Sterically Encumbered Sb (III) Selone Complex: Synthesis, Characterization and Photophysical Study

An antimony (III) selone complex was synthesized starting from the corresponding imidazole selone IPr*Se. This newly isolated Sb (III) complex was fully characterized by NMR, FT-IR, TGA and single crystal X-ray diffraction techniques. In a solid state structure the IPr*Se depicts a rare coordination mode. The molecule is a neutral binuclear antimony (III) selone with Sb:Se ratio of 2:1. Notably the Sb-Se bond length is slightly longer than expected, due to the sterically superbulky ligand. Besides the Sb---π aryl interactions was observed in the molecular packing. The antimony (III) selone represents the first example of metal selone reported with unusual coordination mode of imidazole selone. In addition, the photophysical properties of IPr*=Se and antimony (III) selone were investigated and compared

A Sustainable Approach for Graphene Oxide‐supported Metal N‐ Heterocyclic Carbenes Catalysts

Sustainable noble metal-N-heterocyclic carbenes (NHC's) are a topic of arising concern in both the chemical industry and the academic community due to a growing consciousness of environmental pollution and scarcity. Recovering and reusing homogeneous catalysts from the reaction mixture requires a tremendous amount of capital investment in the chemical manufacturing industry. Heterogeneous catalysts are proved to have better functional groups tolerance; however, catalysts support largely influences the active catalyst sites to affect catalyst efficiency and selectivity. Thus the, choice of catalyst supports plays an almost decisive role in this emerging area of catalysis research. Graphene oxide (GO)/reduced graphene oxide (rGO) support has a potential growth in heterogeneous catalysis owing to their commercial availability, considerably larger surface area, inert towards chemical transformations, and easy surface functionalization to attached metal complexes via covalent and non-covalent aromatic π-conjugates. To take advantage of two independently well-established research areas of noble metal-N-heterocyclic carbenes and GO/rGO support via covalent or non-covalent interactions approach would offer novel heterogeneous complexes with improved catalytic efficiency without sacrificing product selectivity. This unique concept of marrying metal-N-heterocyclic carbenes with GO/rGO support has potential growth in the chemical and pharmaceutical industry, however, limited examples are reported in the literature. In this perspective, a comprehensive summary of metal−NHC synthesis on GO/rGO support and synthetic strategies to graft M−NHC onto GO/rGO surface, catalytic efficiency, for the catalytic transformation are critically reviewed. Furthermore, a plausible mechanism for non-covalent grafting methodology is summarized to direct readers to give a better understanding of M−NHC@rGO complexes. This would also allow the designing of engineered catalysts for unexplored catalytic applications

Highly Active Cyclic Zinc(II) Thione Catalyst for C−C and C−N Bond Formation Reactions

The first discrete seven-membered cyclic zinc(II) complex catalyzed room temperature Knoevenagel condensation reactions, and the synthesis of perimidine derivatives has been reported under mild reaction conditions. The cyclic zinc(II) complex [(L)ZnBr2] (1) was isolated from the reaction between 1-(2-hydroxyethyl)-3-isopropyl-benzimidazol-2-thione (L) and ZnBr2. Complex 1 was characterized by different analytic techniques such as FT-IR, CHNS, TGA, NMR, and SCXRD. The mononuclear zinc(II) complex 1 was utilized as a catalyst for Knoevenagel condensation reactions to isolate twenty different substituted methylene malononitriles with excellent yield. Besides, the zinc(II) thione complex 1 was utilized for the synthesis of 2,4-dihydroperimidine derivatives in a highly efficient manner. Catalyst 1 depicted wide substrate scopes. Overall, twenty different substituted methylene malononitriles and nine different perimidine derivatives were synthesized using catalyst 1 at room temperature. The present investigation features a mild and fast synthetic approach along with excellent functional group tolerance

Super bulky Bismuth(III) imidazole selones

Treatment of BiBr3 with super bulky [(IPaul)Se] (L1) ([(IPaul)Se] = 1,3-bis(2,4-methyl-6-diphenyl phenyl)imidazole selone) or IPr*Se (L2) (IPr*Se = 1,3-bis(2,6-diphenylmethylphenyl)imidazole selone) in toluene afforded the dinuclear complex [(L1)BiBr2(µ-Br)]2 (1) and mononuclear complex [(L2)BiBr3] (2), whose structures have been determined by an X-ray crystallographic study. The complexes were characterized by a combination of 1H NMR and 13C{1H} NMR spectroscopy. The thermal stability of 1 and 2 was compared using TGA. The steric controlled super bulky ligand systems allow for the first structural isolation of a novel super bulky dinuclear complex 1 with edge shared octahedral geometry and mononuclear super bulky complex 2 with mono capped seesaw geometry. The sterically more crowded complex 2 showed the long Bi-Se bond distance (3.192(3) Å) compared to 1 (2.902(5) Å)

Antimony(III)-selenium complexes with synergetic effect between Sb-Se bond and Sb center dot center dot center dot pi interactions

The imidazole-selone antimony(III) complexes have been described with unique bonding situations around the antimony center. The mononuclear complexes, (L-1)SbCl3 (1) and (L-2)SbCl3 (2) were isolated from the reaction between SbCl3 and corresponding symmetrically crowded, 1,3-bis(2,6-diisopropyl phenyl) imidazole selone (L-1) and unsymmetrically crowded, 2,(2,6-benzhydryl-4-methyl phenyl) imidazole pyridine selone (L-2), respectively. The bonding nature of 1 and 2 differ remarkably due to the unique steric hindrance around the antimony center. Besides, the lone-pair-pi-hole interaction was observed in 1 and 2. The extent of Se -{\textgreater} Sb bonding and (aryl)C -{\textgreater} Sb bonding were further investigated by density functional theory (DFT), including natural bond orbital (NBO), natural population analysis (NPA), and electron density difference (EDD) methods. The theoretical predictions are nearly convincing with a single crystal X-ray analysis. The increasing steric bulk of the imidazole-selone from symmetric to unsymmetrical nature was found to greatly influence the donor-acceptor magnitude of Se -{\textgreater} Sb bonding and (aryl)C -{\textgreater} Sb bonding and lone-pair-pi-hole interactions. The L-2 in 2 acts as a good sigma-donor and pi-donor to Sb(III) compare to L-1 in 1

Rare antimony(iii) imidazole selone complexes: steric controlled structural and bonding aspects

Novel antimony(iii) imidazole selone complexes in a super crowded environment are reported for the first time. The super bulky selone antimony complexes, [{IPr∗Se}(SbCl3)2] (1) and [{IPr∗Se}(SbBr3)2] (2), were isolated from the reactions between IPr∗Se (IPr∗Se = [1,3-bis(2,6-diphenylmethylphenyl)imidazole selone]) and suitable antimony(iii) halides. 1 and 2 are dinuclear complexes with a Sb:Se ratio of 1:0.5 with an unusual coordination mode of selone. The molecules 1 and 2 consist of both Menshutkin-type Sb⋯πaryl interactions and a Sb-Se coordination bond. However, the reaction between antimony(iii) halides and [(IPaul)Se] ([(IPaul)Se] = [1,3-bis(2,4-methyl-6-diphenyl phenyl)imidazole selone]) with a spatially defined steric impact gave the dinuclear complex [{(IPaul)Se}(SbCl3)]2 (3) and the mononuclear complex [{(IPaul)Se}(SbBr3)] (4) without Menshutkin-type interactions. The Sb:Se ratio in 3 and 4 is 1:1. Interestingly, the Menshutkin-type interaction was absent in 3 and 4 due to the efficient coordinating ability of the ligand [(IPaul)Se] with the Sb(iii) center compared to that of the super bulky ligand IPr∗Se. The thermal property of these antimony selone complexes was also investigated. Density functional theory (DFT) calculations were carried out on the model systems [L(SbCl3)2] (1A), [L(SbCl3)] (1B), [L′(SbCl3)2] (1C), and [L′(SbCl3)] (1D), where L = [1,3-bis(2,6-diisopropyl-4-methyl phenyl)imidazole selone] and L′ = [1,3-bis(phenyl)imidazole selone], to understand the nature of orbitals and bonding situations. The computed metrical parameters of 1A are in good agreement with the experimental values. Natural population analysis of the model system reveals that the natural charge and total population of antimony(iii) are comparable. The unequal interaction between selenium and antimony obtained using Wiberg bond indices (WBIs) is fully consistent with the findings of the single-crystal X-ray studies

Dinuclear complexes, a one dimensional chain and a two dimensional layer of bismuth(iii) chalcogenones for C–S cross coupling reactions

The catalytic application of bismuth(iii) coordination polymers has been reported. Dinuclear bismuth(iii) chalcogenone complexes, namely, [(L1)2BiCl2(μ2-Cl)]2 (1), [(L2)2BiBr2(μ2-Br)]2 (4), a 2D layered bismuth(iii) thione complex [{(L2)BiCl2(μ2-Cl)}2]∞ (2), and 1D chain [(L1)Bi(Br)(μ2-Br)2·CH3CN]∞ (3), were isolated by treating the corresponding chalcogenone ligands [1-(2-hydroxyethyl)-3-isopropyl-1H-benzo[d]imidazole-2(3H)-selone (L1) and 1-(2-hydroxyethyl)-3-isopropyl-1H-benzo[d]imidazole-2(3H)-thione (L2)] with BiX3 (X = Cl, Br). Complexes 1-4 were characterized by FTIR and NMR spectroscopy, CHNS analysis, and single-crystal X-ray diffraction techniques. Besides, complexes 1-4 were utilized as catalysts in C-S cross-coupling reactions. Catalysts 1-4 were highly active. Interestingly, the 1D coordination polymer 3 displayed superior catalytic efficiency to discrete complexes 1 and 4 and the thione-based 2D coordination layer 2. The scope of the catalytic reaction was demonstrated using catalyst 3 for annulated heterocyclic aryl halides such as 9-chloro acridine and gave excellent yields. © 2022 The Royal Society of Chemistr

LnIII (Ln = La, Gd, and Dy) Benzimidazolium Tricarboxylate Coordination Polymers with Hydrogen Bonding Modulated Magnetic Relaxation

The novel LnIII {Ln = Dy (1_Dy), Gd (2_Gd), and La (3_La)} benzimidazolium tricarboxylate coordination polymers have been synthesized, and their magnetic properties have been investigated. Single-crystal X-ray analysis revealed that 1_Dy, 2_Gd, and 3_La are one-dimensional coordination polymers with general molecular formulas of {[Ln(L)2(H2O)4]center dot(6Br)}infinity [L = 3,3 ',3 ''-((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene))tris(1-(carboxymethyl)-benzimidazolium)], which crystallized in the monoclinic, P21/c space group. The solid-state packing of these coordination polymers shows the spiral propagation in a one-dimensional direction. The direct current (dc) magnetic data (susceptibility and magnetization) were collected for 1_Dy and 2_Gd. The alternating current (ac) magnetic measurement for 1_Dy at zero field shows the characteristic signature of single-molecule magnets (SMMs) at low temperatures but without clear maxima. Further, to rationalize the experimentally observed magnetic behavior and to understand the factors affecting the dynamic magnetic behavior of 1_Dy, we performed detailed completed active space self-consistent field (CASSCF) based calculations on 1_Dy. Our detailed theoretical analysis suggests that the hydrogen bonding interaction between the coordinated water molecule and the Br- counteranion increases the equatorial electron density, eradicating the slow relaxation in 1_Dy

Acridine N ‐Heterocyclic Carbene Gold(I) Compounds: Tuning from Yellow to Blue Luminescence

The synthesis and the luminescence features of three gold(I)-N-heterocyclic carbene (NHC) complexes are presented to study how the n-alkyl group can influence the luminescence properties in the crystalline state. The mononuclear gold(I)-NHC complexes, [(L1)Au(Cl)] (1), [(L2)Au(Cl)] (2), and [(L3)Au(Cl)] (3) were isolated from the reactions between [(tht)AuCl] and corresponding NHC ligand precursors, [N-(9-acridinyl)-N’-(n-butyl)-imidazolium chloride, (L1.HCl)], [N-(9-acridinyl)-N’-(n-pentyl)-imidazolium chloride, (L2.HCl)] and [N-(9-acridinyl)-N’-(n-hexyl)-imidazolium chloride, (L3.HCl)]. Their single-crystal X-ray analysis reveals the influence of the n-alkyl groups on solid-state packing. A comparison of the luminescence features of 1–3 with n-alkyl substituents is explored. The molecules 1–3 depicted blue emission in the solution state, while the yellow emission (for 1), greenish-yellow emission (for 2), and blue emission (for 3) in the crystalline phase. This paradigm emission shift arises from n-butyl to n-pentyl and n-hexyl in the crystalline state due to the carbon-carbon rotation of the n-alkyl group, which tends to promote unusual solid packing. Hence n-alkyl group adds a novel emission property in the crystalline state. Density Functional Theory and Time-Dependent Density Functional Theory calculations were carried out for monomeric complex, N-(9-acridinyl)-N’-(n-heptyl)imidazole-2-ylidene gold(I) chloride and dimeric complex, N-(9-acridinyl)-N’-(n-heptyl)imidazole-2-ylidene gold(I) chloride to understand the structural and electronic properties