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Molecular knots and links continue to fascinate synthetic chemists. Here, the authors use stacking and hydrogen-bonding interactions between a set of similar building blocks to construct several complex molecular topologies, including a figure-eight knot and a trefoil knot.

The synthesis and characterization of polycarborane-substituted molecules [[Cp*Rh{[E.sub.2][C.sub.2]([B.sub.10][H.sub.10])}].sub.3](tpst) [E = S, Se] are described. Unconventional B[H.sup.[delta]-]-[pyridyl.sup.[delta]+] aromatic hydrogen bonding has enforced the bell-shapes of the molecular units and the Cp* conformations have induced the supramolecular structures.

For the first time, carborane complexes containing a B(4)-S bond were obtained directly by heating mononuclear Pd-B(4)-bound carborane complexes. A possible mechanism involved in sulfur atom migration is presented in which the leaving group, pyridine, benzyl isocyanide or PPh3, is demonstrated to be the trigger of the reaction process. In this work, efficient routes are developed through one-pot reactions to prepare B(4)-S carborane derivatives. [ABSTRACT FROM AUTHOR]

Controlling the dopant type, number, and position in doped metal nanoclusters (nanoparticles) is crucial but challenging. In the work described herein, we successfully achieved the mono-cadmium doping of Au25 nanoclusters, and revealed using X-ray crystallography in combination with theoretical calculations that one of the inner-shell gold atoms of Au25 was replaced by a Cd atom. The doping mode is distinctly different from that of mono-mercury doping, where one of the outer-shell Au atoms was replaced by a Hg atom. Au24Cd is readily transformed to Au24Hg, while the reverse (transformation from Au24Hg to Au24Cd) is forbidden under the investigated conditions. [ABSTRACT FROM AUTHOR]

In modern coordination chemistry, supramolecular coordination complexes take advantage of ligand design to control the shapes and sizes of such architectures. Here we describe how to utilize starting building blocks and a multifunctional ligand to rationally design and synthesize different types of discrete assemblies. Using a hydroxamate ligand featuring two pair of chelating sites together with half-sandwich iridium and rhodium fragments, we were able to construct a series multinuclear organometallic macrocycles and cages through stepwise coordination-driven self-assembly. Experimental observations, supported by computational work, show that selective coordination modes were ascribed to the significant electronic density differences of the two chelating sites, (O,O') and (N,N'). The results underline the advantages of the discrimination between soft and hard binding sites, and suggest that hydroxamic acids can be used as a versatile class of facile multifunctional scaffold for the construction of novel two-dimensional and three-dimensional architectures. [ABSTRACT FROM AUTHOR]

Six tetranuclear half-sandwich iridium and rhodium complexes bridged by neutral N,N'-donor pyridylimine ligands and 1,12-dicarbadodecaborane(12)-1,12-dicarboxylate (p-CDC) were controllably synthesized and fully characterized. The results revealed that the precursors, binuclear complexes [(Cp*M)2{1,4-bis(2-pyridylmethyleneamino)benzene}Cl2][OTf]2 (Cp* = η5-pentamethylcyclopentadienyl, M = Ir (2a), Rh (2b)), have different preferential configurations, and tetranuclear complexes [(Cp*M)4{1,4-bis(2-pyridylmethyleneamino)benzene}2(p-CDC)2][OTf]4 (M = Ir (3a), Rh (3b)), which were prepared using monodentate p-carborane dicarboxylate and 2a or 2b, showed highly twisted backbones. Likewise, homologous regular rectangular compounds [(Cp*M)4{1,4-{(2-C5H4N)HC=N}2-2,3,5,6-Me4C6}2-(p-CDC)2][OTf]4 (M = Ir (4a), Rh (4b)) and [(Cp*M)4{1,4-{(2-C5H4N)HC=N}2-1,5-naphthalene}2(p-CDC)2]-[OTf]4 (M = Ir (5a), Rh (5b)) were obtained following a similar synthetic route. X-ray determination confirmed that 4b and 5b have stacking channels as well. [ABSTRACT FROM AUTHOR]

Organometallic macrocycles based on bridge ligands with terminal imidazole groups show the formation of various patterns. The end imidazolyl finishes the conjugated system on the back bone and can freely twist or rotate just like the joints of a human body such as the knee and wrist. [ABSTRACT FROM AUTHOR]

A series of Cp*Rh-based functional metal-larectangles have been synthesized from metallaligands. Enlargement of one linker leads to the isolation of two novel Borromean link architectures. All these complexes are intact in solution, as evident from ESI-MS spectroscopic analysis. Arising from the combination of open Cu centers and favorable cavity space, }(Cp*Rh)4(bpe)2[Cu-(opba)·2MeOH]2{4(OTf)·6MeOH shows extraordinary catalytic abilities with high efficiency and wide substrate selectivity in the acyl-transfer reaction. [ABSTRACT FROM AUTHOR]

The treatment of binuclear complexes [Cp*2M2(μ-QA)Cl2] (M = Ir, 2a; M = Rh, 2b) (H2QA = 1,4-dihydroxyanthraquinone) with pyrazine or bifuncational pyridyl-based ligands (4,4′-dipyridine (bpy), E-1,2-bis(4-pyridyl)ethene (bpe), 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo), and 2,5-bis(4-pyridyl)-1,3,4-thiadiazol (bpt)) in the presence of AgOTf (OTf = CF3SO3) in CH3OH, gave the corresponding tetra-nuclear complexes, with a general formula of [Cp*4M4(μ-QA)2(μ-L)2](OTf)4(M = Ir, 3a–7a; M = Rh, 3b–7b), respectively. The molecular structure of [Cp*4Ir4(μ-QA)2(μ-pyrazine)2](OTf)4(3a) has been determined by single-crystal X-ray analysis, revealing that the metal centers were connected by pyrazine and bis-bidentate QA2−ligands to construct a rectangular cavity with the dimension of 7.30 × 8.41 × 6.92 Å. Complexes 3aand 3bwere found to exhibit selective trapping of halocarbons properties. [ABSTRACT FROM AUTHOR]

The combination of a ditopic ligand containing a functional “third site” as a bridge and organometallic half-sandwich iridium unit Cp*Ir as the corner leads to the formation of the tetranuclear metallamacrocycle 1, which is reacted with silver compound, resulting in the formation of mixed-metal infinitely tubular coordination network 2. [ABSTRACT FROM AUTHOR]

A series of binuclear half-sandwich p-cymene ruthenium complexes bearing oxamidato ligands [(p-cymene)2Ru2(μ-N,N′-bis(aryl)oxamidato)Cl2] (1–3) was synthesized by the reactions of the lithium salts of oxamide with [(p-cymene)RuCl2]2, respectively. Treatment of the binuclear complexes (1–3) with bidentate ligands such as 4,4′-bipyridine (4,4′-bpy) and trans-1,2-bis(4-pyridyl)ethylene (bpe) in the presence of AgOTf (OTf = CF3SO3) gave the corresponding tetranuclear complexes generally formulated as [(p-cymene)4Ru4(μ-N,N′- bis(aryl)oxamidato)2(μ-4,4′-bpy)2](OTf)4(4a–c) and [(p-cymene)4Ru4(μ-N,N′-bis(aryl)oxamidato)2(μ-bpe)2](OTf)4(5a–c) in high yields. All compounds (1–3, 4a–5c) have been characterized by NMR and IR spectra and elemental analyses. The molecular structures of 1, 4aand 5ahave been determined by single-crystal X-ray analyses. The molecular structures of tetranuclear complexes 4aand 5ashowed that two binuclear fragments as building blocks were connected by 4,4′-bpy or bpe to construct a rectangular cavity with the dimensions 5.57 × 11.28 Å (4a) and 5.56 × 13.65 Å (5a). [ABSTRACT FROM AUTHOR]

Neutral organometallic cyclic tri- and tetra-nuclear halfsandwich iridium complexes 1 and 3, connected with pyridine- 4-thiolato ligands, were synthesized and characterized by X-ray crystallography. [ABSTRACT FROM AUTHOR]

The 16-electron half-sandwich complexes Cp*M[S2C2(B10H10)] (M = Ir (1), Rh (2), Co (3)) react with [Ru(COD)Cl2]xunder basic conditions at 35–40 °C to give different hetero-dinuclear clusters {Cp*M[S2C2(B9H10)]}Ru(COD) (M = Ir (1a), Rh (2a), Co (3a)) and {Cp*M[S2C2(B9H9)]}Ru(COD)(OCH3) (M = Ir (1b), Rh (2b), Co (3b)) with open carborane cages. Moreover, B–H→Ru bridge bonds were observed in complexes 1a, 2a, 3a. In reaction a, minor products trinuclear complex {Cp*Ir[S2C2(B10H10)]}2Ru (1c) and methoxyl-disubstituted complex Cp*Ir[S2C2(B10H8)(OCH3)2] (1d) were successfully isolated. However, when the reaction temperature decreased to 0–10 °C, the kinetically-controlled products, mono-substituted complex Cp*Ir[S2C2(B10H9)(OCH3)] (1e) and disubstituted complex Cp*Ir[S2C2(B10H8)(OCH3)2] (1d), were isolated as the main products; nevertheless, the thermodynamically-controlled products, open-carborane complexes 1aand 1b, were isolated as the minor products. In complex Cp*Co[S2C2(B9H10)]Ru(C7H8) (3c), one COD coordinated to ruthenium has been replaced by toluene. The reactions demonstrate that different types of products can be obtained by controlling the reaction conditions. All these new complexes have been characterized by IR, 1H NMR, 11B NMR and elemental analyses. The molecular structures of 1a, 1b, 1c, 1d, 1e, 2aand 3ahave also been determined by single-crystal X-ray diffraction analyses. [ABSTRACT FROM AUTHOR]

Binuclear complex [Cp* 2Ir 2(μ-CA)Cl 2] ( 2) (CA = chloranilate) was obtained by the reaction of [Cp*IrCl 2] 2( 1) with H 2CA in the presence of base. Treatment of 2with pyridine or 4-(4-bromophenyl)pyridine in the presence of AgOTf (OTf = CF 3SO 3) in CH 3OH gave the corresponding binuclear complexes [Cp* 2Ir 2(μ-CA)(pyridine) 2](OTf) 2( 4a) and [Cp* 2Ir 2(μ-CA){4-(4-bromophenyl) pyridine} 2](OTf) 2( 4b). Reactions of 2with bidentate ligands gave tetranuclear complexes [Cp* 4Ir 4(μ-CA) 2(μ-L) 2](OTf) 4(L = pyrazine, 5a; 4,4′-dipyridyl, 5b; 2,5-bis(4-pyridyl)-1,3,5-oxadiazole, 5c; 1,4-bis(4-pyridyl)benzene, 5d; ( E)-1,2-bis(4-pyridyl)ethene, 5e). X-ray analyses of 5a, 5b, and 5erevealed that each of four Cp*Ir moieties was connected by pyridyl ligands and a bis-bidentate chloranilate (CA) ligand to construct a rectangular cavity with the dimensions 8.03 × 6.92 Å for 5a, 8.03 × 11.24 Å for 5b, and 8.01 × 13.55 Å for 5e. Toluene molecules are contained as solvent molecules in the crystals of 5aand 5b. For 5a, the toluene molecules appeared between the independent rectangles, but the toluene molecules appeared in the rectangle cavity for 5b. The electrochemical properties of 5band 5ewere investigated preliminarily, using cyclic voltammetry. [ABSTRACT FROM AUTHOR]

A 18-electron complex Cp∗IrCl[o-C6H4N(C6H3-Me-p) (CHᆖNC6H3-Me-p)] (Cp∗ = η5-pentamethylcyclopentadienyl) (1a) was obtained by the reaction of the lithium salt of o-C6H4N (C6H3-Me-p)(CHᆖNHC6H3-Me-p) (L1) with [Cp∗IrCl(μ-Cl)]2 in toluene. However, when bulkier ligands (L2 = o-C6H4N(C6H3-Me-p)(CHᆖNHC6H3-i-Me2-2,6), L3 = o-C6H4N(C6H3-Me-p) (CHᆖNHC6H3-i-Pr2-2,6)) were employed in the same reaction, two 16-electron complexes {Cp∗Ir[o-C6H4N(C6H3-Me-p)(CHᆖNC6H3-i-Me2-2,6)]}+Cl− (2b) and {Cp∗Ir[o-C6H4N(C6H3-Me-p)(CHᆖNC6H3-i-Pr2-2,6)]}+Cl− (3b) were formed. A 16-electron complex {Cp∗Ir [o-C6H4N(C6H3-Me-p) (CHᆖNC6H3-Me-p)]}+SO3 CF−3 (1b) bearing L1 could be achieved by the reaction of 1a with AgSO3CF3 in CH3CN solution. The molecular structures of 1a and 2b were determined by X-ray crystallography. Theoretical calculations of all the 18/16-electron species were performed to study their bonding characters and electronic properties. Electron donating effect of Cp∗ and steric effect of anilido-imine ligand were considered as major factors in the formation of coordinative unsaturated complexes 1b, 2b, 3b. [Copyright &y& Elsevier]

The synthesis of trinuclear half-sandwich iridium and rhodium complexes containing both N-heterocyclic carbene (NHC) and 1,2-dicarba-closo-dodecaborane ligands is described. Complexes {Cp*M[E2C2(B10H10)]}3(L) (Cp* = pentamethylcyclopentadienyl; L = tris(2-(3-methylimidazol-2-ylidene)ethyl)amine; M = Ir (7), Rh (8); E = S (a), Se (b)) were obtained from the reactions of Cp*M[E2C2(B10H10)] (M = Ir (3), Rh (4)) with a silver-NHC precursor or from the reactions of [Cp*MCl2]3(L) (M = Ir (5), Rh (6)) with Li2E2C2(B10H10) (E = S, Se). The complexes were characterized by IR, NMR spectroscopy, elemental analysis. In addition, X-ray structure analyses were performed on complexes 7a and 8b. [ABSTRACT FROM AUTHOR]

The reactions of Cp2Ir2(-2-2-C2O4)Cl22aand Cp2Rh2(-2-2-C2O4)Cl22bwith bidentate ligands such as 4,4‘-bipyridine (bpy) and 2,5-bis(4-pyridyl)-1,3,5-oxadiazole (bpo) in the presence of AgOTf gave the corresponding tetranuclear complexes Cp4M4(-L)2(-2-2-C2O4)2(OTf)4(3a:  M Ir, L bpy; 3b:  M Rh, L bpy; 4a:  M Ir, L bpo; 4b:  M Rh, L bpo). The reactions of 2aand 2bwith tridentate ligand 2,4,6-tri(4-pyridyl)-1,3,5-triazine (tpt) in the presence of AgOTf gave the corresponding hexanuclear complexes Cp6M6(-tpt)2(-2-2-C2O4)3(OTf)6(5a:  M Ir; 5b:  M Rh). [ABSTRACT FROM AUTHOR]

A series of new hydroxyindanimine ligands [ArN＝CC2H3(CH3)C6H2(R)OH] (Ar = 2,6-i-Pr2C6H3, R = H (HL1), R = Cl (HL2), and R = Me (HL3)) were synthesized and characterized. Reaction of hydroxyindanimine with Cu(OAc)2 · H2O results in the formation of the mononuclear bis(hydroxyindaniminato)copper(II) complexes Cu[ArN＝CC2H3(CH3)C6H2(R)O]2 (Ar = 2,6-i-Pr2C6H3, R = H (1), R = Cl (2), and R = Me (3)). The complex 2′ was obtained from the chlorobenzene solution of the complex 2, which has the same molecule formula with the complex 2 but it is a polymorph. All copper(II) complexes were characterized by their IR and elemental analyses. In addition, X-ray structure analyses were performed for complexes 1, 2, and 2′. After being activated with methylaluminoxane (MAO), complexes 1–3 can be used as catalysts for the vinyl polymerization of norbornene with moderate catalytic activities. Catalytic activities and the molecular weight of polynorbornene have been investigated for various reaction conditions. [Copyright &y& Elsevier]

Half-sandwich titanium and zirconium complexes with tridentate dianionic aryloxide or arylsulfide ligands R-2-(2-XC6H4)NCHC6H2O2-(XNOR2-, R H, X O (L1); R 4-Me-6-But(R‘), X O (L2); R H, X S (L3); R 4-Me-6-But(R‘), X S (L4)) have been prepared. Reactions of CpMCl3(M Ti, Zr) with sodium salts of the aryloxide or arylsulfide ligands (L1−L4) afford CpTiXNORCl R H, X O (1); R 4-Me-6-But(R‘), X O (2); R H, X S (3); R 4-Me-6-But(R‘), X S (4) and CpZrONORCl R H (5), respectively. Complexes 1−5were characterized by IR and 1H NMR spectra and elemental analyses, and their molecular structures have been determined by X-ray diffraction methods. The coordination properties of these complexes have been investigated in the solid state and compared to related systems. When activated by excess methylaluminoxane (MAO), these complexes can be used as catalysts for ethylene polymerization and exhibited moderate activities. The activities of arylsulfide complexes 3and 4are higher than those of their analogues, aryloxide complexes 1and 2, and zirconium complex 5is much more active than titanium complexes 1−4. [ABSTRACT FROM AUTHOR]

Reaction of carboranyl anion or its thiolate derivative with a fully-substituted Cp*-based group 9 (Ir, Rh) metal complex affords respectively a C-C bond formation complex and a salt metathesis product. This example represents the first nucleophilic addition attempt in the area of M-Cp* chemistry. [ABSTRACT FROM AUTHOR]

An N-heterocycle (pyrazine) utilized as a precursor was employed to construct multinuclear metallamacrocycle 1though C–H activation and metal–metal bond formation under mild conditions. This iridamacrocycle was fully characterized by 1H NMR, IR, and elemental analysis. In order to further confirm its structure, X-ray analysis was carried out, proving the hexanuclear iridium macrocyclic backbone of the complex. [ABSTRACT FROM AUTHOR]

Polycarborane-substituted molecules [Cp*Rh{E2C2(B10H10)}]3(tpst) = S (2a), Se (2b)] were synthesized and characterized. 2a and 2b form toluene solvates in the solid state showing infinitely connected [(2a,b)-(toluene)]∞ helices. The chains of these supramolecules are held together by Cp*-toluene-Cp* π-stacking interactions of two of the three Cp* ligands of the bell-shaped 2a and 2b molecules. Unconventional BHδ--pyridylδ+ aromatic hydrogen bonding enforces the bell-shapes of the molecular units, and the Cp* conformations are expected to induce the supramolecular structures. [ABSTRACT FROM AUTHOR]

Organometallic macrocycles 2a and 2b undergo [2 + 2] photochemical cycloaddition to form 3a and 3b in quantitative yield, accompanied by a single-crystal to single-crystal transformation. [ABSTRACT FROM AUTHOR]

Octanuclear complexes with half-sandwich Ir, Rh and Ru fragments and tetra(4-pyridyl)porphyrin (L1) and oxalate (L2) spacer ligands [(Cp*M)4L1]2[L2]4 (M = Ir (6a) M = Rh (6b)), [((cymene)Ru)4(L1)]2[L2]4 were prepared and characterized. [ABSTRACT FROM AUTHOR]

Morpholine and methylpiperazine are among the most important structural parts of different drugs including organic chemotherapeutic agents. In the current study we incorporated these entities as co-ligand and a series of structurally related mono- and di-metallic square planner Pt(II) complexes (Pt(II)(salicylaldimine)(morpholine)Cl C1a-C3a, Pt(II)(salicylaldimine) (methylpiperazine)Cl C1b-C3b, di-metallic Pt(II)2(bis-salicylaldimine)(morpholine)2Cl2C4a and Pt(II)2(bis-salicylaldimine)(methylpiperazine)2Cl2C4b were prepared. These complexes were characterized by ¹H, 13C, 19F, 2D NOESY NMR, HR ESI-MS and elemental analyses, while structures of C2a, C3a and C4b were determined by single crystal X-ray analysis. All these complexes were studied for their in vitro cytotoxic effect on breast (MCF-7), liver (HepG2) and lung (A549) cancer cell lines. All these complexes showed considerable cytotoxic effect on these tested cancer cell lines comparable to cisplatin. Moreover three complexes C1a, C4a and C1b were studied in details. Time- and dose-dependent study was performed for C1a, C4a and C1b. These complexes induced the expression of p53 that suppresses cancer cell growth. Induction of PUMA gene and repression of MYC oncogene suggested that these complexes targeted different genes to suppress cancer progression. TUNEL assay showed induction of apoptosis and invasion analysis showed reduction in invasion ability of breast cancer cells treated with C1a, C4a or C1b. Importantly, these novel complexes suppressed the expression of EMT and metastasis promoter genes. Similarly these complexes induced autophagy by enhancing the expression of autophagy related genes such as beclin, atg-5 and atg-7. The E. coli growth retardation study showed stronger growth inhibitory effects and subsequently resulted in filamentous morphology of bacterial cells. Gel electrophoresis study proved the interaction of these complexes with DNA. All these analysis revealed anticancer potencies of this class of complexes. [ABSTRACT FROM AUTHOR]