C‒H‒O Hydrogen Bonding in Crystals

Modulation of the strength of weak S-H⋯O hydrogen-bond: Spectroscopic study of the complexes of 2-flurothiophenol with methanol and ethanol

Spectroscopic exploration of sulfur-centered hydrogen bonding involving a thiol group (S-H) as the hydrogen bond donor is scarce in the literature. Herein, we have investigated 1:1 complexes of 2-fluorothiophenol (2-FTP) with methanol (MeOH) and ethanol (EtOH) in the gas phase to examine the physical characteristics and strength of the S-H⋯O hydrogen bond. Structures, conformations, and the strength of the S-H⋯O interaction are investigated by measuring the electronic and Infrared (IR) spectra of the two complexes employing resonant two-photon ionization, UV-UV hole-burning, and IR-UV double resonance spectroscopic techniques combined with quantum chemical calculations. Three conformers of 2-FTP⋯MeOH and two conformers of 2-FTP⋯EtOH have been detected in the experiment. A comparison of the IR spectra obtained from the experiment with those of the low-energy conformers of 2-FTP⋯MeOH and 2-FTP⋯EtOH predicted from the theory confirms that all the observed conformers of the two complexes are primarily S-H⋯O hydrogen bonded. The IR red-shifts found in the S-H stretching frequencies in 2-FTP⋯MeOH and 2-FTP⋯EtOH concerning that in 2-FTP are ∼76 and ∼88 cm-1, respectively, which are much larger than that was reported earlier in the 2-FTP⋯H2O complex (30 cm-1). The strength and physical nature of different noncovalent interactions, including the S-H⋯O hydrogen bond existing in the complexes, are further analyzed using natural bond orbital analysis, quantum theory of atoms in molecules, and localized molecular orbital-energy decomposition analysis. The current investigation reveals that the S-H⋯O hydrogen bond can be strengthened by judicial choices of the hydrogen bond acceptors of higher proton affinities.

Exploring the self-assembly dynamics of novel steroid-coumarin conjugates: a comprehensive spectroscopic and solid-state investigation

The design, synthesis, and characterization of seven novel steroid-coumarin conjugates with diverse steroidal nuclei as lipophilic fluorescent materials for bioimaging applications are presented. The conjugates were synthesized through amidation, characterized using spectroscopic and spectrometric methods, and their main photophysical properties were determined. Dioxane : water titration experiments revealed their ability to self-assemble, forming J-aggregates as evidenced by new spectral bands at higher wavelengths. Monocrystal X-ray diffraction analysis disclosed distinctive aggregation patterns exhibiting J- or H-aggregates for selected compounds. Bioimaging studies demonstrated cell membrane localization for most conjugates, with some of them displaying an interesting selectivity for lipid droplets. Notably, the presence of the steroid fragments significantly influenced both the self-assembly patterns and the cellular localization of the fluorescent probes.

trans-Di-chlorido-bis-[(S)-(-)-1-(4-methyl-phen-yl)ethyl-amine-κN]palladium(II)

The title complex, [PdCl2(C9H13N)2], comprises a single mol-ecule in the asymmetric unit. The PdII atom is tetra-coordinated by two N atoms from two trans-aligned organic ligands and two Cl ligands, forming a square-planar metal coordination environment. The distances from the ortho-H atoms on the phenyl ring to the central PdII atom fall within the range 4.70-5.30 Å, precluding any significant intra-molecular Pd⋯H inter-actions.

Oxychloridoselenites(IV) with cubane-derived anions and stepwise chlorine-to-oxygen exchange

The novel oxychloridoselenites(IV) [BMIm][Se₃Cl₁₃] (1), [BMIm][Se₄Cl₁₅O] (2), [BMIm]₂[Se₄Cl₁₄O₂] (3), [BMPyr]₂[Se₄Cl₁₄O₂] (4), [BMPyr]₂[Se₆Cl₁₈O₄] (5), [BMIm]₂[SeCl₄O] (6), [BMPyr]₂[Se₂Cl₆O₂] (7), and [BMPyr]₂[Se₆Cl₁₄O₆] (8) are prepared by ionic-liquid-based synthesis. Accordingly, SeCl₄, SeO₂ (1-6), and/or SeOCl₂ (7,8) as the starting materials are reacted in [BMIm]Cl or [BMPyr]Cl as ionic liquid (BMIm: 1-butyl-3-methylimidazolium, BMPyr: 1-butyl-1-methylpyrrolidinium; partially with AlCl₃ in addition). Generally, the composition and structure of title compounds can be derived from the tetrameric, heterocubane-type (SeCl₄)₄ as the initial building unit. Thus, chlorine is successively exchanged by oxygen from 1 to 8. Moreover, the four edge-sharing (SeCl₆) octahedra in (SeCl₄)₄ are increasingly dismantled, ending with a [SeCl₄O]^2- anion as a single pseudo-octahedron in 6. Based on the weakly coordinating ionic liquid, it is possible to selectively obtain the different species via synthesis near room temperature (20-80 °C). The oxychloridoselenite anions [Se₄Cl₁₅O]^-, [Se₄Cl₁₄O₂]^2-, [Se₆Cl₁₈O₄]^2-, and [Se₆Cl₁₄O₆]^2- are obtained for the first time. The title compounds are characterized by X-ray structure analysis based on single crystals and powders as well as by infrared spectroscopy and thermal analysis.

Crystal structure of 8-hexyloxy-2-[(Z)-2-(naphthalen-2-yl)ethenyl]quinoline

In the title mol­ecule, C₂₇H₂₇NO, the naphthalene and quinoline groups are both planar and subtend a dihedral angle of 15.47 (7)°. They are nearly coplanar with the cis-vinyl bridge and the hex­yloxy chain, which adopts an all-trans conformation, resulting in transannular bifurcated intra­molecular C—H⋯N,O contact. The crystal structure features γ-packing of the aromatic moieties, while the parallel packing of alkyl chains resembles that of alkanes.

In the title mol­ecule, C₂₇H₂₇NO, the naphthalene and quinoline groups are both planar and subtend a dihedral angle of 15.47 (7)°. They are nearly coplanar with the cis-vinyl bridge and the hex­yloxy chain, which adopts an all-trans conformation, resulting in transannular bifurcated intra­molecular C—H⋯N,O contact. The crystal structure features γ-packing of the aromatic moieties, while the parallel packing of alkyl chains resembles that of alkanes.

Spectroscopic and Computational Studies on a Dansyl Based Luminescent Probe: Detection of Water Contaminant in Hygroscopic Deuterated Solvents

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A Dansyl functionalized fluorescent probe (DFFP) has been intended, synthesized, and well-characterized (NMR, IR, Mass, SEM, SCXRD), capable of sensing trace amounts of water contaminant in hygroscopic deuterated solvents by changing colour under UV irradiation. A distinct bathochromic shift in emission spectra of probe DFFP and the visual colour change (Green to Yellow) under UV lamp are the key evidence of the presence of water contaminant. To prove the potentiality of the probe while detecting the remnant water, we did some experimental studies along with exhaustive theoretical evaluation. DFT (Energy optimization and other calculations) helped in better understanding the sensing mechanism and the mode of interactions among probe-water-solvent. Total electron density mapped over Electrostatic Potential Surface and calculation of ESP charges helped in locating more electron-dense regions in the ground state. The involvement of TD-DFT studies helped in finding the possible electronic transitions and corresponding absorption bands. Moreover, the probe is capable of sensing ethanolic water vapour in the gaseous phase. Due to high fluorescence and being nontoxic to cells, probe DFFP could be used as a potential cell imaging dye. It has been employed in a human cancer cell line (A549), and fluorescent confocal microscopic images were obtained.

The crystal structure of 3,3′-[1,4-phenylenebis(methylene)]bis(1-ethenyl-1H-imidazol-3-ium) dichloride – dichloromethane – water (1/1/1), C19H24Cl4N4O1

C19H24Cl4N4O1, triclinic, P 1 ‾ $P‾{1}$ (no. 2), a = 8.5930(4) Å, b = 12.0814(5) Å, c = 12.2430(5) Å, α = 69.805(2)°, β = 75.2820(10)°, γ = 86.733(2)°, V = 1153.07(9) Å3, Z = 2, R gt (F) = 0.0411, wR ref (F 2) = 0.1053, T = 296 K.

Non-Coordinated Phenolate Anions and Their Application in SF6 Activation

The reaction of the strong monophosphazene base with the weakly acidic phenol leads to the formation of a phenol-phenolate anion with a moderately strong hydrogen bond. Application of the more powerful tetraphosphazene base (Schwesinger base) renders the isolation of the corresponding salt with a free phenolate anion possible. This compound represents the first species featuring the free phenolate anion [H5 C6 -O]- . The deprotonation of phenol derivatives with tetraphosphazene bases represents a great way for the clean preparation of salts featuring free phenolate anions and in addition allows the selective syntheses of hydrogen bonded phenol-phenolate salts. This work presents a phosphazenium phenolate salt with a redox potential of -0.72 V and its capability for the selective activation of the chemically inert greenhouse gas SF6 . The performed two-electron reduction of SF6 leads to phosphazenium pentafluorosulfanide ([SF5 ]- ) and fluoride salts.

Sterically constrained tricyclic phosphine: redox behaviour, reductive and oxidative cleavage of P-C bonds, generation of a dilithium phosphaindole as a promising synthon in phosphine chemistry

The redox behaviour of sterically constrained tricyclic phosphine 3a was investigated by spectroelectrochemistry. The data suggested a highly negative reduction potential with the reversible formation of a dianionic species. Accordingly, 3a reacted with two equivalents of Li/naphthalene by reductive cleavage of a P-C bond of one of the PC4 heterocycles. The resulting dilithium compound 5 represents a phosphaindole derivative with annulated aromatic C6 and PC4 rings. It is an interesting starting material for the synthesis of new heterocyclic molecules, as was shown by treatment with Me2SiCl2 and PhPCl2. The structures of the products (6 and 7) formally reflect ring expansion by insertion of silylen or phosphinidene fragments into a P-C bond of 3a. Treatment of 3a with H2O2 did not result in the usually observed transfer of a single O atom to phosphorus, but oxidative cleavage of a strained PC4 ring afforded a bicyclic phosphinic acid, R2PO2H.

The Influence of Weakly Coordinating Cations on the O-H⋅⋅⋅O- Hydrogen Bond of Silanol-Silanolate Anions

The reaction of a saline phosphazenium hydroxide hydrate with siloxanes led to a novel kind of silanol-silanolate anions. The weakly coordinating behavior of the cation renders the formation of silanol-silanolate hydrogen bonds possible, which otherwise suffer from detrimental silanolate-oxygen cation interactions. We investigated the influence of various weakly coordinating cations on silanol-silanolate motifs, particularly with regard to different cation sizes. While large cations favor the formation of intramolecular hydrogen bonds resulting in cyclic structures, the less bulky tetramethyl ammonium cation encourages the formation of polyanionic silanol-silanolate chains in the solid state.

Synthesis, X-ray characterization and theoretical study of all-cis 1,4:2,3:5,8:6,7-tetraepoxynaphthalenes: on the importance of the through-space α-effect

This manuscript reports the synthesis, X-ray characterization and theoretical study of all-cis 1,4:2,3:5,8:6,7-tetraepoxynaphthalenes focusing on the importance of α-effect hydrogen bonds.

Al/N-based active Lewis pairs: isocyanate insertion products as efficient nucleophiles employed for the facile generation of highly functional molecules

The previously reported active Lewis pair (ALP) i Bu2Al–N(2-Ad)NC5H10 (1) (2-Ad = 2-adamantyl) is readily accessible by hydroalumination of the hydrazone H10C5N–N=(2-C10H14) with H–Al i Bu2. Treatment of 1 with two equivalents of isocyanates R-N=C=O yields six-membered AlC2N2O heterocycles 2 (2a, R = Ph; 2b, R = p-Tol) by dual insertion into the Al–N bonds. 2a reacts as a nucleophile with carboxylic acid chlorides R-C(O)–Cl [R = CH2 t Bu, p-Tol, H2CCH(Me)C6H4(4-CH2CHMe2) (Ibu-profen acid chloride), 0.5 (1,4-C6H4)] to afford by elimination of i Bu2AlCl and hydrolysis new triuret derivatives R-C(O)[N(Ph)C(O)]2–N(2-Ad)NC5H10 (3a to 3d) as colourless, sparingly soluble solids in moderate (3c) to high (3b) yields. The analogous reaction of 2a with (p-Tol)–C(Cl)=N(p-Tol) leads to the imidoyl derivative (p-Tol)N=C(p-Tol)[N(Ph)C(O)]2–N(2-Ad)NC5H10 (4a), which showed a fast exchange of phenyl and tolyl groups to yield a mixture of isomers. The analogous reaction of 2b affords the corresponding compound 4b for which a single isomer is isolated despite the scrambling of substituents.

Syntheses and crystal structures of the anhydride 4-oxa-tetra-cyclo-[5.3.2.02,6.08,10]dodec-11-ene-3,5-dione and the related imide 4-(4-bromo-phen-yl)-4-aza-tetra-cyclo-[5.3.2.02,6.08,10]dodec-11-ene-3,5-dione

The Diels–Alder cyclo­addition of cyclo­hepta­triene and maleic anhydride produces the title carb­oxy­lic anhydride; reaction of this anhydride with 4-bromo­phenyl­aniline forms the corresponding tetra­cyclic imide. The anhydride features C—H⋯O hydrogen bonds in the solid state, while the imide also features C—H⋯O hydrogen bonds as well as C—H⋯π and lone pair–π inter­actions.

The syntheses and crystal structures of the two title compounds, C₁₁H₁₀O₃ (I) and C₁₇H₁₄BrNO₂ (II), both containing the bi­cyclo­[2.2.2]octene ring system, are reported here [the structure of I has been reported previously: White & Goh (2014 ▸). Private Communication (refcode HOKRIK). CCDC, Cambridge, England]. The bond lengths and angles of the bi­cyclo­[2.2.2]octene ring system are similar for both structures. The imide functional group of II features carbonyl C=O bond lengths of 1.209 (2) and 1.210 (2) Å, with C—N bond lengths of 1.393 (2) and 1.397 (2) Å. The five-membered imide ring is nearly planar, and it is positioned exo relative to the alkene bridgehead carbon atoms of the bi­cyclo­[2.2.2]octene ring system. Non-covalent inter­actions present in the crystal structure of II include a number of C—H⋯O inter­actions. The extended structure of II also features C—H⋯O hydrogen bonds as well as C—H⋯π and lone pair–π inter­actions, which combine together to create supra­molecular sheets.

Methyl 3,3,6,6-tetramethyl-1,8-dioxo-4,5,7,9-tetrahydro-2H-xanthene-9-carboxylate

The title mol­ecule is built by annulation of a half-chair cyclo­hexenone and a twist-cyclo­hexenone to a flat 4-H-pyrane boat. In the crystal, mol­ecules are connected via van der Waals inter­actions and C—H⋯O hydrogen bonds.

The title mol­ecule, C₁₉H₂₄O₅, is built by annulation of a half-chair cyclo­hexenone and a twist-cyclo­hexenone to a flat 4-H-pyrane boat. In the crystal, mol­ecules are connected via van der Waals inter­actions and C—H⋯O hydrogen bonds.

Crystal structure of N,N-diisopropyl-4-methyl-benzene-sulfonamide

The synthesis of the title compound, C13H21NO2S, is reported here along with its crystal structure. This compound crystallizes with two mol-ecules in the asymmetric unit. The sulfonamide functional group of this structure features S=O bond lengths ranging from 1.433 (3) to 1.439 (3) Å, S-C bond lengths of 1.777 (3) and 1.773 (4) Å, and S-N bond lengths of 1.622 (3) and 1.624 (3) Å. When viewing the mol-ecules down the S-N bond, the isopropyl groups are gauche to the aromatic ring. On each mol-ecule, two methyl hydrogen atoms of one isopropyl group are engaged in intra-molecular C-H⋯O hydrogen bonds with a nearby sulfonamide oxygen atom. Inter-molecular C-H⋯O hydrogen bonds and C-H⋯π inter-actions link mol-ecules of the title compound in the solid state.

Crystal structure of 4-methyl-N-propyl-benzene-sulfonamide

The title compound comprises two mol­ecules in the asymmetric unit. Inter­molecular C—H⋯O and N—H⋯O hydrogen bonds lead to a three-dimensional network structure.

The crystal structure of the title sulfonamide, C₁₀H₁₅NO₂S, comprises two mol­ecules in the asymmetric unit. The S=O bond lengths of the sulfonamide functional group range from 1.428 (2) to 1.441 (2) Å, with S—C bond lengths of 1.766 (3) Å (for both mol­ecules in the asymmetric unit), and S—N bond lengths of 1.618 (2) and 1.622 (3) Å, respectively. When both mol­ecules are viewed down the N—S bond, the propyl group is gauche to the toluene moiety. In the crystal structure, mol­ecules of the title compound are arranged in an intricate three-dimensional network that is formed via inter­molecular C—H⋯O and N—H⋯O hydrogen bonds. The crystal structure was refined from a crystal twinned by inversion.

Crystal structure of 1-[(4-methylbenzene)sulfonyl]pyrrolidine

The mol-ecular structure of the title compound, C11H15NO2S, features a sulfonamide group with S=O bond lengths of 1.4357 (16) and 1.4349 (16) Å, an S-N bond length of 1.625 (2) Å, and an S-C bond length of 1.770 (2) Å. When viewing the mol-ecule down the S-N bond, both N-C bonds of the pyrrolidine ring are oriented gauche to the S-C bond with torsion angles of -65.6 (2)° and 76.2 (2)°. The crystal structure features both intra- and inter-molecular C-H⋯O hydrogen bonds, as well as inter-molecular C-H⋯π and π-π inter-actions, leading to the formation of sheets parallel to the ac plane.

Host-Guest Hydrogen Bonding Varies the Charge-State Behavior of Magnetic Sponges

The electron-donor(D) and -acceptor(A)-assembled D₂ A-layer framework [{Ru₂ (m-FPhCO₂ )₄ }₂ TCNQ(OMe)₂ ]⋅nDCE (1-nDCE; m-FPhCO₂ ^- =m-fluorobenzoate; TCNQ(OMe)₂ =2,5-dimethoxyl-7,7,8,8-tetracyanoquinodimethane; DCE=1,2-dichloroethane) undergoes drastic charge-ordered state variations via three distinct states that are a two-electron-transferred state (2e-I), a charge-disproportionated state (1.5e-I), and a one-electron-transferred state (1e-I), depending on the degree of solvation by nDCE. The pristine form 1-4DCE has a paramagnetic 2e-I state, which eventually produces the solvent-free form 1 in 1.5e-I via an intermediate state 1-nDCE (n≤1) in 1e-I. Resolvation of 1 stabilizes 1-DCE, allowing it to switch between 1.5e-I and 1e-I, and to become ferrimagnetic with a T_c of 30 K (1.5e-I) and 88 K (1e-I). The stabilization of the 1e-I state of 1-DCE is due to the presence of host-guest hydrogen bonding that enables to suppress the electron-donation ability of D even in an identical framework with 1.

(E,E)-3-Methyl-2,5-bis-(4-methyl-benzyl-idene)cyclo-penta-none: synthesis, characterization, Hirshfeld surface analysis and anti-bacterial activity

The title compound, (E,E)-3-methyl-2,5-bis-(4-methyl-benzyl-idene)cyclo-penta-none (MBMCP), C22H22O, was obtained by Claisen-Schmidt condensation of 4-methyl-benzaldehyde with 3-methyl-cyclo-penta-none in good yield. The structure of MBMCP was studied using UV, FT-IR and Raman spectroscopy, single-crystal X-ray diffraction (XRD) measurements, and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The mol-ecular structure of MBMCP is fully extended in the E,E configuration. C-H⋯π stacking inter-actions play a significant role in the stabilization of the mol-ecular packing. Hirshfeld surface analysis was used to qu-antify the non-covalent inter-actions in the crystal lattice. Microbiological studies were performed to investigate the anti-microbial activity of this new product.

N+-C-H···O Hydrogen bonds in protein-ligand complexes

In the context of drug design, C-H···O hydrogen bonds have received little attention so far, mostly because they are considered weak relative to other noncovalent interactions such as O-H···O hydrogen bonds, π/π interactions, and van der Waals interactions. Herein, we demonstrate the significance of hydrogen bonds between C-H groups adjacent to an ammonium cation and an oxygen atom (N⁺-C-H···O hydrogen bonds) in protein-ligand complexes. Quantum chemical calculations revealed details on the strength and geometrical requirements of these N⁺-C-H···O hydrogen bonds, and a subsequent survey of the Protein Data Bank (PDB) based on these criteria suggested that numerous protein-ligand complexes contain such N⁺-C-H···O hydrogen bonds. An ensuing experimental investigation into the G9a-like protein (GLP)-inhibitor complex demonstrated that N⁺-C-H···O hydrogen bonds affect the activity of the inhibitors against the target enzyme. These results should provide the basis for the use of N⁺-C-H···O hydrogen bonds in drug discovery.

A P-H functionalized Al/P-based frustrated Lewis pair - hydrophosphination of nitriles, ring opening with cyclopropenones and evidence of P[double bond, length as m-dash]C double bond formation

Hydroalumination of R-P(H)-C[triple bond, length as m-dash]C-tBu with bulky H-Al[CH(SiMe3)2]2 afforded the new P-H functionalized Al/P-based frustrated Lewis pair R-P(H)-C[[double bond, length as m-dash]C(H)-tBu]-AlR2 [R = CH(SiMe3)2; FLP 7]. A weak adduct of 7 with benzonitrile (8) was detected by NMR spectroscopy, but could not be isolated. tert-Butyl isocyanide afforded a similar, but isolable adduct (9), in which the isocyanide C atom was coordinated to aluminium. The unique reactivity of 7 became evident from its reactions with the heteroatom substituted nitriles PhO-C[triple bond, length as m-dash]N, PhCH2S-C[triple bond, length as m-dash]N and H8C4N-C[triple bond, length as m-dash]N. Hydrophosphination of the C[triple bond, length as m-dash]N triple bonds afforded imines at room temperature which were coordinated to the FLP by Al-N and P-C bonds to yield AlCPCN heterocycles (10 to 12). These processes depend on substrate activation by the FLP. Diphenylcyclopropenone and its sulphur derivative reacted with 7 by addition of the P-H bond to a C-C bond of the strained C3 ring and ring opening to afford the fragment (Z)-Ph-C(H)[double bond, length as m-dash]C(Ph)-C-X-Al (X = O, S). The C-O or C-S groups were coordinated to the FLP to yield AlCPCX heterocycles (13 and 14). The thiocarbonyl derived compound 14 contains an internally stabilized phosphenium cation with a localized P[double bond, length as m-dash]C bond, a trigonal planar coordinated P atom and a short P[double bond, length as m-dash]C distance (168.9 pm). Insight into formation mechanisms, the structural and energetic properties of FLP 7 and compounds 13 and 14 was gained by quantum chemical DFT calculations.

Different packing motifs of isomeric (E)-N'-(halo-phenyl-methyl-idene)-N-methyl-2-(thio-phen-2-yl)acetohydrazides controlled by C-H⋯O inter-actions

The crystal structures of three isomeric (E)-N'-(chloro-phenyl-methyl-idene)-N-methyl-2-(thio-phen-2-yl)acetohydrazides (C14H13ClN2OS) are described, with the Cl atom in ortho (I), meta (III) and para (IV) positions in the benzene ring. The ortho-bromo derivative (II) (C14H13BrN2OS), which is isostructural with its chloro congener (I), is also reported. Mol-ecules (I)-(III) have similar conformations, which approximate to l-shapes, as indicated by their N-C-C-Ct (t = thio-phene) torsion angles of -90.1 (3), -91.44 (18) and -90.7 (9)°, respectively. The conformation of (IV) is different, with an equivalent torsion angle of -170.75 (11)° corresponding to a more extended shape for the mol-ecule. The thio-phene ring in each structure features 'flip' rotational disorder. The packing for (I) and (II) features inversion dimers, linked by pairs of C-H⋯O inter-actions, which generate R22(14) loops. In the crystal of (III), [010] C(8) chains arise, with adjacent mol-ecules linked by pairs of C-H⋯O hydrogen bonds. The packing for (IV) features unusually short C-H⋯O inter-actions arising from an H atom attached to the benzene ring (H⋯O = 2.18 Å), which lead to C(9) [301] chains. Hirshfeld fingerprint percentage contact contributions are similar for the four title compounds.

(+)-Methyl (1R,2S)-2-{[4-(4-Chlorophenyl)-4-hydroxypiperidin-1-yl]methyl}-1-phenylcyclopropanecarboxylate [(+)-MR200] Derivatives as Potent and Selective Sigma Receptor Ligands: Stereochemistry and Pharmacological Properties

Methoxycarbonyl-1-phenyl-2-cyclopropylmethyl based derivatives cis-(+)-1a [cis-(+)-MR200], cis-(-)-1a [cis-(-)-MR201], and trans-(±)-1a [trans-(±)-MR204], have been identified as new potent sigma (σ) receptor ligands. In the present paper, novel enantiomerically pure analogues were synthesized and optimized for their σ receptor affinity and selectivity. Docking studies rationalized the results obtained in the radioligand binding assay. Absolute stereochemistry was unequivocally established by X-ray analysis of precursor trans-(+)-5a as camphorsulfonyl derivative 9. The most promising compound, trans-(+)-1d, showed remarkable selectivity over a panel of more than 15 receptors as well as good chemical and enzymatic stability in human plasma. An in vivo evaluation evidenced that trans-(+)-1d, in contrast to trans-(-)-1d, cis-(+)-1d, or cis-(-)-1d, which behave as σ₁ antagonists, exhibited a σ₁ agonist profile. These data clearly demonstrated that compound trans-(+)-1d, due to its σ₁ agonist activity and favorable receptor selectivity and stability, provided an useful tool for the study of σ₁ receptors.

X-Ray crystallographic and computational study on uranyl-salophen complexes bearing nitro groups

In the solid state, salophen-UO₂ complexes bearing one, two, or three NO₂ groups lack the pronounced ligand curvature that represents a structural hallmark for this class of compounds. A detailed structural study based on single-crystal X-ray crystallography and computational methods, comprising molecular dynamics, gas-phase Hartree Fock, and DFT calculations, was carried out to investigate the coordination properties of the uranyl cation.

Cleavage of Dinitrogen from Forming Gas by a Titanium Molecular System under Ambient Conditions

Simple exposure of a hexane solution of [TiCp*Me₃ ] (Cp*=η⁵ -C₅ Me₅ ) to an atmosphere of commercially available and inexpensive forming gas (H₂ /N₂ mixture, 13.5-16.5 % of H₂ ) at room temperature leads to the methylidene-methylidyne-nitrido cube-type complex [(TiCp*)₄ (μ₃ -CH)(μ₃ -CH₂ )(μ₃ -N)₂ ] via dinitrogen cleavage. This paramagnetic compound reacts with [D₁ ]chloroform to give the titanium(IV) methylidyne-nitrido species [(TiCp*)₄ (μ₃ -CH)₂ (μ₃ -N)₂ ], whereas its one-electron oxidation with AgOTf or [Fe(η⁵ -C₅ H₅ )₂ ](OTf) (OTf=O₃ SCF₃ ) yields the diamagnetic ionic derivative [(TiCp*)₄ (μ₃ -CH)(μ₃ -CH₂ )(μ₃ -N)₂ ](OTf). The μ₃ -nitrido ligands of the methylidyne-nitrido cubane complex can be protonated with [LutH](OTf) (Lut=2,6-lutidine) or hydrogenated with NH₃ ⋅BH₃ to afford μ₃ -NH imido moieties.

Synthesis, structure and properties of imidazolium-based energetic ionic liquids

Energetic ionic liquids bearing a wide liquid temperature range were easily synthesized, which display good thermal stabilities and energetic properties.