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The synthesis, structure and catalytic performance of water-soluble Al(iii), Fe(iii) and Cu(ii) formazanates in the oxidation of cyclohexane and cyclohexanol to the coresponding organic products are reported.

Chalcogen bonding as a synthetic tool in metal-mediated synthesis and engineering of the secondary coordination sphere of copper(ii) complexes.

The synthesis, supramolecular packing and intermolecular interactions of Co(ii/iii), Ni(ii) and Cu(ii) carbamimidoyl (imino(1H-pyrazol-1-yl)methyl)amidates are reported, as well as their catalytic activity in the oxidation of styrene to benzaldehyde.

The role of substituents on resonance assisted hydrogen bonding (RAHB) vs. intermolecular hydrogen bonding is highlighted in known arylhydrazones of active methylene compounds (AHAMCs) and in their new representatives – (E/Z)-2-(2-(para-substitutedphenyl)hydrazineylidene)-N,N-diethyl-3-oxobutanamides (–C2H5, –H, –COOH, –CN). The strength of the H-bond depends on the attached functional groups to both the active methylene fragment and the aromatic moiety of the AHAMC. For instance, attachment of the strong electron donor group –N(C2H5)2 (σp = −0.72) to the active methylene fragment of AHAMC allows to isolate this class of compounds without RAHB but with strong intermolecular H-bonds, which are the first examples reported herein.

Advances in large-scale green hydrogen production (LGHP) create commercial opportunities for enhancing rapid offshore wind farm (OWF) development. This study investigates whether LGHP co-location at OWF sites improves those OWF’s economic outlooks under potential electrical grid capacity bottlenecks towards 2050. Eight cases have been studied using measured annual OWF power production series and cost estimation integrated with offshore engineering experience: i) two base cases: 2 GW OWFs with HVAC and HVDC transmission infrastructure showing that the levelized cost of electricity (LCOE) increases, and ii) six LGHP co-location cases demonstrating that the calculated levelized cost of hydrogen (LCOH) reduces when the LGHP capacity increases from 20% to 50%, and 100% of 2 GW. Furthermore, three economic improvement factors studied are: i) utilizing existing gas pipelines reducing LCOH by 7.5%, ii) hydrogen for offshore customers changing “no-go” projects to “go”, and iii) scaling-up from 2 to 4 GW reduced the LCOH by 17%. This study shows that LGHP co-location is effective at maintaining OWF full production, but has higher risks including i) LGHP co-location safety at OWFs, ii) high costs to cover more operational conditions and iii) running LGHP operations using high, fluctuating OWF power. Further R&D of LGHP co-location are recommended.

Two tetranuclear and two mononuclear Cu(II) complexes with arylhydrazones of malononitrile derived ligands (compounds 1–2 and 3–4, respectively), one trinuclear Co(II/III) complex with an arylhydrazone of acetoacetanilide (5) and one tetranuclear Zn(II) complex of 3-(2-carboxyphenyl-hydrazone)pentane-2,4-dione (6) were screened as potential catalysts in the peroxidative oxidation of cyclohexane by aqueous H2O2 in acetonitrile. The best results were attained in the presence of pyrazine-2-carboxylic acid (PCA) with 1 (26% yield, TON = 52.0) and with 2 (24%, TON = 48.0) after 4 h at 40 °C. In the presence of complexes 5 and 6, no oxygenated products were detected in the studied conditions. The employment of non-conventional conditions like supercritical carbon dioxide (scCO2) as reaction medium or microwave (MW) irradiation was assessed for complexes 1 and 2. After 6 h in acetonitrile–scCO2, at 50 °C and with HNO3 as promoter, only 17% yield was achieved using 1 as catalyst, and 21% using 2. Total yields of oxygenates up to 14 (with 1) and 13% (2) and TOFs of 56.0 and 52.0 h−1, respectively, were obtained working under MW irradiation at 70 °C and for the much shorter time of 0.5 h.

Metal complex catalysis, in which coordination compounds are designed as catalysts for chemical transformations employing noncovalent interactions, is emerging as a powerful catalytic method for organic synthesis. One of the main advantages of metal catalysis is that coordination compounds can promote various organic transformations not only by coordination bond but also through noncovalent interactions, such as hydrogen, halogen, chalcogen, pnictogen, tetrel and triel bonds, as well as metal-metal, cation-π, anion-π, lone pair-π, π-π stacking, agostic, pseudo-agostic, anagostic, dispersion-driven, lipophilic, etc., or their cooperation. In recent years, the concept of designing metal complex catalysts with noncovalent bond donor or acceptor sites has emerged as a promising strategy for developing selective catalytic transformations. In this review we discuss several recent relevant examples on the auxiliary/crucial role of noncovalent interactions in functionalization of alkanes, alkenes, alkynes, aromatics, heterocycles, aldehydes, ketones and alcohols catalyzed by metal complexes.

A series of water soluble copper(II) complexes, [Cu(κO1O2N-H2L1)(H2O)2]·2H2O (2), [Cu(κO-H3L1)2(H2O)4] (3), [Cu(κO-H4L2)2(H2O)4] (5) and [Cu(H2O)6]·2H2L3·2(CH3)2NCHO (7), were prepared by the reaction of Cu(NO3)2·3H2O with sodium (Z)-2-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)benzenesulfonate, [Na(μ4-1:2κO1,2κO2,3κO3,4κO4-H3L1)]n (1; for 2 and 3), sodium (Z)-3-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)-4-hydroxybenzene-sulfonate, [Na(μ-1κO1,2κO2-H4L2)]2 (4; for 5) or sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazineyl)naphthalene-1-sulfonate, [Na(μ-1κO1O2,2κO3-H2L3)(CH3OH)2]2 (6; for 7). Compounds 1–7 were fully characterized, also by single-crystal X-ray diffraction analysis, and applied as homogeneous catalysts for the azide–alkyne cycloaddition (AAC) reaction to afford 1,4-disubstituted 1,2,3-triazoles. A structure–catalytic activity relationship has been recognized for the first time on the basis of the occurrence of resonance- and charge-assisted hydrogen bond interactions (RAHB and CAHB), in charge and ligand binding modes, enabling the catalytic activity of the compounds to be ordered as follows: Cu(NO3)2 ≪ 7 (complex salt with RAHB and CAHB) < 3 (with RAHB and CAHB) < 5 (with RAHB) < 2 (neither RAHB nor CAHB). Complex 2, without such non-covalent interactions, was found to be the most efficient catalyst for the AAC reaction, affording up to 98% product yield after being placed for 15 min, at 125 °C, in a water/acetonitrile mixture under low power (10 W) MW irradiation.

Lanthanide complexes have attracted a widespread attention due to their structural diversity, as well as multifunctional and tunable properties. The development of lanthanide based functional materials has often relied on the design of the secondary coordination sphere of the corresponding lanthanide complexes. For instance, usually simple lanthanide salts (solvento complexes) do not catalyze effectively organic reactions or provide low yield of the expected product, whereas the presence of a suitable organic ligand with a noncovalent bond donor or acceptor centre (secondary coordination sphere) modifies the symmetry around the metal centre in lanthanide complexes which then successfully can act as catalysts in both homogenous and heterogenous catalysis. In this minireview, we discuss several relevant examples, based on X-ray crystal structure analyses, in which the hydrogen, halogen, chalcogen, pnictogen, tetrel and rare-earth bonds, as well as cation-π, anion-π, lone pair-π, π-π and pancake interactions, are used as a synthon in the decoration of the secondary coordination sphere of lanthanide complexes.

The purpose of this study is to determine the relationship between grit and parenting style of mother among Indian rural adolescents. Parental Authority Questionnaire [1] and Short Grit Scale [2] was used to meet objectives of the paper. A sample of 60 adolescents was chosen from private institution located at Bathinda (Punjab) by using convenience sampling technique. Results of correlation analysis revealed that significant (negative) relationship exists between mother’s authoritarian parenting style (only) and grit. This is true for both genders and for adolescents who comes from joint families. Educational implication of the study signifies that the suitable informative and counseling sessions should be organised for the parents to make them conscious of the appropriate parenting style for the development of gritty adolescents.

A series of 4,5-dibromo-2-(4-substituted phenyl)hexahydro-3a,6-epoxyisoindol-1(4H)-ones were synthesized by reaction of the corresponding 2-(4-substituted phenyl)-2,3,7,7a-tetrahydro-3a,6-epoxyisoindol-1(6H)-ones with [(Me2NCOMe)2H]Br3 in dry chloroform under reflux for 3−5 h. In contrast to the 4-F and 4-Cl substituents, one of the bromine atoms of the isoindole moiety behaves as a halogen bond donor in the formation of intermolecular halogen bonding in the 4-H, 4-Br and 4-I analogues. Not only intermolecular hydrogen bonds, but also Ha⋯Ha and Ha⋯π types of halogen bonds in the 4-H, 4-Br, and 4-I compounds, contribute to the formation of supramolecular architectures leading to 2D or 3D structures.

Abstract Advances in large-scale green hydrogen production (LGHP) create commercial opportunities for enhancing rapid offshore wind farm (OWF) development. This study investigates whether LGHP co-location at OWF sites improves those OWF’s economic outlooks under potential electrical grid capacity bottlenecks towards 2050. Eight cases have been studied using measured annual OWF power production series and cost estimation integrated with offshore engineering experience: i) two base cases: 2 GW OWFs with HVAC and HVDC transmission infrastructure showing that the levelized cost of electricity (LCOE) increases, and ii) six LGHP co-location cases demonstrating that the calculated levelized cost of hydrogen (LCOH) reduces when the LGHP capacity increases from 20% to 50%, and 100% of 2 GW. Furthermore, three economic improvement factors studied are: i) utilizing existing gas pipelines reducing LCOH by 7.5%, ii) hydrogen for offshore customers changing “no-go” projects to “go”, and iii) scaling-up from 2 to 4 GW reduced the LCOH by 17%. This study shows that LGHP co-location is effective at maintaining OWF full production, but has higher risks including i) LGHP co-location safety at OWFs, ii) high costs to cover more operational conditions and iii) running LGHP operations using high, fluctuating OWF power. Further R&D of LGHP co-location are recommended.

Intramolecular chalcogen bonding in arylhydrazones of sulfamethizole is strengthened by conjugation in the π-system of a noncovalent five-membered ring. The S⋅⋅⋅O distance in the sulfamethizole moiety of these compounds ranges from 2.698(3) to 2.806(15) Å, which indicates its strong dependence on the attached arylhydrazone fragments. Information on the nature of the intramolecular chalcogen bond was afforded by DFT calculations.

The pnictogen bond (PnB) is a noncovalent attraction between electrophilic pnictogen atoms, originated from the anisotropic distribution of electron density on Pn in a molecular entity, and a nucleophilic (Nu) region in the same (intramolecular) or another (intermolecular) molecular entity: R–Pn⋯Nu (Pn = N, P, As, Sb or Bi; R = electron withdrawing atom or group; Nu = Ha, Ch, Pn, π-system, anion, etc.). Like the halogen and chalcogen bonds, PnB is a directional noncovalent interaction with a preference for a linear geometry, R–Pn⋯Nu angle approaching 180°. In contrast to the halogen and chalcogen atoms, the pnictogen atoms are able to introduce three electrophilic centres on the Pn atom (on account of the existence of three species bonded to the pnictogen atom), which gives an additional advantage in the use of these weak forces in coordination chemistry. In this review we highlight several recent relevant examples, based on X-ray crystal structure analyses, in which PnB is used as a synthon in the construction and design of coordination and organometallic compounds.

A series of 2-(4-substituted benzoyl)thiazolo[3,2-a]pyridin-4-ium bromides [−OCH3 (1), –H (2), –F (3), −Cl (4)] was obtained by the heterocyclization reaction of the corresponding 2-bromo-1-(4-substituted phenyl)-3,3-diethoxypropan-1-ones with pyridine-2-thiol in dry isopropyl alcohol under reflux for 2 h. The new compounds 1–4 were characterized by elemental analysis, 1H and 13C NMR spectroscopy and single crystal X-ray diffraction. Both the negative charge-assisted (S⋯Br−) and normal (S···π) chalcogen bonds were found in the crystal packing of 2−4, whereas one of the hydrogen atoms of an electron-donating –OCH3 group in 1, behaves as a bifurcated hydrogen bond donor centre towards a sulfur atom of the thiazolo ring and an oxygen atom of C O group of a neighboring molecule leading to the intermolecular hydrogen bonds. The optical properties of 1−4 in DMSO, DMF and MeOH were investigated by UV–vis absorption spectroscopy, with λmax being dependent on the solvent polarity and attached substituents (−OCH3, –H, –F, −Cl) at the para-position of the aromatic moiety.

Schiff base condensation of 2-nitrobenzaldehyde with (para-substituted phenyl)hydrazine in the presence of CH3COONa in EtOH at 80 °C produces (E)-1-(para-substituted phenyl)-2-(2-nitrobenzylidene)hydrazines [−OCH3 (1), −CH3 (2), −H (3), −Br (4), −Cl (5), −F (6)]. CuCl catalyzed olefination of 1−6 with CCl4 in the presence of tetramethylethylenediamine (TMEDA) in DMSO leads to (E)-1-(2,2-dichloro-1-(2-nitrophenyl)vinyl)-2-(para-substituted phenyl)-diazenes [−OCH3 (7), −CH3 (8), −H (9), −Br (10), −Cl (11), −F (12)], respectively. 1–12 were characterized by 1H and 13C NMR spectroscopies, ESI-MS, elemental and X-ray diffraction (for 8, 9 and 12) analysis. The single crystal X-ray analysis of 8, 9 and 12 evidence the intramolecular N⋯Cl pnicogen bonds which is significantly strengthened in view of the planarity of the four atoms involved in the 1,4-membered synthon. The intermolecular halogen and hydrogen bonds also contribute to stabilize the crystal structures of 8, 9 and 12. In DMSO solution 1–12 exist in the E-isomeric form, which stabilized by inter- and intramolecular noncovalent interactions. Solvatochromic behavior on UV–vis absorption spectra of azo dyes 7–12 were studied in CH2Cl2, DMF and MeOH, which λmax is dependent on the attached substituents at para- position of aromatic moiety.

Two known lanthanide complexes, [KLa(HL 1 ) 2 {(CH 3 ) 2 NCHO} 2 (H 2 O) 3 ] ( 1 ) and [Sm(H 2 O) 9 ]( E -H 2 L 2 ) 3 ·2H 2 O ( 2 ) were prepared by reaction of lanthanum(III) and samarium(III) nitrates with potassium 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonate (KH 2 L 1 ) and potassium ( E,Z )-5-chloro-3-(2-(1,3-dioxo-1-phenylbutan-2-ylidene)hydrazinyl)-2-hydroxybenzenesulfonate (KH 2 L 2 ), respectively. Catalytic activities of 1 and 2 were evaluated in the cyanosilylation of aldehydes with trimethylsilyl cyanide in different solvents such as tetrahydrofuran, dichloromethane or methanol. Complex 1 was found to be efficient catalyst for the cyanosilylation reaction in methanol medium at room temperature, producing cyanohydrin trimethylsilyl ethers with good yields (76–99%).

The synthesis and crystal structure of the new tetranuclear diphenyltin(IV) compound [{SnPh2}{SnPh2(OCOMe)}(μ2-OMe)(μ3-O)]2 (1), generated from the reaction of [SnPh2Cl2] and NaOCOMe, are described. Single crystal X-ray diffraction revealed that 1 is a tetranuclear complex with four diphenyltin(IV) units which are inter-connected by μ3-oxido and μ2-methoxido bridges leading to a ladder-like Sn4O4 cluster. Structural comparison with related compounds found in crystallographic data base (CSD) attests that such tetranuclear systems are more abundant than related oxido bridged dimers or trimers. Complex 1 efficiently catalyzes the aerobic Baeyer-Villiger oxidation of cyclohexanone to e-caprolactone, under mild conditions. With the sacrificial benzaldehyde method, quantitative conversion was observed in just 30 min with a remarkable selectivity.

Two known organotin(IV) complexes, [Sn(C6H5)3HL1] (1, H2L1 = 2-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)benzoic acid) and [Sn(C2H5)2(1κO,2κO-H3L2) (1κO2-H3L2) (μ3-O)]2 (2, H4L2 = 2-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazinyl)benzoic acid) were synthesized. Both compounds 1 and 2 act as homogenous catalysts for the diastereoselective nitroaldol (Henry) reaction of aliphatic and aromatic aldehydes with nitroethane in different solvents such as dichloromethane, acetonitrile or methanol. Complex 2 was found to be the more efficient catalyst for the Henry reaction in methanol, producing β-nitroalcohols with good yields (65−89%) and diastereoselectivities (syn/anti 72:28−77:23).

Reaction of bis(4-hydrazinylphenyl)methane with 4-substitutedbenzaldehyde in the presence of CH3COONa in EtOH at 80 °C yields bis(4-((E)-2-(4-substitutedbenzylidene)hydrazinyl)phenyl) methane [−N(CH3)2 1, −F 2, −Cl 3, −NO2 4], which subsequently in the presence of CCl4, CuCl and tetramethylethylenediamine in DMSO undergoes Cu-catalyzed olefination products, bis(4-((E)-(2,2-dichloro-1-(4-substitutedphenyl)vinyl)diazenyl)phenyl)methane [−N(CH3)2 5, −F 6, −Cl 7, −NO2 8], respectively. All compounds were characterized by IR (for 1–4), 1H and 13C NMR spectroscopies, elemental and X-ray diffraction analysis (for 7 and 8). No only intermolecular hydrogen and intramolecular N⋯Cl tetrel bonds, but also the Cl⋯Cl and Cl⋯O types of halogen binding were found in the structures of 7 and 8, respectively. The collected data confirm that bis-azodyes 5–8 exist in DMSO solution and in solid state exclusively in the E-isomeric form, being stabilized by noncovalent interactions. Solvent effects on the UV–vis absorption spectra of 5−8 were studied in CH2Cl2, DMF and EtOH, which λmax is dependent on the type of substituents attached para-position of aromatic moiety.

The new mixed ligand copper(II) complexes [Cu(HL)(H2O)(A)]·2H2O (1, NaH2L = sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzenesulfonate, A = dimethylsulfoxide, [Cu(HL)(H2O)(B)] (2, B = 1,3,4-thiadiazol-2-amine), [Cu(HL)(H2O)(Y)]·1/2CH3OH (3, C = hexamethylenetetramine) and [Cu(HR)2(H2O)2](H2L)2 (4, HR = methyl picolinimidate derived from 2-cyanopyridine) were synthesized and characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. These compounds act as homogenous catalysts for the cyanosilylation reaction of a variety of both aromatic and aliphatic aldehydes with trimethylsilyl cyanide affording the corresponding cyanohydrin trimethylsilyl ethers in high yields (up to 85–99 %) in methanol and at room temperature.

The possibility of using supercritical CO2 (scCO2) technology as a second step for extracting propylene carbonate produced from the coupling reaction between propylene oxide and CO2, was investigated. The coupling reaction was performed under biphasic gas-liquid conditions, using a zinc(II) complex of arylhydrazones of β-diketones (Zn(II)-AHBD) as metal catalyst, combined with tetrabutylammonium bromide (TBABr). 1-Ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]) and methyltrioctylammonium chloride ([ALIQUAT][Cl]) were explored as reaction solvents, in order to efficiently solubilize the catalyst and retain the catalyst inside the reactor during the product extraction step. Results obtained were compared with other common used solvents as methyl ethyl ketone (MEK), ethyl lactate (EL), and polyethylene glycol 400 (PEG 400). [ALIQUAT][Cl] was selected as the most promising solvent and scCO2 extraction was effectively applied as a second step to isolate propylene carbonate from the catalyst system. Following this strategy, the catalyst system was reused three times, without loss of activity.

Reaction of (3a RS ,6 SR ,7a RS )-6-substituted 2-phenyl-2,3,7,7a-tetrahydro-3a,6-epoxyisoindol-1(6 H )-ones ( 1 – 3 ) with ICl (or Br 2 ) in CH 2 Cl 2 yields to halogenated Wagner-Meerwein rearrangement products, 4,5- (or 4,5,6)-halo-2-phenyloctahydro-4,6-epoxycyclopenta[ c ]pyridin-1-ones, with moderate yields (40–43%) of 4 – 6 . All these polyhalogenated compounds are formed exclusively in the syn diastereomeric form relatively to halogen atoms at 4 and 5 positions of molecule. In 4 – 6 the halogenated carbon atoms exist as the S -stereogenic centers. The Cl ⋯ Cl and Cl ⋯ I types of halogen binding were found in the structures of 5 and 6 , respectively, whereas molecules of 4 are stabilized in crystal by multiple hydrogen bonding.

The new mononuclear nickel(II) complexes [Ni(HL 1 )(H 2 O) 2 (CH 3 OH)] ( 1 , NaH 2 L 1 = sodium ( Z )-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzenesulfonate) and [Ni(H 2 L 2 ) 2 (H 2 O) 4 ] [(CH 3 ) 2 S O) 2 ] ( 2 , H 3 L 2 = (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzoic acid) were synthesized and characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. Both compounds 1 and 2 act as homogenous catalysts for the diastereoselective nitroaldol (Henry) reaction of aliphatic and aromatic aldehydes with nitroethane in different solvents such as acetonitrile, methanol or water. Complex 1 was found to be the more efficient catalyst for the Henry reaction in aqueous medium, providing β-nitroalcohols with good yields (67–82%) and diastereoselectivities ( syn/anti 59:41–70:30).

Welcome to this themed collection of RSC articles entitled: 1st International Conference on Noncovalent Interactions.

Producción Científica, In this work, the ionic liquid [Aliquat][Cl] was supported into alginate and silica aerogel matrices and applied as a catalyst in the cycloaddition reaction between CO2 and a bio-based epoxide (limonene oxide). The efficiency of the alginate aerogel system is much higher than that of the silica one. The method of wet impregnation was used for the impregnation of the aerogel with [Aliquat][Cl] and a zinc complex. The procedure originated a well-defined thin solvent film on the surface of support materials. Final materials were characterised by Fourier Transform Infrared Spectroscopy, N2 Adsorption–Desorption Analysis, X-ray diffraction, atomic absorption and Field Emission Scanning Microscopy. Several catalytic tests were performed in a high-pressure apparatus at 353.2 K and 4 MPa of CO2.

cis-[PdCl2(CNR)(PPh3)] [R = Cy, t-Bu, C(Me)2CH2C(Me)3] have been synthesized via the interaction of [(PPh3)ClPd(μ-Cl)2PdCl(PPh3)] with isocyanide in CH2Cl2 at room temperature with 90–98% yield and characterized by means of mass spectrometry as well as 1H, 13C{1H, 31P}, and 31P{1H} NMR spectroscopy. The complexes structure in the solid phase has been elucidated by means of X-ray diffraction analysis. Dynamic processes in the solutions of the complexes in CDCl3 and CD2Cl2 at temperature of–95 to 60°С have been studied by means of 1H and 31P NMR spectroscopy. It has been found that the studied compounds existed exclusively in the cis-[PdCl2(CNR)(PPh3)] form in the solutions. In the case of cis-[PdCl2(CNCy)(PPh3)] in CH2Cl2, the conformational transitions of the equilibrium forms (the transition of the substituent in the cyclohexyl cycle between the equatorial and axial positions) are slowed down, the equatorial conformer prevailing in the solution (2: 1 at–95°С). Quantum-chemical simulation (DFT) has revealed that the standard Gibbs energy of the conformational transition from the axial form of cis-[PdCl2(CNCy)(PPh3)] into the equatorial one in the CH2Cl2 solution at 178 K equals–2.5 kJ/mol, being in agreement with the experimental data.

The 1D and the 2D copper(II) coordination polymers [{Cu(κN,OO′-L)}2(μ-1κN:2κN′-bpy)2]n (1) and [{Cu(μ-1κN,OO′:2κO″-L)}2(μ-1κN:2κN′-hmt)]n (2), respectively, were synthesized from copper(II) nitrate and sodium 2-(2-(1,3-dioxo-1H-inden-2(3H)-ylidene) hydrazinyl)benzenesulfonate (NaHL), in the presence of 4,4′-bipyridine (4,4′-bpy) (for 1) or hexamethylenetetramine (hmt) (for 2). 1 and 2 are water soluble and are characterized by elemental analysis, IR spectroscopy, ESI-MS and single crystal X-ray diffraction. Depending on the neutral linkers, the dianionic ligand L2− displays tri- (in 1) or tetradentate (in 2) binding modes. The Cu2+ in 1 adopts a distorted N3O2 square-pyramid coordination environment, while in 2 it displays a distorted N2O3 trigonal bipyramid geometry. The catalytic activity of 1 and 2 was evaluated in the diastereoselective Henry reaction of nitroethane with a variety of aromatic and aliphatic aldehydes, in water and in organic solvents. β-Hydroxy nitroalkanes were obtained in high yields (up to 92%), and moderate-to-good syn/anti diastereoselectivities (up to 79:21), in water at room temperature.

This review describes how non-covalent interactions, such as hydrogen (inter- and intramolecular, resonance- and charge-assisted hydrogen bonding), halogen, chalcogen and pnicogen bonds, π-interactions, as well as other types of weak forces can influence and control the reactions in the synthesis, e.g., of metal-containing supramolecular networks, providing a class of highly directional stabilizing contacts that can be exploited in the design of coordination compounds. The selected recent examples show that both inter- and intramolecular non-covalent interactions can influence the formation of coordination compounds. This overview of non-covalent interactions applied for synthesis and design of coordination compounds also contributes to an improved understanding of their behavior in crystal engineering, catalysis, etc. It provides a practical consultation for synthetic chemists that are interested in exploring and further developing non-covalent interactions assisted synthesis and design of coordination compounds.

Reaction of cadmium acetate hydrate with sodium 2-[2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl]terephthalate (Na2HL), in the presence of imidazole (im), leads to the polymeric species [Cd(im)3(µ,η-HL-1κOO′:2κO″O‴)]n (1) that is characterized by IR spectroscopy, elemental analysis, UV–Vis absorption spectroscopy and X-ray diffraction analysis. Complex 1 was successfully tested as catalyst for the peroxidative oxidation of alcohols (1-phenylethanol and cyclohexanol) to the corresponding ketones under microwave irradiation, with no added solvent and under mild conditions. The use of tert-butylhydroperoxide as oxidant, of TEMPO as additive, and a temperature of 80 °C leads in 1 h to a yield of acetophenone (from 1-phenylethanol) of nearly 70% or to a cyclohexanone yield (from cyclohexanol) of 66%. A comparison between the catalytic activity of 1 with those (also studied in this work) shown by Cu(II) complexes bearing the same or related hydrazo ligand is presented.

The new copper(II) complexes [Cu(HL1)(H2O)(CH3OH)] (1, H3L1 = (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzoic acid) and [Cu(HL2)(H2O)(CH3OH)] (2, NaH2L2 = sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzenesulfonate) were synthesized and characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. The coordination environment of the central copper(II) has a square pyramidal geometry, three sites being occupied by (HL1,2)2−, which chelates in the O,N,O fashion, while the two other sites are filled with the water and methanol ligands. Multiple intra- and intermolecular non-covalent interactions between the (HL1,2)2−, water and methanol ligands lead to supramolecular network. Both compounds 1 and 2 act as homogenous catalysts for the cyanosilylation reaction of a variety of both aromatic and aliphatic aldehydes with trimethylsilyl cyanide affording the corresponding cyanohydrin trimethylsilyl ethers in high yields (up to 90%) and at room temperature.

The new 1D copper(II) coordination polymers (CPs) [Cu(μ-L1)(H2O)]n (1, H2L1 = 2-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)benzoic acid) and [Cu(μ-H2L2)(H2O)]n (2, H4L2 = (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)terephthalic acid) and the known zwitterionic 1D CP [Cu2(H2O)2(μ-H2L3)(μ-L3)]n (3, H3L3 = 2-(2-(4,4-dimethyl-2,6-dioxocyclo-hexylidene)hydrazinyl)terephthalic acid) were synthesized and tested as homogeneous catalysts for cyanosilylation of a variety of aldehydes to the corresponding cyanohydrin trimethylsilyl ethers. Among these polymeric catalysts, 3, with a zwitterionic charater, is the most effective one, giving 86–99% yield of the ethers upon reaction of aliphatic and aromatic aldehydes with trimethylsilyl cyanide in methanol at room temperature in 4 h. Non-covalent interactions (cation-π and tetrel bondings) involving the aldehyde substrate are proposed to assist the cyanosilylation reaction.

Sodium 2-(2-(1-cyano-2-oxopropylidene)hydrazinyl)benzenesulfonate (NaHL) was synthesized by azocoupling of diazonium salt of 2-aminobenzenesulfonic acid with 3-oxobutanenitrile and characterized by IR, 1H and 13C NMR spectroscopies and ESI-MS analysis. In dimethylsulfoxide-d6 solution NaHL exists as a mixture of Z- and E-hydrazone forms in the amounts of 96 and 4%, respectively. Treatment of this isomeric mixture with copper(II) nitrate hydrate in the presence of ethylenediamine (en) provides unusual (E,Z) → E switching of NaHL to give [Cu(H2O)2(en)2](HL)2 (1). The process is interpreted on the basis of cooperative ionic interactions and resonance assisted hydrogen bonding (RAHB) → charge assisted hydrogen bonding (CAHB) transition.

Three new water-soluble copper(II) complexes [Cu(HL)(H2O){(CH3)2NCHO}] (1), [Cu(H2L)2(im)4]·CH3OH (2) and [Cu(HL)(CH3OH)]2(μ2-py) (3) were synthesized from copper(II) nitrate and sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazinyl)benzene-sulfonate (NaH2L), in the absence (for 1) and presence of imidazole (im) (for 2) or pyrazine (py) (for 3), and fully characterized. The complexes 1–3 have been tested as stereoselective C H activating catalysts for the model nitroaldol (Henry) condensation of nitroethane with various aldehydes in water. 1 was the most active catalyst affording 64−87% yields with syn/anti diasteroselectivities up to 77:23.

Five isostructural lanthanide MOFs, [Ln(1κOO′,2κO′′,3κO′′′,4κO′′′′-μ4-L)(NO3)(DMF)2]n·n(DMF) {Ln = La3+ (1), Ce3+ (2), Nd3+ (3), Sm3+ (4) and Dy3+ (5); L = 5-[2-{2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene}hydrazinyl]isophthalate; DMF = N,N′-dimethyl formamide}, based on dicarboxyl-functionalized arylhydrazone of barbituric acid were synthesized under solvothermal conditions. They were characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric and X-ray diffraction analyses. Crystal structure analysis revealed that these frameworks possess a similar type of two dimensional (2D) structure with a dinuclear {Ln2(COO−)2} unit acting as a secondary building block. Topological analysis shows that these frameworks display a 3,6-connected kgd; Shubnikov plane (3.6.3.6)/dual net. They exhibit excellent heterogeneous catalytic activities (compound 2 is the most active one) towards the cyanosilylation of aldehydes under solvent-free conditions. These catalysts can be recycled at least up to five cycles without a loss of activity. Compounds 1–5 exhibit luminescence properties in the solid state at room temperature.

Chalcogen bonding is a type of noncovalent interaction in which a covalently bonded chalcogen atom (O, S, Se or Te) acts as an electrophilic species towards a nucleophilic (negative) region(s) in another or in the same molecule. In general, this interaction is strengthened by the presence of an electron-withdrawing group on the electron-acceptor chalcogen atom and upon moving down in the periodic table of elements, from O to Te. Following a short discussion of the phenomenon of chalcogen bonding, this Perspective presents some demonstrative experimental observations in which this bonding is crucial for synthetic transformations, crystal engineering, catalysis and design of materials as synthons/tectons.

Reaction of organoiridium(III)-2-phenylpyridine complex, [Ir(ppy)2(μ-Cl)]2 (ppy = 2-phenylpyridinato-C2,N), with 4-(2-bromophenyl)-1,2,3-thiodiazole (X) or 4-(2-bromophenyl)-1,2,3-selenadiazole (Y) in CH2Cl2 yields to [Ir(ppy)2Cl(X)]·CH2Cl2 (1) or [Ir(ppy)2Cl(Y)] (2), respectively. Both compounds were characterized by characterized by elemental analyses (C, H, N), HRESI+-MS, FTIR, and studied by single-crystal X-ray diffraction. The coordination environment of the central iridium(III) has a distorted octahedral geometry, four sites being occupied by two (ppy)−, which chelates in the C,N fashion, while the two other sites are filled with the Cl− and X (or Y) ligands. The intramolecular S···N and Se···Cl types of chalcogen bonds were found in the structures of 1 and 2, respectively. Compound 1 is also present intramolecular pnicogen bonding and intermolecular halogen bonding (between CH2Cl2 molecules) with the short N···Br (3.160 A) and Cl···Cl (2.187 A) distances. The crystal structures in 1 and 2 are stabilized by medium-strong intermolecular hydrogen bonding interactions.

Over the past few decades, direct functionalization/activation of the C–H bond to C–E (E = C, N, O, S, metal, etc.) bonds has become one of the most valuable and straightforward protocols in modern synthetic chemistry. In parallel, controlling the selectivity remains a central challenge in the catalytic functionalization/activation of C–H bond(s) owing to the subtle differences in the reactivity of the various C–H bonds within the molecule. In this chapter, we discuss the crucial role of noncovalent interactions in C–H bond functionalization in alkanes, alkenes, alkynes, aromatics, heterocyclics, aldehydes and ketones. These weak forces can be powerful tools in the formation/stabilization of intermediates and in controlling the selectivity and outcome of a reaction.