The different functional portions present in the thiosemicarbazone (TSC) scaffold allow for a variety of non-covalent interactions while maintaining considerable conformational flexibility. This review gives an overview of how these weak interactions represent leading factors influencing the self-assembly and crystal packing behaviour of TSC-metal complexes, hence acting as building blocks for crystal engineering, leading to tailored 1D, 2D, and 3D architectures. Moreover, these systems represent a highly versatile class of compounds where non-covalent interactions also play a pivotal role in assessing their functions and the ensuing employment in diverse applications. In this context, we present a comprehensive survey concerning the use of TSC-metal complexes in catalysis, sensing, materials science, and environmental applications. Computational methodologies are presented as complementary tools to elucidate the nature and impact of these non-covalent forces. Overall, TSCs and their metal complexes represent a rich platform for designing advanced functional materials with precisely tunable properties through the strategic exploitation of non-covalent interactions.

The present work focuses on the case of an extremely short intramolecular O-H···O hydrogen bond (H-bond) found in 4-methoxypicolinic acid N-oxide (MPANO). The donor···acceptor separation of 2.403 Å makes the H-bond in MPANO one of the shortest H-bonds known. We elucidated the structure and dynamics of the H-bond by two neutron-based techniques, namely, single-crystal diffraction and inelastic scattering (INS) vibrational spectroscopy. We also utilized conventional infrared (IR) spectroscopy as well as quantum chemical computations on isolated and periodic models. Both the protiated and deuterated variants of MPANO were investigated by INS and IR. All the methods used unequivocally confirm the existence of an extremely short, asymmetric H-bond, with the proton located near yet off the midpoint. The main relevant feature of the IR spectrum is an extremely broad, complex, and red-shifted OH (OD) stretching band spanning between 1800 and 500 cm-1 and centered at about 1360 cm-1, which indicates the presence of extensive anharmonicity and coupling with other H-bond modes. Of the modes characteristic of H-bond dynamics, only the out-of-plane OH (OD) bending can clearly be detected in the INS spectra; it has a relatively high frequency indicative of the strength of the H-bond. The computed structure is in excellent agreement with the diffraction measurement when periodicity is taken into account. The calculated harmonic frequencies show a reasonable match with the observed spectral features, whereby the assignment of the IR and INS spectra is facilitated. The hydrogen stretching frequency, however, appears to be significantly overestimated, on account of the limitations of the harmonic approximation and the complex nature of the short H-bond.

Three new coordination complexes of Cu(II) ions made from two hydrazone ligands, 7-chloro-2-oxo-1,2-dihydroquinoline-3-carbaldehyde-2-furoyl-hydrazone (HL1) and 6-chloro-2-oxo-1,2-dihydroquinoline-3-carbaldehyde-2-furoyl-hydrazone (HL2) have been synthesized and fully characterized by spectroscopic techniques. Their crystal and molecular structures revealed distorted square pyramidal mononuclear complexes: [(L1)Cu(H2O)2](NO3)·3H2O, 1(NO3), [(L2)Cu(H2O)2](NO3)·2H2O·CH3OH, 2(NO3), and [(L2)Cu(NO3)(CH3OH)]·2CH3OH, 3, comprising the ligand (L1 and L2) in tridentate fashion (ONO) with two water molecules in 1+ and 2+, and a single methanol molecule and a nitrate ion in 3 in their respective copper coordination spheres. EPR spectra in frozen methanol revealed the occurrence of several species arising from different coordination environments. A detailed DFT investigation on the energetics of solvents exchange (H2O, MeOH, and DMSO) and simulation of the EPR parameters showed that the exchange processes occur easily in solution. The value gz indicated the occurrence of a dimeric aggregate for 2+. The new copper complexes exhibited a noticeable antiproliferative activity with IC50 values in the micromolar range against HCT-15, H157, BxPC3, PNS-1, and A431 cell lines and they were found to be 3-fold more effective than cisplatin against pancreatic PSN-1 cell lines. Cross-resistance tests on A2780 and LoVo cancer cell lines and the corresponding multidrug or oxaliplatin resistant sublines showed that complexes 1(NO3) and 2(NO3) were equally cytotoxic to sensitive and resistant cells, thus overcoming multidrug and oxaliplatin resistance.

Low temperature quantum rotation of dihydrogen in RuH 2 (H 2 ) 2 [P(C 5 H 9 ) 3 )] 2 switched to a facile hydride exchange above 150 K.

The reactivity towards dihydrogen of various copper species, in different coordination environments, decorated by the presence of one and two Al atoms in the framework oz zeolite ZSM-5 are investigated by sorption, INS, FTIR and DFT modeling studies.

We have measured the rotational tunneling spectrum of a Cu−ZSM-5 zeolite after loading with H2, by means of inelastic incoherent neutron scattering. The peaks at ±0.80 and ±1.73 cm-1 unambiguously demonstrate the formation of a strongly bound Cu(η2-H2) complex.

Three new 6-methyl-2-oxo-1,2-dihydroquinoline-3-carbaldehyde-thiosemicarbazones-N-4-substituted pro-ligands and their Cu(II) complexes (1, -NH2; 2, -NHMe; 3, -NHEt) have been prepared and characterized. In both the X-ray structures of 1 and 3, two crystallographically independent complex molecules were found that differ either in the nature of weakly metal-binding species (water in 1a and nitrate in 1b) or in the co-ligand (water in 3a and methanol in 3b). Electron Paramagnetic Resonance (EPR) measurements carried out on complexes 1 and 3 confirmed the presence of such different species in the solution. The electrochemical behavior of the pro-ligands and of the complexes was investigated, as well as their biological activity. Complexes 2 and 3 exhibited a high cytotoxicity against human tumor cells and 3D spheroids derived from solid tumors, related to the high cellular uptake. Complexes 2 and 3 also showed a high selectivity towards cancerous cell lines with respect to non-cancerous cell lines and were able to circumvent cisplatin resistance. Via the Transmission Electron Microscopy (TEM) imaging technique, preliminary insights into the biological activity of copper complexes were obtained.

The dihydrogen complex Ru(H-2)(2)H-2(P(C5H9)(3))(2) has been investigated, via ab initio accelerated molecular dynamics, to elucidate the H ligands dynamics and possible reaction paths for H-2/H exchange. We have characterized the free energy landscape associated with the H atoms positional exchange around the Ru centre. From the free energy landscape, we have been able to estimate a barrier of 6 kcal mol(-1) for the H-2/H exchange process. We have also observed a trihydrogen intermediate as a passing state along some of the possible reaction pathways.

Contrasting established bond activation chemistry of oxiranes (epoxides), the unprecedented insertion of a Pt(0) complex into the carbon-carbon bonds of ethylene oxide and other epoxides, generating 3-oxaplatinacyclobutanes under remarkably mild conditions, has been found. Pt(II) neopentyl hydride complex (dtbpm-kappa P-2)Pt(Np)H (1) undergoes first-order reductive elimination of neopentane at ambient temperature in solution, forming a highly reactive species of an overall composition [(dtbpm)Pt(0)] (C). This intermediate inserts into epoxide C-C bonds or, in the absence of substrates, dimerizes to d(10)-d(10) Pt(0) species D. The epoxide activation products have been fully characterized including X-ray structure determinations. Various experiments have been conducted in order to decipher mechanistic details of this unusual chemistry. Theoretical studies on various levels do not allow a reliable conclusion as to the actual nature of the reactive intermediate C. Both conceivable structures Cl (ring-opened [(dtbpm-kappa P-1)Pt(0), d(10)-ML, 12 VE]) and C2 (chelate, [(dtbpm-kappa P-2)Pt(0)], d(10)-ML2, 14 VE) are minimum-energy structures with a very small (method-dependent) energy difference.

Three new 2-oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde terminal substituted aroylhydrazone ligands (2-Oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde(2'-hydroxybenzoyl)hydrazine, H(2)L1, 1, 2-Oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde(2'-hydroxybenzoy)hydrazine, H(2)L2, 2, 2-Oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde(2'-hydroxybenzoyl)hydrazine, H(2)L3, 3) and the corresponding novel copper(II) complexes (Cu(L)(CH3OH)(NO3)1(L = HL1 (4), HL2 (5), HL3 (6-6(+)), have been synthesized to compare their coordination behaviour and biological activity with respect to the presence of an OH group in different positions of the phenyl ring in the hydrazone moieties. The new ligands and their copper complexes were characterized by elemental analysis and spectroscopic techniques. The molecular structures of the new complexes 4 and 6-6(+) were determined by single crystal X-ray diffraction. The interactions of the free ligands and their copper complexes with calf thymus DNA were tested by absorption measurements and ethidiurn bromide competitive studies which revealed that all compounds may interact with calf thymus DNA through intercalation. Furthermore, a comparative analysis of the cytotoxic effect of the compounds on a panel of human cancer cell lines showed that the copper complexes exhibited in vitro antitumor activity significantly higher than that of the free ligands and also of cisplatin.

The open copper metal sites in CPO-27-Cu were studied by means of IR spectroscopy of adsorbed CO and NO, and density functional theory calculations. Very low Lewis acidity of the Cu2+ sites was established by CO (IR band at 2153-2149 cm(-1)). Variable-temperature IR experiments indicate adsorption enthalpy of ca. -20 kJ mol(-1). It was also found that CO is a sensitive probe of the occupation of the neighboring copper sites. In contrast to the general expectations, NO is very weakly adsorbed on the Cu2+ sites (-14.5 kJ mol(-1), IR band at 1888 cm(-1)). The effect is attributed to the particular Cu2+ ion coordination and electronic state, leading to a large Jan-Teller deformation and low effective charge, preventing significant charge transfer effects between the metal center and the guest molecules as well as any significant electrostatic interactions. Thus, dominating are van der Waals interactions which position the adsorbed molecule relatively far away at about 2.7-3.0 angstrom. Adsorption of CO also revealed that a small fraction of the copper ions are found in the Cu(+ )state (IR band at 2120 cm(-1)), and these sites were associated with and modeled as defect undercoordinated sites most probably located at the terminal crystallite surfaces. A small fraction of adsorbed NO was relatively strongly adsorbed (-35 kJ mol(-)(l)) and associated with the same set of defect copper sites.

A combined experimental and theoretical study of H-2 sorption was carried out on two isostructural zeolitic imidazolate frameworks. (ZIFs), namely ZIF-68 and ZIF-69. The former consists of Zn2+ ions that are coordinated to two 2-nitroimidazolate and two benzimidazolate linkers in a tetrahedral fashion, while 5-chlorobenzimidazolate is used in place of benzimidazolate in the latter compound. H-2 sorption measurements showed that the two ZIFs display similar isotherms and isosteric heats of adsorption (Q(st)). The experimental initial H-2 Q(st) value for both ZIFs was determined to be 8.1 kJ mol(-1), which is quite high for materials that do not contain exposed metal centers. Molecular simulations of H-2 sorption in ZIF-68 and ZIF-69 confirmed the similar H-2 sorption properties between the two ZIFs, but also suggest that H-2 sorption is slightly favored in ZIF-68 with regards to uptake at 77 K/1.0 atm. This work also presents inelastic neutron scattering (INS) spectra for H-2 sorbed in ZIFs for the first time. The spectra for ZIF-68 and ZIF-69 show a broad range of intensities starting from about 4 meV. The most favorable H-2 sorption site in both ZIFs corresponds to a confined region between two adjacent 2-nitroimidazolate linkers. Two-dimensional quantum rotation calculations for H-2 sorbed at this site in ZIF-68 and ZIF-69 produced rotational transitions that are in accord with the lowest energy peak observed in the INS spectrum for the respective ZIFs. We found that the primary binding site for H-2 in the two ZIFs generates high barriers to rotation for the adsorbed H-2, which are greater than those in several metal organic frameworks (MOFs) which possess open-metal sites. H-2 sorption was also observed for both ZIFs in the vicinity of the nitro groups of the 2-nitroimidazolate linkers. This study' highlights the constructive interplay of experiment and theory to elucidate critical details of the H-2 sorption mechanism in these two isostructural ZIFs.

A combined experimental and theoretical study provides a rationale of the chemical and physical behavior for Pt(II)-acetonitrile and -benzonitrile complexes. The increased reactivity of the nitrile ligands, after coordination to Pt(II), can be explained by the energy decreasing of the ligands’ LUMOs. The theoretical models are able to reproduce the spectroscopic observations and show an excellent agreement between crystallographic data and optimized structures, nicely supporting the proposed models.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

N-Palmitoyl-ethanolamine (PEA) is an anti-inflammatory component of egg yolk that is usually employed for the prevention of respiratory apparatus virus infection and then frequently used for its efficient anti-inflammatory and analgesic effects in experimental models of visceral, neuropathic, and inflammatory diseases. Nevertheless, data of its use in animal or human therapy are still scarce and further studies are needed. Herein, we report the biological evaluation of a small library of N-palmitoyl-ethanolamine analogues or derivatives, characterized by a protected acid function (either as palmitoyl amides or hexadecyl esters), useful to decrease their hydrolysis rate in vitro and prolong their biological activity. Two of these compounds—namely phenyl-carbamic acid hexadecyl ester (4) and 2-methyl-pentadecanoic acid (4-nitro-phenyl)-amide (5)—have shown good anti-inflammatory and antioxidant properties, without affecting the viability of J774A.1 macrophages. Finally, crystals suitable for X-ray analysis of compound 4 have been obtained, and its solved crystal structure is here reported. Our outcomes may be helpful for a rational drug design based on new PEA analogues/derivatives with improved biological properties.

Some critical issues concerning the complex synthesis and crystallization of designed coordination polymers are highlighted by using gels as diffusion media. The systematic use of gel methods in a variety of different crystallization configurations has been proven useful in revealing the field of existence and the stability hierarchy of competitive and concomitant crystalline phases, and also in discovering some important effects due to gel matrices. The most interesting phenomena observed are the modification and alteration of the macro- and microscopic morphology of crystals due to gel incorporation, which are responsible for changes in many properties and functionalities of these materials, opening up new possibilities for their applications in a variety of technological fields. In addition, a kinetic study of a gel grown polymeric system has also been conducted, demonstrating the continuous evolution of crystal morphology and its connection with the crystal growth process and growth mechanism.

Metal-organic frameworks (MOFs) possessing open metal sites (e.g., from the CPO-27 series) are a promising class of materials for hydrogen storage. However, there is still no consensus on the vibrational signatures of H-2 adsorbed on different sites. In this work we report results of a combined Fourier transform infrared (FTIR) spectroscopy and density functional theory (DFT) study on H-2 adsorption on dehydrated and D2O-precovered CPO-27-Ni. For unambiguous interpretation of the results adsorption of CO was also studied. Low-temperature CO adsorption on dehydrated CPO-27-Ni results in formation of Ni2+-CO adducts stabilized by pi-back-donation and characterized by a CO stretching frequency at 2182 cm(-1) (low coverage). With D2O-precovered a sample CO replaces part of the preadsorbed D2O molecules, and in this case the nu(CO) is significantly lowered (2172 cm(-1)). When H-2 is adsorbed at 100 K on dehydrated sample, complexes involving Ni2+ sites are formed and characterized by a nu(H-H) band at 4031 cm(-1). A satellite band (Q(trans) mode) is detected at 4249 cm(-1). Similar results were obtained after D-2 adsorption. However, D-2 was more strongly adsorbed than H-2 and the Qtrans mode was of lower relative intensity. Only at high H-2/D-2 equilibrium pressures (>= 50 mbar) occupation of secondary sites was clearly detected by a nu(H-H) band at 4118 cm(-1) or nu(D-D) band at 2964 cm(-1). No significant differences in the strength of adsorption of H-2 and D-2 were detected in this case, suggesting the mode of adsorption is different from that realized for the complexes involving Ni2+ sites. Progressive filling of the Ni2+ sites by D2O leads to a strong decrease in intensity of the H-2/D-2 bands associated with Ni2+ sites and red shift of their frequencies indicating a decrease of the interaction strength. On the contrary, the bands due to H-2/D-2 interaction with secondary sites appear with enhanced intensities and are blue-shifted, which suggests an increase of the interaction strength. These results were confirmed by DFT calculations showing an increase of the H-2 adsorption enthalpy on secondary sites (identified as framework oxygen atoms) in the presence of water due to attractive interaction of H-2 with the nearby water molecule. Spectral evidence of direct interaction of adsorbed H-2/D-2 with adsorbed water was also found. Our results allow confirming that H-2 adsorbed on open Ni2+ sites is characterized by a stretching frequency lower than 4100 cm(-1) and some proposed values of Mn+-H-2 adducts above 4100 cm(-1) are in fact due to H-2 interacting with secondary sites affected by H2O located in the vicinity.

The use of gels or viscous materials as growth media for a wide range of compounds, including proteins, inorganic and organic compounds has already been reported in the literature. In the presence of a gel, sedimentation and convection currents are greatly suppressed and the mass transport of the molecules occurs mainly by diffusion. As a result, a lower nucleation density and a better crystal quality are usually observed.[1a] We report, here, new interesting phenomena observed in crystallization experiments of coordination compounds by using gels as diffusion media.[1b].

Three new N-heterocyclic-silazane compounds, 1a-c, were prepared and employed as bidentate ligands to ruthenium, resulting in a series of [Ru(H){(κ-Si,N-(SiMe2-N-heterocycle)}3] complexes (3a-c) featuring the same RuSi3H motif. Detailed structural characterization of the RuSi3H complexes with X-ray diffraction, and in the case of triazabicyclo complex [Ru(H){κ-Si,N-(SiMe2)(C7H12N3)}3] (3a), neutron diffraction, enabled a reliable description of the molecular geometry. The hydride ligand of (3a) is located closer to two of the silicon atoms than it is to the third. Such a geometry differs from that of the previously reported complex [Ru(H){(κ-Si,N-(SiMe2)N(SiMe2H)(C5H4N)}3] (3d), also characterized by neutron diffraction, where the hydride was found to be equidistant from all three silicon atoms. A DFT study revealed that the symmetric and less regular isomers are essentially degenerate. Information on the dynamics and on the Ru···H···Si interactions was gained from multinuclear solid-state ((1)H wPMLG, (29)Si CP MAS, and 2D (1)H-(29)Si dipolar HETCOR experiments) and solution NMR studies. The corresponding intermediate complexes, [Ru{κ-Si,N-(SiMe2-N-heterocycle)}(η(4)-C8H12)(η(3)-C8H11)] (2a-c), involving a single silazane ligand were isolated and characterized by multinuclear NMR and X-ray diffraction. Protonation of the RuSi3H complexes was also studied. Reaction of 3a with NH4PF6 gave rise to [Ru(H)(η(2)-H -SiMe2)κ-N-(C7H12N3){κ-Si,N-(SiMe2)(C7H12N3)}2](+)[PF6](-)(4aPF6) which was isolated and characterized by NMR spectroscopy, X-ray crystallography, and DFT studies. The nature of the Si-H interactions in this silazane series was analyzed in detail.