Expanding Luminescence Horizons in Macropolyhedral Heteroboranes.

Luminescence is observed in three novel macropolyhedral nineteen- and eighteen-vertex chalcogenaboranes: Se2B17H17 (1), SeB17H19 (3) and SeB18H20 (4). This led us to the recognition that previously published macropolyhedral heteroborane species might also exhibit luminescence. Thus, the known nineteen- and eighteen-vertex dithiaboranes S2B17H17 (2), n-S2B16H16 (5) and i-S2B16H16 (6) were synthesised and also found to exhibit a range of luminescent properties. These macropolyhedral species are very different from the previously unique fluorescent binary borane B18H22 in terms of their structural architectures, by the presence of borane cluster hetero atoms, and, as in the cases of 5 and 6, that their synthetic origins are not derived simply through the modification of B18H22 itself. They consequently greatly expand the possibilities of finding new luminescent inorganic borane species.

Macropolyhedral syn-B18H22, the "Forgotten" Isomer.

The chemistry and physics of macropolyhedral B18H22 clusters have attracted significant attention due to the interesting photophysical properties of anti-B18H22 (blue emission, laser properties) and related potential applications. We have focused our attention on the "forgotten" syn-B18H22 isomer, which has received very little attention since its discovery compared to its anti-B18H22 isomer, presumably because numerous studies have reported this isomer as nonluminescent. In our study, we show that in crystalline form, syn-B18H22 exhibits blue fluorescence and becomes phosphorescent when substituted at various positions on the cluster, associated with peculiar microstructural-dependent effects. This work is a combined theoretical and experimental investigation that includes the synthesis, separation, structural characterization, and first elucidation of the photophysical properties of three different monothiol-substituted cluster isomers, [1-HS-syn-B18H21] 1, [3-HS-syn-B18H21] 3, and [4-HS-syn-B18H21] 4, of which isomers 1 and 4 have been proved to exist in two different polymorphic forms. All of these newly substituted macropolyhedral cluster derivatives (1, 3, and 4) have been fully characterized by NMR spectroscopy, mass spectrometry, single-crystal X-ray diffraction, IR spectroscopy, and luminescence spectroscopy. This study also presents the first report on the mechanochromic shift in the luminescence of a borane cluster and generally enriches the area of rather rare boron-based luminescent materials. In addition, we present the first results proving that they are useful constituents of carbon-free self-assembled monolayers.

Heteroleptic Silver(I) and Gold(I) N-Heterocyclic Carbene Complexes: Structural Characterization, Computational Analysis, Tyrosinase Inhibitory, and Biological Effects.

Derivatization of (NHC)M-Cl (M = Ag, Au) with selected sulfur donors from the family of dialkyldithiophosphates and bis(2-mercapto-1-methylimidazolyl)borate ligands gave a series of heteroleptic mononuclear complexes. In single-crystal X-ray diffraction analysis, Ag(I) complexes adopted a trigonal planar geometry, while Au(I) complexes are near-linear. TD-DFT and hole-electron analyses of the selected complexes gave insight into the electronic features of the metal complexes. In vitro cellular tests were conducted on the human cancerous breast cell line MCF-7 using 2 and 8. The antibacterial activities of complexes 1, 2, 3, 7, 8, and IPr-Ag-Cl were also screened against Gram-positive (Staphylococcus aureus PTCC 1112) and Gram-negative (Escherichia coli PTCC 1330) bacteria. Antityrosinase and hemolytic effects of the selected compounds were also determined.

Introducing Novel Redox-Active Bis(phenolate) N-Heterocyclic Carbene Proligands: Investigation of Their Coordination to Fe(II)/Fe(III) and Their Catalytic Activity in Transfer Hydrogenation of Carbonyl Compounds.

A simple and efficient procedure for synthesizing novel pincer-type tridentate N-heterocyclic carbene bisphenolate ligands is reported. The synthesis of pincer proligands with N,N'-disubstituted imidazoline core, 5 and 6, was carried out via triethylorthoformate-promoted cyclization of either N,N'-bis(2-hydroxy-3,5-di-tert-butylphenyl)cyclohexanediamine, 3, or N,N'-bis(2-hydroxyphenyl)cyclohexanediamine, 4, in the presence of concentrated hydrochloric acid. Cyclic voltammograms of the ligands revealed ligand-centered redox activity, indicating the noninnocent nature of the ligands. The voltammograms of the ligands exhibit two successive one-electron oxidations and two consecutive one-electron reductions. In contrast to previous reports, the redox-active ligands in this study exhibit one-electron oxidation and reduction processes. All products were thoroughly characterized by using 1H and 13C NMR spectroscopy. The base-promoted deprotonation of the proligands and subsequent reaction with iron(II) and iron(III) chlorides yielded compounds 7 and 8. These compounds are binuclear and tetranuclear iron(III) complexes that do not contain carbene functional groups. Complexes 7 and 8 were characterized by using elemental analysis and single-crystal X-ray crystallography. At low catalyst loadings, both 7 and 8 exhibited high catalytic activity in the transfer hydrogenation of selected aldehydes and ketones.

New rac-XP(O)(OC6H5)(NHC6H4-p-CH3) [X = N(CH3)(cyclo-C6H11) and NH(C3H5)] and rac-(C6H5CH2NH)P(O)(OC6H5)(NH-cyclo-C6H11) mixed-amide phosphinates.

The mixed-amide phosphinates, rac-phenyl (N-methylcyclohexylamido)(p-tolylamido)phosphinate, C20H27N2O2P, (I), and rac-phenyl (allylamido)(p-tolylamido)phosphinate, C16H19N2O2P, (II), were synthesized from the racemic phosphorus-chlorine compound (R,S)-(Cl)P(O)(OC6H5)(NHC6H4-p-CH3). Furthermore, the phosphorus-chlorine compound ClP(O)(OC6H5)(NH-cyclo-C6H11) was synthesized for the first time and used for the synthesis of rac-phenyl (benzylamido)(cyclohexylamido)phosphinate, C19H25N2O2P, (III). The strategies for the synthesis of racemic mixed-amide phosphinates are discussed. The P atom in each compound is in a distorted tetrahedral (N(1))P(=O)(O)(N(2)) environment. In (I) and (II), the p-tolylamido substituent makes a longer P-N bond than those involving the N-methylcyclohexylamido and allylamido substituents. In (III), the differences between the P-N bond lengths involving the cyclohexylamido and benzylamido substituents are not significant. In all three structures, the phosphoryl O atom takes part with the N-H unit in hydrogen-bonding interactions, viz. an N-H···O=P hydrogen bond for (I) and (N-H)(N-H)···O=P hydrogen bonds for (II) and (III), building linear arrangements along [001] for (I) and along [010] for (III), and a ladder arrangement along [100] for (II).

Acetonyltriphenyl-phospho-nium nitrate.

Crystals of the title salt, C(21)H(20)OP(+)·NO(3) (-), are composed of acetonyltriphenyl-phospho-nium cations and nitrate anions that mainly inter-act through electrostatic forces. The P atom in the cation has a slightly distorted tetra-hedral environment, with C-P-C angles ranging from 104.79 (7) to 112.59 (6)°. The sum of O-N-O angles of the nitrate anion is 359.99°, reflecting its trigonal-planar character. C-H⋯O hydrogen bonds help to consolidate the crystal packing.

2,2'-{[2-(2-Chloro-phen-yl)-4-methyl-imidazolidine-1,3-di-yl]bis-(methyl-ene)}diphenol.

In the title compound, C24H25ClN2O2, the 2-hy-droxy-benzyl substituents and the 2-chloro-phenyl group occupy the sterically preferred equatorial positions, whereas the methyl group occupies the axial position. The imidazolidine ring adopts an envelope conformation with one of the N atoms adjacent to the methylene group as the flap. The chloro-phenyl substit-uent approaches a nearly perpendicular orientation relative to the mean plane of the imidazolidine ring, making a dihedral angle of 73.44 (12)° and the Cl atom is almost coplanar with the C atom bearing the chloro-phenyl substituent [Cl-C-C-C torsion angle = 1.1 (3)°]. The hy-droxy-benzyl groups make dihedral angles of 71.23 (15) and 69.13 (19)° with the mean plane of the heterocyclic ring. The dihedral angle between the two hy-droxy-benzyl groups is 69.61 (12)°. The mol-ecular structure features two intra-molecular O-H⋯N hydrogen bonds with graph-set motif S(6) between the phenolic hydroxyl groups and N atoms.

2,2'-{[2-(2-Hy-droxy-phen-yl)-4-methyl-imidazolidine-1,3-di-yl]bis-(methyl-ene)}diphenol.

The asymmetric unit in the title compound, C24H26N2O3, comprises two independent mol-ecules (A and B). In molecule A, the central 2-hydroxyphenyl ring is inclined to the mean plane of the major component of the imidazolidine ring by 84.52 (14)°, and by 68.08 (9) and 47.48 (9)° to the outer phenol rings. The later are inclined to one another by 66.76 (9)° and by 78.12 (14) and 80.20 (14)° to the imidazoline ring mean plane. In molecule B, the central 2-hydroxyphenyl ring is inclined to the mean plane of the imidazolidine ring by 73.64 (10)°, and by 75.60 (8) and 38.32 (9)° to the outer phenol rings. The later are inclined to one another by 69.47 (9)° and by 82.60 (10) and 64.26 (10)° to the imidazolidine ring mean plane. In each of the independent mol-ecules, two intra-molecular O-H⋯N hydrogen bond form S(6) ring motifs. In disordered mol-ecule A, the O-H groups of the 2-hy-droxy-benzyl groups are also involved in intra-molecular O-H⋯O hydrogen bonds, with the O atom of the hy-droxy-phenyl group acting as the acceptor. In the crystal, A molecules are linked by pairs of O-H⋯O hydrogen bonds forming inversion dimers. These dimers are linked to the B molecules via O-H⋯O hydrogen bonds forming double-layered slabs lying parallel to the bc plane.

meso-4,4'-Difluoro-2,2'-{[(3aR,7aS)-2,3,3a,4,5,6,7,7a-octa-hydro-1H-1,3-benzimidazole-1,3-di-yl]bis-(methyl-ene)}diphenol.

In the crystal structure of the title compound, C(21)H(24)F(2)N(2)O(2), there are two intra-molecular O-H⋯N hydrogen bonds involving the N atoms of the imidazolidine ring and the hy-droxy groups. The crystal studied was a meso compound obtained by the reaction of the aminal (2S,7R,11S,16R)-1,8,10,17-tetra-aza-penta-cyclo-[8.8.1.1(8,17).0(2,7).0(11,16)]cosane with 4-fluoro-phenol. The imidazolidine ring has a twisted conformation with a CH-CH-N-CH(2) torsion angle of 44.99 (14)° and, surprisingly, the lone pairs of the N atoms are disposed in a syn isomerism, making the title compound an exception to the typical 'rabbit-ear effect' in 1,2-diamines. In the crystal, molecules are linked via C-H⋯F hydrogen bonds, forming chains along the c-axis direction. These chains are linked via another C-H⋯F hydrogen bond, forming a three-dimensional network.

meso-4,4'-Dimeth-oxy-2,2'-{[(3aR,7aS)-2,3,3a,4,5,6,7,7a-octa-hydro-1H-benz-imidazole-1,3-di-yl]bis-(methyl-ene)}diphenol.

The title compound, C23H30N2O4, a di-Mannich base derived from 4-meth-oxy-phenol and cis-1,2-di-amine-cyclo-hexane, has a perhydro-benzimidazolidine nucleus, in which the cyclo-hexane ring adopts a chair conformation and the heterocyclic ring has a half-chair conformation with a C-N-C-C torsion angles of -48.14 (15) and -14.57 (16)°. The mean plane of the heterocycle makes dihedral angles of 86.29 (6) and 78.92 (6)° with the pendant benzene rings. The mol-ecular structure of the title compound shows the presence of two inter-actions between the N atoms of the imidazolidine ring and the hydroxyl groups through intra-molecular O-H⋯N hydrogen bonds with graph-set motif S(6). The unobserved lone pairs of the N atoms are presumed to be disposed in a syn conformation, being only the second example of an exception to the typical 'rabbit-ears' effect in 1,2-di-amines.

Syntheses, crystal structures, Hirshfeld surface analyses and energy frameworks of two 4-amino-anti-pyrine Schiff base compounds: (E)-4-{[4-(di-ethyl-amino)-benzyl-idene]amino}-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one and (E)-4-[(4-fluoro-benzyl-idene)amino]-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one.

The title Schiff base compounds, C22H26N4O (I) and C18H16FN3O (II), were each synthesized by a single-step condensation reaction. The substituted benzyl-idene ring is inclined to the pyrazole ring mean planes by 22.92 (7)° in I and 12.70 (9)° in II. The phenyl ring of the 4-amino-anti-pyrine unit is inclined to the pyrazole ring mean plane by 54.87 (7)° in I and by 60.44 (8)° in II. In the crystal of I, the mol-ecules are linked by C-H⋯O hydrogen bonds and C-H⋯π inter-actions to form layers lying parallel to (001). In the crystal of II, the mol-ecules are linked by C-H⋯O and C-H⋯F hydrogen bonds and C-H⋯π inter-actions, thereby forming layers lying parallel to (010). Hirshfeld surface analysis was employed to further qu-antify the inter-atomic inter-actions in the crystals of both compounds.

Synthesis, crystal structure, cytotoxicity, in-detail experimental and computational CT-DNA interaction studies of 2-picolinate Pd(II) and Pt(II) complexes.

A new Pd(II) complex of formula [Pd(en)(2-pyc)]+ (where, en is ethylenediamine and 2-pyc is 2-pyridinecarboxylate anion) and its reported Pt(II) analogue, i.e. [Pt(en)(2-pyc)]+ have been made by an improved synthetic procedure, yielding above 80%. They have been characterized by FT-IR, UV-Vis, 1H NMR, 13C NMR, conductivity and elemental analysis. Single crystal structural determination of [Pt(en)(2-pyc)]+ displayed that the Pt(II) cation in this complex coordinated by 2-pyc and en each as five member chelate resulting in slightly distorted square-planar array. The time-dependent spectroscopic analysis of these compounds in aqueous medium demonstrated their structural stabilities. The cytotoxic activities of Pd(II) and Pt(II) complexes, free 2-pyc and carboplatin (as standard drug) were assayed in-vitro against the HCT-116 and MCF-7 as cancerous and MCF 10 A and CCD-841 as normal cell lines. They showed the IC50 order of: carboplatin > 2-pyc > Pt(II) > Pd(II) and lower activities against non-cancerous cells. CT-DNA binding of the Pd(II), Pt(II) and 2-pyc free ligand were explored individually. In this relation, UV-Vis and fluorescence titrations disclosed quenching of CT-DNA absorption and emissions by the compounds via dynamic mechanism and formation of H-bonds and van der Waals forces between them. The interaction was further validated and verified by viscosity measurements and gel electrophoresis. Partition coefficient determination showed that all three compounds have more lipophilicity than cisplatin. Furthermore, docking analysis and molecular dynamics simulation were done to evaluate the nature of interaction between aforementioned compounds and CT-DNA. The finding results demonstrated that these agents interact with CT-DNA via groove binding and were in agreement with experimental results.Communicated by Ramaswamy H. Sarma.

Correction to "Homobimetallic Au(I)-Au(I) and Heterotrimetallic Au(I)-Fe(II)-Au(I) Complexes with Dialkyldithiophosphates and Phosphine Ligands: Structural Characterization, DFT Analysis, and Tyrosinase Inhibitory and Biological Effects".

[This corrects the article DOI: 10.1021/acsomega.3c00645.].

Homobimetallic Au(I)-Au(I) and Heterotrimetallic Au(I)-Fe(II)-Au(I) Complexes with Dialkyldithiophosphates and Phosphine Ligands: Structural Characterization, DFT Analysis, and Tyrosinase Inhibitory and Biological Effects.

The role of bridging and terminal ligand electronic and steric properties on the structure and antiproliferative activity of two-coordinated gold(I) complexes was investigated on seven novel binuclear and trinuclear gold(I) complexes synthesized by the reaction of either Au2(dppm)Cl2, Au2(dppe)Cl2, or Au2(dppf)Cl2 with potassium diisopropyldithiophosphate, K[(S-OiPr)2], potassium dicyclohexyldithiophosphate, K[(S-OCy)2], or sodium bis(methimazolyl)borate, Na(S-Mt)2, which afforded air-stable gold(I) complexes. In 1-7, the gold(I) centers adopt a two-coordinated linear geometry and are structurally similar. However, their structural features and antiproliferative properties highly depend upon subtle ligand substituent changes. All complexes were validated by 1H, 13C{1H}, 31P NMR, and IR spectroscopy. The solid-state structures of 1, 2, 3, 6, and 7 were confirmed using single-crystal X-ray diffraction. A density functional theory geometry optimization calculation was used to extract further structural and electronic information. To investigate the possible cytotoxicities of 2, 3, and 7, in vitro cellular tests were carried out on the human cancerous breast cell line MCF-7. 2 and 7 show promising cytotoxicity.

Carborane-thiol protected copper nanoclusters: stimuli-responsive materials with tunable phosphorescence.

Atomically precise nanomaterials with tunable solid-state luminescence attract global interest. In this work, we present a new class of thermally stable isostructural tetranuclear copper nanoclusters (NCs), shortly Cu4@oCBT, Cu4@mCBT and Cu4@ICBT, protected by nearly isomeric carborane thiols: ortho-carborane-9-thiol, meta-carborane-9-thiol and ortho-carborane 12-iodo 9-thiol, respectively. They have a square planar Cu4 core and a butterfly-shaped Cu4S4 staple, which is appended with four respective carboranes. For Cu4@ICBT, strain generated by the bulky iodine substituents on the carboranes makes the Cu4S4 staple flatter in comparison to other clusters. High-resolution electrospray ionization mass spectrometry (HR ESI-MS) and collision energy-dependent fragmentation, along with other spectroscopic and microscopic studies, confirm their molecular structure. Although none of these clusters show any visible luminescence in solution, bright µs-long phosphorescence is observed in their crystalline forms. The Cu4@oCBT and Cu4@mCBT NCs are green emitting with quantum yields (Φ) of 81 and 59%, respectively, whereas Cu4@ICBT is orange emitting with a Φ of 18%. Density functional theory (DFT) calculations reveal the nature of their respective electronic transitions. The green luminescence of Cu4@oCBT and Cu4@mCBT clusters gets shifted to yellow after mechanical grinding, but it is regenerated after exposure to solvent vapour, whereas the orange emission of Cu4@ICBT is not affected by mechanical grinding. Structurally flattened Cu4@ICBT didn't show mechanoresponsive luminescence in contrast to other clusters, having bent Cu4S4 structures. Cu4@oCBT and Cu4@mCBT are thermally stable up to 400 °C. Cu4@oCBT retained green emission even upon heating to 200 °C under ambient conditions, while Cu4@mCBT changed from green to yellow in the same window. This is the first report on structurally flexible carborane thiol appended Cu4 NCs having stimuli-responsive tunable solid-state phosphorescence.

2,2'-[1,2-Phenyl-enebis(aza-nedi-yl)]di-aceto-nitrile.

The title compound, C10H10N4, shows chemical but not crystallographic C2 symmetry. The two cyano-methyl groups are located in an anti position with respect to the aromatic ring. In the crystal, mol-ecules form parallel ladder-like tapes linked through two N-H⋯N hydrogen bonds. Further weak intra-molecular N-H⋯N hydrogen bonding is responsible for the elongation of one of the Caromatic-N bonds.

3,3'-(Ethane-1,2-diyl)bis(6-meth-oxy-3,4-dihydro-2H-1,3-benzoxazine) mono-hydrate.

The asymmetric unit of the title compound, C(20)H(24)N(2)O(4)·H(2)O, contains one half-organic mol-ecule (an inversion centre generates the other half of the mol-ecule) and a half-mol-ecule of water (the O atom has site symmetry 2). The near planarity of the fused-benzene ring is illustrated by the very small deviations of all the atoms from the plane [largest deviation = 0.0092 (11) Å. The six-membered N,O-containing ring adopts a half-chair conformation. The observed N-CH(2) and CH(2)-O bond lengths can be correlated to the manifestation of an anomeric effect in the N-CH(2)-O unit. In the crystal, the mol-ecules are connected into zigzag chains parallel to [001] through O-H⋯N hydrogen bonds formed between the oxazinic N atom and the solvent water mol-ecule. The chains are consolidated by C-H⋯O inter-actions.

4,4'-Difluoro-2,2'-[imidazolidine-1,3-diylbis(methyl-ene)]diphenol.

In the title compound, C(17)H(18)F(2)N(2)O(2), the imidazolidine ring system exists in a twist conformation. The mean plane through this ring system forms dihedral angles of 80.8 (8)° and 66.2 (13)°, with the benzene rings. The dihedral angle between the benzene rings is 52.0 (14)°. Two intra-molecular O-H⋯N hydrogen bonds each generate S(6) ring motifs. In the crystal, weak C-H⋯O hydrogen bonds form dimers, which are connected by further C-H⋯O inter-actions.

4,4'-Dimethyl-2,2'-[imidazolidine-1,3-diylbis(methyl-ene)]diphenol.

The imidazolidine ring in the title compound, C(19)H(24)N(2)O(2), adopts a twist conformation and its mean plane (r.m.s. deviation = 0.19 Å) makes dihedral angles of 72.38 (9) and 71.64 (9)° with the two pendant aromatic rings. The dihedral angle between the phenyl rings is 55.94 (8)°. The mol-ecular structure shows the presence of two intra-molecular O-H⋯N hydrogen bonds between the phenolic hydroxyl groups and N atoms with graph-set motif S(6). In the crystal, C-H⋯O hydrogen bonds lead to the formation of chains along the b-axis direction.

Structure of the high-temperature phase of caesium nitrate - the importance of high-resolution data.

A single-crystal structure determination of the cubic phase of CsNO3 based on data collected at 439 K up to sinθmax/λ = 0.995000 Å-1, i.e. to an unprecedentedly high-θ value, is reported. The structure has been refined in Pm3m (Z = 1). Analysis of the difference electron-density maps revealed that the most appropriate model is the twelve-orientation model with the Cs, N, O1 and O2 atoms situated on the Wyckoff positions 1a, 6f, 6f and 24l, respectively, rather than the eight-orientation aragonite model with the Cs, N and O atoms situated on the Wyckoff positions 1a, 8g and 24m, respectively. Both models, however, show close similarities if the large anisotropic displacement parameters of the O atoms in the eight-orientation aragonite model are taken into account. The reason for this is shown to lie in the smeared electron density around the positions of the disordered [NO3]- anion.