolecular [2+2] photocycloaddition to take place. The low-temperature phases transition for unsubstituted diphenyl derivative of cyclopentanone was detected using variable-temperature X-ray diffraction and differential scanning calorimetry. Oxidation and reduction potentials of the dienones were measured by cyclic voltammetry. Their dependence on the nature and placement of substituents in the benzene rings was demonstrated. A linear correlation (R = 0.9343) between the difference of electrochemical oxidation and reduction potentials and the energy of the long-wavelength absorption maximum was found, that allows us to recommend the use of the data obtained in the correlation analysis of other compounds of this class.

Polymorphism in racemic pharmaceutical compounds is relatively unexplored. However, this phenomenon may provide an additional tool to crystal engineering, opening the doors to rational design of chiral resolution, chiral enrichment, and chiral purification of pharmaceutical compounds. In this work we report two racemic polymorphs occurring for the nitrate salt of the antidepressant drug fluoxetine (FLX): a racemate (P21/n, Z = 4, Z′ = 1) and a kryptoracemate (Pca21, Z = 4, Z′ = 2). The relative stability of these polymorphs was established through a combination of techniques, namely, differential scanning calorimetric (DSC), thermogravimetric analysis (TGA), hot stage microscopy (HSM), and solubility measurements. Though the two polymorphs share some structural features, the N+–H···O– hydrogen bonds have created dissimilar racemic motifs in their packing, resulting in different enantiomer orientations. The racemate is more stable over the temperature ranges we studied and is monotropically related to kryp...

New 4-pyridine-derived styryl dyes having an ammonioalkyl N-substituent in the pyridine moiety and various substituents in the benzene moiety were synthesized. The formation of pseudodimeric complexes of ammonioalkyl styryl dye derivatives with 18-crown-6-containing styryl dyes of the 4-pyridine, 4-quinoline, and 2-benzothiazole series was studied by 1H NMR in MeCN-d3. It was found that the stability of supramolecular complexes is mainly determined by the monotopic interaction of the ammonioalkyl group with the crown ether moiety via hydrogen bonding. The components of pseudodimeric complexes undergo stereospecific cross-[2+2] photocycloaddition reaction to give unsymmetrical rctt isomers of cyclobutane derivatives owing to the syn-head-to-tail arrangement of components in the initial complex. The efficiency of photoreaction is affected by the N-substituent length, the nature of the substituent in the benzene ring of the ammonioalkyl component, and the nature of the heterocyclic residue of the crown-containing component. The structures of dyes, pseudodimeric complexes, and the cyclobutane derivative were studied by X-ray diffraction.

Hydrogen bonding from a urea group to hydrogen bond acceptor anions can adopt either R_2^1 (6) or R_2^2 (8) motifs depending on the proximity of hydrogen bond acceptor atoms. However, for the sterically bulky and weaker hydrogen bond acceptor triflate anion, hydrogen bond acceptor polymorphism is observed

New styryl dyes of the 2-benzoselenazole series which contain iodide, triiodide, and tosylate anions were synthesized. Crystals of these compounds were grown in different crystal forms – solvent free and hydroquinone, benzene or ethyl acetate solvated ones. X-ray structural studies of the crystals shows that those containing tosylate and triiodide anions form the centrosymmetrically related stacking motif, typical for styryl dye cations and favorable for [2 + 2] photocycloaddition (PCA) reactions. This reaction takes place in crystals with tosylate anions as a single crystal-to-single crystal process. On the contrary, in the triiodide dye crystals, the PCA reaction is lacking, probably due to a weak directional interaction of the selenium atoms with the anions. The iodide dye crystals demonstrate non-typical packing for styryl dyes and manifest as a two-dimensional close packing motif of the cations which is unfavorable for cycloaddition.

In combination with EtAlCl2, complexes {[WCl3(μ-Cl)(N-2,6-iPr2C6H3)]2}, [WCl4(NR)(thf)] (R = Et, iPr, cHx, Ph, 2,6-iPr2C6H3, 4-F-C6H4, and 2,4,6-F3-C6H2), and [WCl2(NR′)(PMe3)3] (R′ = Ph, 2,6-iPr2C6H3) were all productive ethylene dimerization pre-catalysts, giving turnover numbers (TONs) in the range of 400–144 000 (mol C2H4)(mol W)−1 and moderate selectivities toward 1-butene (>66%) depending on the nature of the imido substituent. The formation of C6 side-products resulted from the incorporation of 1-butene rather than direct trimerization, something that is independent of butene concentration. Stoichiometric reactions between the tungsten mono(imido) complexes and alkylaluminum reagents are described, which are consistent with the reduction of the tungsten centre playing an important part in the initiation process. Testing discrete WV and WIV mono(imido) complexes for olefin dimerization revealed the former to be significantly more active, which offers insight into the mode of action of the commercially relevant tungsten mono(imido)-selective dimerization initiators described herein.

Hirshfeld atom refinement (HAR) is a novel X-ray structure refinement technique that employs aspherical atomic scattering factors obtained from stockholder partitioning of a theoretically determined tailor-made static electron density. HAR overcomes many of the known limitations of independent atom modelling (IAM), such as too short element–hydrogen distances, r(X—H), or too large atomic displacement parameters (ADPs). This study probes the accuracy and precision of anisotropic hydrogen and non-hydrogen ADPs and of r(X—H) values obtained from HAR. These quantities are compared and found to agree with those obtained from (i) accurate neutron diffraction data measured at the same temperatures as the X-ray data and (ii) multipole modelling (MM), an established alternative method for interpreting X-ray diffraction data with the help of aspherical atomic scattering factors. Results are presented for three chemically different systems: the aromatic hydrocarbon rubrene (orthorhombic 5,6,11,12-tetraphenyltetracene), a co-crystal of zwitterionic betaine, imidazolium cations and picrate anions (BIPa), and the salt potassium hydrogen oxalate (KHOx). The non-hydrogen HAR-ADPs are as accurate and precise as the MM-ADPs. Both show excellent agreement with the neutron-based values and are superior to IAM-ADPs. The anisotropic hydrogen HAR-ADPs show a somewhat larger deviation from neutron-based values than the hydrogen SHADE-ADPs used in MM. Element–hydrogen bond lengths from HAR are in excellent agreement with those obtained from neutron diffraction experiments, although they are somewhat less precise. The residual density contour maps after HAR show fewer features than those after MM. Calculating the static electron density with the def2-TZVP basis set instead of the simpler def2-SVP one does not improve the refinement results significantly. All HARs were performed within the recently introduced HARt option implemented in the Olex2 program. They are easily launched inside its graphical user interface following a conventional IAM.

1-(3-Ammoniopropyl)-4-[(E)-2-(3,4-dichlorophenyl)vinyl]pyridinium diperchlorate was synthesized and its crystal structure was studied by X-ray diffraction. The photochemical properties of this compound and its complexation with a 18-crown-6-containing derivative of 4-styrylpyridine were studied by electronic spectroscopy. These compounds form a supramolecular complex (logK = 3.89 in MeCN at an ionic strength of 0.01 mol L–1), in which the styryl chromophores are arranged one above another due to stacking interactions. The complexation activates the cross [2+2] photocycloaddition of styrylpyridine derivatives. A procedure is proposed for the global analysis of spectrophotometric data, which takes into account the effect of the ionic strength of the solution on the observed equilibrium reaction.

Phosphinoalkynes P(C≡CC6H4Me-4)Ph2 (1) and P(C≡CC6H4C≡CC6H4Me-4)Ph2 (2) have been prepared from CuI catalysed reactions of the corresponding 1-alkyne and PClPh2. The trimethylamine-N-oxide promoted reaction of PPh3, 1 or 2 with [Fe2(μ-pdt)(CO)6] (pdt = propanedithiolate) affords derivatives [Fe2(μ-pdt)(CO)5{PRPh2}] [R=Ph (3), C≡CC6H4Me (5), C≡CC6H4C≡CC6H4Me (6)] or, at elevated temperatures, [Fe2(μ-pdt)(CO)4(PPh3)2] (4). The cyclic voltammograms of compounds 3 and 4 feature almost fully reversible one-electron oxidation processes and an irreversible reduction, whilst the electrochemical response of the alkynyl phosphine substituted complexes 5 and 6 is irreversible for both oxidation and reduction. IR spectroelectrochemical studies of 4 are consistent with an oxidation processes leading to a delocalized or (Class III) mixed valence [FeFe]3+ core in which the iron centers have an average oxidation state of 1.5. The molecular structures of the alkynyl phosphine substituted clusters 5 and 6 are also reported.

Crystals of molecular complexes of trimethyltrioxane (TMT) with chloroform (CF), bromoform (BF), dichloromethane (DCM), and dibromomethane (DBM) as well as those of pure TMT were grown in situ and characterized by single crystal X-ray crystallography. The CF and BF complexes, as well as those of DCM and DBM, are isostructural. The packing motifs were examined using the vector analysis of pairwise energies of intermolecular interactions. The method shows some deficiencies of the traditional approach based on the analysis of geometrical parameters of short intermolecular contacts.

Crystallization of 2-fluorophenylacetylene at room temperature using high pressure yields three different polymorphs. These have distinct supramolecular assemblies despite the only variation in the crystallization protocol employed being the rate of compression.

A series of 2,5-bis(arylethynyl)rhodacyclopentadienes has been prepared by a rare example of regiospecific reductive coupling of 1,4-(p-R-phenyl)-1,3-butadiynes (R[DOUBLE BOND]H, Me, OMe, SMe, NMe2, CF3, CO2Me, CN, NO2, −C[TRIPLE BOND]C-(p-C6H4[BOND]NHex2), −C[TRIPLE BOND]C[BOND](p-C6H4[BOND]CO2Oct)) at [RhX(PMe3)4] (1) (X=−C[TRIPLE BOND]C[BOND]SiMe3 (a), −C[TRIPLE BOND]C-(p-C6H4[BOND]NMe2) (b), −C[TRIPLE BOND]C[BOND]C[TRIPLE BOND]C[BOND](p-C6H4[BOND]NPh2) (c) or [BOND]C[TRIPLE BOND]C[BOND]{p-C6H4-C[TRIPLE BOND]C[BOND](p-C6H4-N(C6H13)2)} (d) or Me (e)), giving the 2,5-bis(arylethynyl) isomer exclusively. The rhodacyclopentadienes bearing a methyl ligand in the equatorial plane (compound 1 e) have been converted into their chloro analogues by reaction with HCl etherate. The rhodacycles thus obtained are stable to air and moisture in the solid state and the acceptor-substituted compounds are even stable to air and moisture in solution. The photophysical properties of the rhodacyclopentadienes are highly unusual in that they exhibit, exclusively, fluorescence between 500–800 nm from the S1 state, with quantum yields of Φ=0.01–0.18 and short lifetimes (τ=0.45–8.20 ns). The triplet state formation (ΦISC=0.57 for 2 a) is exceptionally slow, occurring on the nanosecond timescale. This is unexpected, because the Rh atom should normally facilitate intersystem crossing within femto- to picoseconds, leading to phosphorescence from the T1 state. This work therefore highlights that in some transition-metal complexes, the heavy atom can play a more subtle role in controlling the photophysical behavior than is commonly appreciated.

A family of styryl dyes of the 4-pyridine series, Et–Py+–CHCH–C6H3(OMe)2 X−, with different anions X−, was synthesized. Their ability to undergo [2 + 2] photocycloaddition (PCA) in the polycrystalline state with the formation of 1,2,3,4-tetrasubstituted rctt cyclobutanes under irradiation with visible light was investigated by 1H NMR spectroscopy. Crystal packing of the dyes and feasibility for the PCA reaction in single crystals were investigated by X-ray structural analysis. Small inorganic anions, such as ClO4−, BF4−, PF6− that do not form secondary interactions with the organic cation, aid the formation of cation stacking motifs of the “head-to-tail” type. In these stacks, any adjacent cations are arranged in an antiparallel fashion and approach one another at distances shorter than 4.2 A, which corresponds to the Schmidt's rule for feasibility of PCA reaction in the solid state. As a result of PCA, rctt isomers of cyclobutane derivatives are formed. Success of the PCA reaction without single crystal degradation was only found for the dye containing BF4− anion. Upon irradiation with UV light of the cyclobutane product formed in the crystal, back phototransformation without single crystal degradation was observed. A number of weak interactions I−⋯H–C in the dye with I− anion prevent significant atomic displacements that accompany the PCA transformation from being achieved. Occurrence of the bulky tosylate anion forming a set of hydrogen bonds with solvate acetonitrile and water molecules aids the formation of “head-to-head” type stacks, with a large separation between the adjacent ethylene bonds. In the dye containing bulky BPh4− anion, the main structure-forming role belongs to anions, which suppress the cation trend to form a stacking packing motif. The dye with picrate anion forms two types of crystals. Crystal packing of one of them excludes any PCA transformation, whereas, the other one permits it, but with single crystal degradation.

New styryl dye of the 2-benzothiazole series was synthesized. The new dye contains two methoxy groups in the benzene ring and tosylate counterion. The [2+2] photocycloaddition (PCA) of the dye was studied in the polycrystalline film and in single crystal. Two modifications of the dye cocrystallizate with hydroquinone differed in the ratio of components were obtained, and their ability to enter PCA was studied. According to the X-ray diffraction data, molecular cations of the dye form stack packings either of syn-“head-to-tail” type or relatively isolated stacking dimers. In all cases, the ethylene bonds of the adjacent cations are brought together and antiparallel, favoring PCA to form the centrosymmetric rctt-isomer of 1,2,3,4-tetrasubstituted cyclobutane. In two cases, the PCA reaction proceeded as the “single crystal-to-single crystal” transformation. Hydrogen bonds in crystals including hydroquinone molecules strengthen the crystal packing retarding the PCA. The back photoreaction (retro-PCA) was detected: it occurs without single crystal decomposition and results in the accumulation of the initial styryl dye in crystal consisting of the cyclobutane derivative. This is the first example of such a transformation in single crystals.

Temperature-dependent regioselectivity between amino and hydroxyl groups mediated by hydrogen bonding was observed in the reaction of acetic anhydride with 2-(2,3-dimethoxyphenyl)- 4-(2-hydroxyphenyl)-2,3-dihydro-1H-1,5-benzodiazepine (1), obtaining 1-acetyl-2-(2,3-dimethoxyphenyl)- 4-(2-hydroxyphenyl)-2,3-dihydro-1H-1,5-benzodiazepine (1a), when these were reacted at room temperature, and 4-(2-acetoxyphenyl)-1-acetyl-2-(2,3-dimethoxyphenyl)-2,3-dihydro-1H-1,5- benzodiazepine (1b), when they were refluxed (148 - 150 °C). Acylation of the less hindered analog 4-(2-hydroxyphenyl)-2-phenyl-2,3-dihydro-1H-1,5-benzodiazepine (2) via crotonyl chloride (a bulky acylating agent compared with acetic anhydride) afforded by refluxing only 1-crotonyl-4- (2-hydroxyphenyl)-2-phenyl-2,3-dihydro-1H-1,5-benzodiazepine (2a). All compounds were characterized spectroscopically, and the molecular structures of compounds 1a and 2a were determined by X-ray diffraction analysis.

The triple decker dinuclear Cr(ii) salt [(η5-C 5Me5)Cr(μ2:η5-P 5)Cr(η5-C5Me5)]+ (SbF6)- has been structurally characterised by multiple temperature X-ray diffraction experiments from 290 K to 12 K. This material shows changes in its structural features which correlate with its magnetic response, including a structural transition with a change of symmetry from the orthorhombic space group Fddd to the monoclinic I2/a at ∼160 K and an abrupt rearrangement of electron density at ∼23 K This journal is © The Royal Society of Chemistry.

The new compounds [M(η-C7H8)L2Cl2](M = Zr, L = PMe31; M = Hf, L = PMe32; M = Zr, L = PMe2Ph 3; M = Hf, L = PMe2Ph 4; M = Zr, L = PMePh25) have been synthesised by reduction of MCl4 using sodium amalgam in the presence of the tertiary phosphine and cycloheptatriene. Lithium indenide reacts with the triene compounds to give [M(η-C7H7)(η5-C9H7)](M = Zr 6 or Hf 8) which react with trimethylphosphine or 1,2-bis(dimethylphosphino)ethane (dmpe) to form [M(η-C7H7)(η5-C9H7)(PMe3)](M = Zr 7 or Hf 9) and [{Hf(η-C7H7)(η5-C9H7)}2(µ-dmpe)]10 respectively. Treatment of 1 or 2 with sodium cyclopentadienide gives [M(η-C5H5)2{η2-1,2-(or -3,4-) C7H8}(PMe3)][M = Zr 11 or Hf 12). The X-ray crystal structures of 1, 10 and [Zr(η-C5H5)2(η2-3,4-C7H8)(PMe3)]11a have been determined.

A 3D hybrid zinc formate framework, [NH(4)][Zn(HCOO)(3)], possessing an acs topology, shows a high degree of mechanical anisotropy and negative linear compressibility (NLC) along its c axis. High-pressure single-crystal X-ray diffraction studies and density functional theory calculations indicate that contraction of the Zn-O bonds and tilting of the formate ligands with increasing pressure induce changes in structure that result in shrinkage of the a and b axes and the NLC effect along c.

Three polymorphs of pyrene-2,7-bis(Bpin)2 (1) and two of pyrene-2-(Bpin) (2), where Bpin = 4,4,5,5-tetramethyl-[1,3,2]dioxaborolane, two different 1:1 co-crystals of 1 with toluene, and co-crystals of hexafluorobenzene (HFB) with 1 (of highly unusual 2:1 composition) and 2 (of usual 1:1 composition) were isolated, studied by X-ray diffraction and differential scanning calorimetry, and described using Hirshfeld surfaces and two-dimensional fingerprint plots. Centrosymmetric phases β- and γ-1 have densities respectively lower and higher than the chiral α-1; α- and β-2 have different packing modes, both with Z′ = 3. Compound 1 is prone to form channel host–guest structures, for example, α- and β-1·PhMe and 1·2HFB. The drastically different stabilities of α- and β-1·PhMe are discussed. The complex 2·HFB has a mixed-stack packing motif. The structural versatility of 1 and 2 is explained by synthon frustration between structurally incongruent pyrene and Bpin moieties.

The reaction of [Co2(CO)6(dppm)] (1) with the ethynyl substituted triarylamines [N(C6H4-4-C≡CSiMe3)(C6H4Me-4)2] (2) or [N(C6H4-4-C≡CSiMe3)2(C6H4Me-4)] (3) affords [{Co2(CO)4(dppm)}{μ-(Me3SiC2-4-C6H4)N(C6H4Me-4)2}] (4) or a mixture of [Co2{μ-Me3SiC2-4-C6H4N(C6H4-4-C≡CSiMe3)(C6H4Me-4)}(CO)4(dppm)] (5) and [{Co2(CO)4(dppm)}2{μ-(Me3SiC2-4-C6H4)2N(C6H4Me-4)}] (6), respectively. A combination of electrochemical measurements in different electrolytes, and IR and NIR spectroscopic studies of these compounds, which feature both organometallic and organic redox active groups, indicates that the cluster centres are oxidised at significantly less positive potentials than the triarylamine moieties. Reaction of 6 with one or two equivalents of [Fe(η-C5H4COMe)Cp]PF6 gives [6][PF6]n (n = 1, 2), which are best described in terms of cluster-localised oxidation processes. Despite the presence of the substantial differences in the first and second cluster based oxidations in 6 (up to 220 mV in CH2Cl2/0.1 M [NBu4][BAr4F]), there is little ground state delocalisation between the cluster centres through the triarylamine bridge. The stabilisation of [6]+ with respect to disproportionation can be attributed to electrostatic effects.

An efficient synthetic route to 2- and 2,7-substituted pyrenes is described. The regiospecific direct C-H borylation of pyrene with an iridium-based catalyst, prepared in situ by the reaction of [{Ir(μ-OMe)cod}(2)] (cod = 1,5-cyclooctadiene) with 4,4'-di-tert-butyl-2,2'-bipyridine, gives 2,7-bis(Bpin)pyrene (1) and 2-(Bpin)pyrene (2, pin = OCMe(2)CMe(2)O). From 1, by simple derivatization strategies, we synthesized 2,7-bis(R)-pyrenes with R = BF(3)K (3), Br (4), OH (5), B(OH)(2) (6), and OTf (7). Using these nominally nucleophilic and electrophilic derivatives as coupling partners in Suzuki-Miyaura, Sonogashira, and Buchwald-Hartwig cross-coupling reactions, we obtained 2,7-bis(R)-pyrenes with R = (4-CO(2)C(8)H(17))C(6)H(4) (8), Ph (9), C≡CPh (10), C≡C[{4-B(Mes)(2)}C(6)H(4)] (11), C≡CTMS (12), C≡C[(4-NMe(2))C(6)H(4)] (14), C≡CH (15), N(Ph)[(4-OMe)C(6)H(4)] (16), and R = OTf, R' = C≡CTMS (13). Lithiation of 4, followed by reaction with CO(2), yielded pyrene-2,7-dicarboxylic acid (17), whilst borylation of 2-tBu-pyrene gave 2-tBu-7-Bpin-pyrene (18) selectively. By similar routes (including Negishi cross-coupling reactions), monosubstituted 2-R-pyrenes with R = BF(3)K (19), Br (20), OH (21), B(OH)(2) (22), [4-B(Mes)(2)]C(6)H(4) (23), B(Mes)(2) (24), OTf (25), C≡CPh (26), C≡CTMS (27), (4-CO(2)Me)C(6)H(4) (28), C≡CH (29), C(3)H(6)CO(2)Me (30), OC(3)H(6)CO(2)Me (31), C(3)H(6)CO(2)H (32), OC(3)H(6)CO(2)H (33), and O(CH(2))(12)Br (34) were obtained from 2. These derivatives are of synthetic and photophysical interest because they contain donor, acceptor, and conjugated substituents. The crystal structures of compounds 4, 5, 7, 12, 18, 19, 21, 23, 26, and 28-31 have also been obtained from single-crystal X-ray diffraction data, revealing a diversity of packing modes, which are described in the Supporting Information. A detailed discussion of the structures of 1 and 2, their polymorphs, solvates, and co-crystals is reported separately.

Semiquinone-bridged bisdithiazolyls 3 represent a new class of resonance-stabilized neutral radical for use in the design of single-component conductive materials. As such, they display electrochemical cell potentials lower than those of related pyridine-bridged bisdithiazolyls, a finding which heralds a reduced on-site Coulomb repulsion U. Crystallographic characterization of the chloro-substituted derivative 3a and its acetonitrile solvate 3a·MeCN, both of which crystallize in the polar orthorhombic space group Pna2(1), revealed the importance of intermolecular oxygen-to-sulfur (CO···SN) interactions in generating rigid, tightly packed radical π-stacks, including the structural motif found for 3a·MeCN in which radicals in neighboring π-stacks are locked into slipped-ribbon-like arrays. This architecture gives rise to strong intra- and interstack overlap and hence a large electronic bandwidth W. Variable-temperature conductivity measurements on 3a and 3a·MeCN indicated high values of σ(300 K) (10(-3) S cm(-1)) with correspondingly low thermal activation energies E(act), reaching 0.11 eV in the case of 3a·MeCN. Overall, the strong performance of these materials as f = ½ conductors is attributed to a combination of low U and large W. Variable-temperature magnetic susceptibility measurements were performed on both 3a and 3a·MeCN. The unsolvated material 3a orders as a spin-canted antiferromagnet at 8 K, with a canting angle φ = 0.14° and a coercive field H(c) = 80 Oe at 2 K.

New 15(18)-crown-5(6)-containing and model methoxy-substituted 1-hetaryl-2-phenylacetylenes of the 4-pyridine and 2-benzothiazole series were synthesized using the addition of bromine to the ethylene fragment of the corresponding styrylheterocycles followed by dehydrobromination under the action of potassium tert-butoxide. The quaternization of the pyridylphenylacetylenes afforded new acetylenyl dyes. The structures of five synthesized compounds were determined by X-ray diffraction analysis.

Tetrasodium p-sulfonatocalix[4]arene exists as a hydrate with approximately 14 water molecules and has three polymorphic modifications, all of which contain a water molecule in the molecular cavity that is engaged in OH···π interactions. Single-crystal neutron structures are reported for two of these three forms and reveal a "compressed" water molecule with short OH bonds. Partial atomic charges and hardness analysis (PACHA) calculations based on the neutron coordinates give an OH···π interaction energy of 6.9-7.5 kJ mol(-1). The PACHA analysis also reveals the dominance of the charge-assisted hydrogen bonds from the Na(+)-coordinated water molecules. The instability of the crystal towards dehydration can be traced to an uncoordinated lattice water site. The remarkable calixarene-Na(+)-hydrate motif is conserved almost unchanged across all three polymorphs. A single-crystal neutron structure is also reported for pentasodium p-sulfonatocalix[4]arene·12H(2)O, which exhibits an intracavity water molecule that is engaged in both OH···π and OH···O hydrogen bonding. The shorter covalent bond to the hydrogen atom that forms the interaction with the aromatic ring is again apparent.

A series of 4-styrylpyridine hydroperchlorates were synthesized, and the [2+2] autophotocycloaddition (PCA) reaction in their polycrystalline films and single crystals resulting in the centrosymmetric rctt isomers of 1,2,3,4-tetrasubstituted cyclobutanes was investigated. Unlike neutral styrylpyridines, their protonated forms are better preorganized for the solid-state PCA reaction. According to the X-ray diffraction data, the cations of these compounds, like related styryl dyes, are mainly stacked in crystals in a head-to-head or head-to-tail fashion with equal probability. Only in the latter type of stacks, the PCA reaction is feasible as a single-crystal-to-single-crystal transformation. The crystal packing is stabilized by hydrogen bonds between organic cations and perchlorate anions, as well as by other weak directional interactions, for example, by S…S interactions, thus preventing the atomic displacements in the course of PCA. The completion of the PCA reaction in single crystals without their degradation was observed only for 15-crown-5-containing 4-styrylpyridine hydroperchlorate. The crystals of the latter compound are stabilized not by hydrogen bonds between the cations and anions but by N+-H…O(macrocycle) hydrogen bonds resulting in the formation of head-to-tail stacked dimers. In the crystals, these dimers are surrounded by a soft shell formed by rotationally and translationally mobile anions and benzene solvent molecules, as well as by conformationally flexible crown-ether moieties of adjacent dimer pairs. This leads to a decrease in the steric strain that occurs in the crystals in the course of PCA and prevents the degradation of single crystals. The PCA reaction is accompanied by the reduction in the crystal symmetry due to the doubling of the unit cell.

Syntheses, characterization and crystal structures of heterotetranuclear [2 × 1 + 1 × 2] co-crystals [{CuIILZnII(H2O)2}{CuIIL}2](ClO4)2 (1) and [{CuIILCdII(H2O)2(CH3CN)}{CuIIL}2](ClO4)2 (2), dinuclear compound [CuIILHgII(CH2COCH3)](ClO4) (3) and heterotrinuclear [2 × 1 + 1 × 1] co-crystal [{CuIILAgI(H2O)}{CuIIL}](ClO4) (4) derived from N,N′-ethylenebis(3-ethoxysalicylaldimine) (H2L) are reported herein. Compounds 3 and 4 crystallize in the orthorhombic Pbca and monoclinic P21/c systems, respectively, while the space group of compounds 1 and 2 is monoclinic C2/c. The structure of 3 consists of a monophenoxo-bridged CuIIHgII dinuclear core in which the mercury(II) centre is dicoordinated by the bridging phenoxo oxygen atom and the CH2 carbon atom of the mono-deprotonated acetone anion. The coordination environment of HgII in this compound is almost linear. In the CuII2AgI compound 4, one diphenoxo-bridged [CuIILAgI(H2O)]+ cation is co-crystallized with one mononuclear [CuIIL] moieties. On the other hand, the structures of the CuII3MII compounds 1 (M = Zn) and 2 (M = Cd) consist of one diphenoxo-bridged dinuclear CuIIMII unit and two mononuclear [CuIIL] moiety; the composition of the dinuclear unit being [CuIILZnII(H2O)2]2+ and [CuIILCdII(H2O)2(CH3CN)]2+ for 1 and 2, respectively. The AgI (in 4), ZnII (in 1) and CdII (in 2) ions in the diphenoxo-bridged dinuclear cores are tri-, tetra- and heptacoordinated, respectively. The metal ions are coordinated to two bridging phenoxo oxygen atoms, with the silver(I) and zinc(II) centres being additionally coordinated to one and two water molecules, respectively. While in the case of cadmium(II), the additional five coordination positions are occupied by two ethoxy oxygen atoms, two water oxygen atoms and one acetonitrile nitrogen atom. The coordination environment of silver(I) in 4 is pyramidal with a scalene O3 triangle as the base, whereas those of zinc(II) and cadmium(II) in 1 and 2 are distorted tetrahedral and distorted pentagonal bipyramidal, respectively. The coordinated water molecule in 4 and each of the two coordinated water molecules in 1 and 2 are encapsulated into the O4 compartment of a [CuIIL] moiety resulting in the [2 × 1 + 1 × 1] (for 4) or [2 × 1 + 1 × 2] (for 1 and 2) cocrystallization and self-assemblies. Clearly, the encapsulation of the coordinated water molecule(s) is the governing force for the formation of dinuclear-mononuclear co-crystals in 1, 2 and 4. In addition all four compounds 1–4 have π–π stacking interactions which form dimers between pairs of adjacent molecules in the structure of 3 consisting of CuIIHgII dimers, while one-dimensional stacks are formed in the CuII3ZnII (1), CuII3CdII (2) and CuII2AgI (4) complexes. The compositions of the title compounds are compared with the related systems derived from the same ligand. The [2 × 1 + 1 × 1] co-crystal, 4, is a new type of system in terms of the number of components. Again, in spite of the tri-, tetra- and hepta-coordinated nature of the second metal ion in the dinuclear cores, co-crystallization in 1, 2 and 4, respectively, are new observations. The accommodation/coordination of varieties of metal ions by the O4 compartment of H2L has also been highlighted in the present investigation.

The spontaneous and photoinduced protonation of 4-(2-naphthyl)pyridine (1) in solutions and in complexes with β-cyclodextrin (β-CD) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) were studied by absorption and fluorescence spectroscopy. The structure and stability of the complexes (log K = 1.5–2.3) of 1, its protonated form 2, and quaternized derivative, 1-methyl-4-(2-naphthyl)pyridinium perchlorate (3), with β-CD and HP-β-CD were studied by 1H NMR. It was shown that irrespective of the solution pH, compound 1 resides in the cyclodextrin cavity. HP-β-CD better binds the neutral form of 1 than β-CD, while naphthylpyridinium salts have approximately equal binding affinity to both cyclodextrins. The structures of salt 3 and pseudorotaxane complex 1@β-CD were determined by X-ray diffraction analysis. According to spectral data, pKa of 1 in water is 5.12, which promotes protonation of nitrogen both in the ground state and in the excited state. As a consequence, the fluorescence spectrum exhibits only the protonated form with a lifetime of 15 ns. The addition of HP-β-CD to a solution of 1 results in inclusion complex 1@HP-β-CD; simultaneously pKa of 1 decreases to 4.62 and non-protonated form fluorescence (NFF) of 1 with a lifetime of 1.25 ns appears. Thus, the residence of 1 in the HP-β-CD cavity hampers its protonation in the excited state. From comparison of the initial regions of fluorescence of 1 in solution and in the HP-β-CD complex after pulse excitation, a mechanism for appearance of short-lived NFF of 1 was proposed. Quantum chemical simulation of the protonation and complexation of 1 in the presence of water was performed. On the basis of results, reversible photoinduced mechanical motion of 1 in the HP-β-CD cavity was suggested.

The syntheses, characterization and crystal structures of four copper(II)/nickel(II)⋯uranyl(VI) self-assemblies of composition [{NiIIL1}2·{(UVIO2)(NO3)2(H2O)2}] (1), [{CuIIL2}2·{(UVIO2)(NO3)2(H2O)2}]·0.68H2O (2), [{NiIIL2}2·{(UVIO2)(NO3)2(H2O)2}] (3) and [{CuIIL3}·{(UVIO2)(NO3)2(H2O)2}]n (4) are described in this investigation (H2L1, H2L2 and H2L3 are the Schiff base ligands obtained on condensing 3-ethoxysalicylaldehyde with ethylenediamine, o-phenylenediamine and trans-1,2-diaminocyclohexane, respectively). Compounds 1 and 4 crystallized in the monoclinic P21/n and C2/c space groups, respectively, while compounds 2 and 3 crystallized in the triclinic space group P. Two water molecules of the [(UVIO2)(NO3)2(H2O)2] moiety in 1–4, have a linear H2O–U–OH2 arrangement. Each of these two water molecules in 1–3 interacts with the O(phenoxo)2O(ethoxy)2 compartment of a mononuclear copper(II) or nickel(II) moiety due to the formation of bifurcated hydrogen bonds between each of the two water hydrogen atoms and a pair of one phenoxo and one ethoxy oxygen atoms resulting in the interlinking of the two mononuclear 3d units by the [(UVIO2)(NO3)2(H2O)2] synthon and therefore these three compounds may be considered as supramolecular dimers. Compounds 1–3 are also two component [1 × 2 + 1 × 1] co-crystals consisting of two mononuclear copper(II) or nickel(II) units and one [(UVIO2)(NO3)2(H2O)2] moiety. On the other hand, in 4, two water molecules, from two different [(UVIO2)(NO3)2(H2O)2] moieties, interact with one O(phenoxo)2O(ethoxy)2 compartment resulting in the formation of a self-assembled one-dimensional topology. Again, since one mononuclear copper(II) unit and one [(UVIO2)(NO3)2(H2O)2] moiety exist in a single crystal in 4, this compound is a two component [1 × 1 + 1 × 1] co-crystal. The outcomes of the present study utilize [(UVIO2)(NO3)2(H2O)2] synthon to derive 3d⋯5f co-crystals, provide the first observation of the interaction of two water molecules with one O(phenoxo)2O(ethoxy)2 compartment, demonstrate the formation of supramolecular dimers and show the first example of a one-dimensional self-assembly resulting from water⋯O4 compartment hydrogen bonds, and the first example of [1 × 2 + 1 × 1] co-crystals in 3-ethoxysalicylaldehyde-diamine ligand system.

Reactions of 1-(2,4-dinitrophenyl)pyridinium chloride and 2-(2,4-dinitrophenyl)isoquinolinium chloride with 2,3-dimethylbenzothiazolium iodide in hot pyridine allows introduction of an aryl residue into the thiazole ring via intermolecular transformation of the pyridine ring of Zincke’s salts with participation of the methyl group in position 2 of the benzothiazolium salt.

International audience; Reaction of [PdMe2(tmeda)] with pyridyl-N-di(tert-butyl)phosphinoimine spontaneously affords an unusual bimetallic palladium(I) ligand-based biradical complex, which behaves as a "masked" form of Pd0 in its reactions with neutral ligands and chlorobenzene.

A number of N-alkylnitrobenzoaza-15-crown-5 with the macrocycle N atom conjugated with the benzene ring were obtained. The structural and complexing properties of these compounds were compared with those of model nitrobenzo- and N-(4-nitrophenyl)aza-15-crown-5 using X-ray diffraction, 1H NMR spectroscopy, and DFT calculations. The macrocyclic N atom of benzoazacrown ethers are characterized by a considerable contribution of the sp3-hybridized state and a pronounced pyramidal geometry; the crownlike conformation of the macrocycle is preorganized for cation binding, which facilitates complexation. The stability constants of the complexes of crown ethers with the NH4 +, EtNH3 +, Na+, K+, Ca2+, and Ba2+ ions were determined by 1H NMR titration in MeCN-d3. The most stable complexes were obtained with alkaline-earth metal cations, which is due to the higher charge density at these cations. The characteristics of the complexing ability of N-alkylnitrobenzoaza-15-crown-5 toward alkaline earth metal cations are comparable with analogous characteristics of nitrobenzo-15-crown-5 and are much better than those of N-(4-nitrophenyl)aza-15-crown-5.

Novel 15-hydroxybenzomonothia-15-crown-5 containing the sulfur atom linked with the benzene ring and its S-oxide were synthesized. The stability constants for the complexes of the obtained benzocrown ethers and a reference 15-hydroxybenzo-15-crown-5 with Na, Ca, AgI, Cd, HgII, and PbII perchlorates were determined by 1H NMR titration. In MeCN-d3, the benzothiacrown ether demonstrates a high selectivity towards the thio- and oxothiophilic Hg2+ (logK 1 = 7.1) and Pb2+ ions (logK 1 = 7.4). In MeCN-d3-D2O mixtures, the stabilities of the most of complexes decrease sharply due to competitive hydration of the metal cations except for the “soft” Ag+ and Hg2+ ions having low affinity for the “hard” oxygen atoms and, on the contrary, very high affinity for the “soft” SII atoms. This results in the change in selectivity of complexation: at the water content in solution of 20%, the benzothiacrown ether binds preferably the Hg2+ (logK 1 = 5.0) and Ag+ ions (logK 1 = 2.7). In MeCN-d3, the benzothiacrown-derived sulfoxide is a weak and non-selective complexing agent towards all the metal cations under study; the reference 15-hydroxybenzo-15-crown-5 forms more stable complexes with the oxophilic sodium, calcium, and lead(ii) cations. The conformational features of the benzocrown ethers and their metal complexes established by NMR spectroscopy and X-ray diffraction are discussed. The found characteristics of the complexing ability of benzomonothia-15-crown-5 where the sulfur atom is in conjugation with the benzene ring reveal that the macrocyclic ligands with such a structure are promising as high-selective and efficient complexing agents for the “soft” mercury(ii) and silver(i) cations in acetonitrile-water mixtures.

Photophysikalische Untersuchungen ergaben fur eine Reihe von Rhodiumkomplexen unerwartet hohe Fluoreszenzquantenausbeuten (Φf bis 69 %, τf≈1–3 ns) und ein unerwartet langsames Intersystem-Crossing. Diese neue Verbindungsklasse hinterfragt das gangige Modell zum Verhalten angeregter elektronischer Zustande und zur Rolle von Schweratomen in Intersystem-Crossing-Prozessen. THF=Tetrahydrofuran, Tol=Toluol.

The crystals of five new low-melting co-crystals of chloroform with organic solvents had been grown in situ and their crystal structures were determined by single-crystal X-ray crystallography. Various aspects of the molecular packing and the role of Cl⋯Cl interactions in these compounds are discussed.

The crystal structures of six new partially fluorinated aryl 1,2,3,5-dithiadiazolyls [ArCNSSN]˙ are reported [Ar = 2,6-F2C6H3 (4); Ar = 3,4-F2C6H3 (5); Ar = 3,5-F2C6H3 (6); Ar = 2,3,6-F3C6H2 (9); Ar = 2,4,6-F3C6H2 (11); and Ar = 3,4,5-F3C6H2 (12)] and compared with three previously reported structures in this series (Ar = 2,3-F2C6H3 (1); Ar = 2,5-F2C6H3 (3); Ar = 2,3,4-F3C6H2 (7)]. Radical 4 is shown to be polymorphic. Molecular electrostatic potential maps have been used to rationalise these structures. These reveal that whilst single F atoms appear to have little structure-directing influence, combinations of an ortho-F on the phenyl ring and a heterocyclic ring N, or several F atoms located in mutually ortho positions with respect to each other, generate significant regions of negative charge which have a substantial structure-directing influence.

Syntheses, characterization and structures of heterodinuclear compound [CuIIL1BiIII(NO3)3] (1), sandwich type heterotrinuclear compound [(CuIIL1)2BaII(NO3)2]·0.2H2O (2), heterotetranuclear compound [{CuIIL1PbII(µ-NO3)(NO3)}2] (3) and heterohexanuclear [2 × 1 + 1 × 4] cocrystal [(UVIO2)2(µ-H2O)2(NO3)4]·4[CuIIL1⊂(H2O)] (4) are described in this investigation (H2L1 = N,N′-ethylenebis(3-ethoxysalicylaldiimine)). Compounds 1 and 4 crystallize in orthorhombic P212121 and triclinic Pī systems, respectively, while the space group of compounds 2 and 3 is monoclinic P21/c. The structure of 1 consists of a diphenoxo-bridged CuIIBiIII dinuclear core containing three chelating nitrates and a 10-coordinate bismuth(III) centre. The dinuclear cores are self-assembled to two dimensions through intermolecular nitrate oxygen⋯copper(II) semicoordination and weak C–H⋯O hydrogen bonds. Compound 2 is a double-decker CuIIBaIICuII system in which a barium(II) ion is sandwiched between two mononuclear [CuIIL1] moieties. The barium(II) centre is 11-coordinate, four phenoxo and four ethoxy oxygen atoms and one chelating and one monodentate nitrate ions. Compound 3 is a tetranuclear system (dimer of two dinuclear moieties) in which one nitrate is chelating, while the second nitrate behaves as both a chelating and bridging ligand. The lead(II) centre is 9-coordinate in this compound. Compound 4 is a [2 × 1 + 1 × 4] cocrystal of one diaqua-bridged diuranyl(VI) moiety, containing two chelating nitrates and 8-coordinated hexagonal bipyramidal uranium(VI) centres and four inclusion species [CuIIL1⊂(H2O)]. The governing factor for the self-assembled cocrystallization in 4 are the C–H⋯·π and C–H⋯O hydrogen bonds. The compounds reported in this investigation and other heteronuclear systems derived from N,N′-ethylenebis(3-ethoxysalicylaldiimine) indicate that this ligand system is an important example which gives rise to structurally diverse heteronuclear compounds. In addition to the structural diversity, the structural resemblance of bismuth(III) with lanthanides(III) and utilization of noncovalent interactions to form self-assembly and cocrystals are the major outcomes of the present investigations.

A simple N,N′-diaryl urea derivative was found to form four different anhydrous crystal forms (I−IV°), which can be crystallized in pure form by several techniques from solution as well as from the melt. These polymorphs were characterized by thermomicroscopy, differential scanning calorimetry, Fourier-transform infrared spectroscopy and single crystal and powder X-ray diffraction. The polymorphs were found to be purely monotropically related with large differences in their heats of fusion (11.1 kJ mol−1 for the least stable form I, 34.5 kJ mol−1 for the most stable form IV°). The crystal structures of all forms show the same conformer for forms I−III and a second conformer in form IV°. However, the hydrogen bonding motifs in all of the polymorphs are the same and thus the compound can be seen as a model for the importance of the entire crystal packing arrangement to the overall energy and stability of the crystal form, as opposed to just a few dominant interactions.