Dinuclear Silver（Ⅰ） Complex Based on 1-Picolyl-3-propylbenzimidazolium Salt： Crystal Structure and Weak Interactions

1-Picolyl-3-propylbenzimidazolium bromide (LBr) was prepared from benzimida- zole by alkylation with 2-chloromethyl-pyridine in the presence of NaH, followed by quaternization with 1-bromopropane. Ligand LBr was treated with AgBr in CH2Cl2 to afford a dinuclear silver(I) complex L2Ag2Br4 (1). In complex 1, a 2-D supramolecular layer is formed through two types of π-π stacking interactions. Fluorescent emission spectra of ligand LBr and complex 1 are described.     

Synthesis,crystal structures,and characterization of copper(II) carboxylate complexes incorporating 1,10-phenanthroline and bipyridine

A series of Cu(II) carboxylate complexes (carboxylate?=?2-fluorobenzoic acid (2-HFBA) or 4-fluorobenzoic acid (4-HFBA)) containing either one chelating 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy) have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, and thermal analyses. In [Cu(bipy)(H₂O)(2-FBA)₂] (1), [Cu(bipy)(H₂O)(4-FBA)₂] (3), and [Cu(phen)(H₂O)(2-FBA)₂] (4), Cu is five-coordinate in a square pyramidal geometry and four-coordinate in [Cu(phen)(2-FBA)₂] (2). The four complexes are extended into 1-D chains through hydrogen-bonding and π?···?π interactions in 1 and 4, only hydrogen-bonding in 2, and π?···?π interactions in 3. These contacts lead to aggregation and supramolecular self-assembly.     

A Novel Supramolecular Structure for a Lanthanum Picrate

A new complex of lanthanum picrate with N,N'-diethyl-N,N'-diphennyl-3-oxapentanediamide (L) was synthesized and its structure determined by X-ray diffraction measurements. It crystallizes as the ten-coordinate complex La(pic)₃L₂ in the triclinic space group P1 with a = 12.140(2), b = 14.250(2), c = 20.333(2) Å, α = 101.400(10), β = 99.390(10), γ = 102.400(10)°, U = 3289.1(8) ų, Z = 2, D_c = 1.519 g cm^-3. The complex possesses a novel ladder-like 2-D supramolecular structure directed by π-π interactions.     

Cyclometallated complexes derived from pyrimidin- and pyridazinehydrazones: Structural evidence of intermolecular “chelate metal ring” π-π interactions

Reaction of 3,4-(Me)₂C₆H₃C(Me)NN(H)[3′-(CF₃)C₄H₂N₂] (a) and 3,4-(Me)₂C₆H₃C(Me)NN(H)(4′-ClC₄H₂N₂) (b) with palladium(II) acetate gave the mononuclear cyclometallated complexes [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}(OAc)] (1a) and [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)}(OAc)] (1b) with the ligand as terdentate [C,N,N]. Treatment of a and b with Li₂[PdCl₄] and sodium acetate in methanol at room temperature yielded the mononuclear cyclometallated complexes [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}(Cl)] (2a) and [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)}(Cl)] (2b), respectively. Recrystallization of 2b from a dimethylsulfoxide solution gave [Pd{3,4-(Me)₂C₆H₂C(Me)NN(4′-ClC₄H₂N₂)}][(CH₃)₂SO] after deprotonation of the hydrazine nitrogen. The reaction of 2a and 2b with silver trifluoromethanesulfonate and triphenylphosphine, yielded [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}-(PPh₃)][CF₃SO₃] (3a) and [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)}(PPh₃)]-[CF₃SO₃] (3b) with the phosphine ligand occupying the vacant coordination position after chlorine abstraction; these were deprotonated at the hydrazine nitrogen after treatment with sodium acetate. Reaction of 2a with Ph₂P(CH₂)₂AsPh₂ (arphos), after AgCl removal gave mononuclear complex Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}(Ph₂P(CH₂)₂AsPh₂)][ClO₄] (5a) with a non-coordinated As atom. Reaction of 2a and 2b with a Ag(I) salt and the tertiary diphosphine Ph₂P(CH₂)₄PPh₂ (dppb) in 2:1 molar ratio gave the dinuclear complexes [{Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}}₂(μ-Ph₂P(CH₂)₄PPh₂)][CF₃SO₃]₂ (6a) and [{Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)}}₂(μ-Ph₂P(CH₂)₄PPh₂)][ClO₄]₂ (6b) with the diphosphine as a bridging ligand. Similarly, treatment of 1b with silver triflate followed by reaction with the tertiary triphosphine (Ph₂PCH₂CH₂)₂PPh (triphos), in a 3:1 molar ratio, gave the new trinuclear complex [{Pd[3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)]}₃{μ₃-(Ph₂PCH₂CH₂)₂PPh}][CF₃SO₃]₃ (8b). However, reaction of 2a and 2b with (triphos), in 1:1 molar ratio gave the mononuclear complexes [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}{(Ph₂PCH₂CH₂)₂PPh-P,P,P}][ClO₄] (7a) and [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)}-{(Ph₂PCH₂CH₂)₂PPh-P,P,P}][ClO₄] (7b) with a is five-coordinated palladium. The crystal structures of 2b, 3a, 3b, 7a and 7a have been determined by X-ray crystallography and they show π-π interactions between the metallacycle and the heterocyclic pyrimidine or pyridazine rings, which controls the crystal packing.     

Synthesis,crystal structures and luminescent properties of phenylmercury(II) complexes with thiohydrazone ligands having weak Hg····π and Hg····Hg interactions

The Reaction of phenylmercury(II) acetate with salicylaldehyde morpholine N-thiohydrazone (H₂smth) and 2-hydroxyacetophenone morpholine N-thiohydrazone (H₂apmth) in dry ethanol under gentle refluxing condition form light yellow complexes [PhHg(Hsmth)] (1) and [PhHg(Hapmth)] (2) involving formation of Hg-S bond from the thiol form of the ligands after deprotonation of the SH proton. The structures of the complexes as determined by X-ray crystallography shows that the complex (1) has a distorted T-shaped geometry while the complex (2) adopts familiar linear coordination geometry. Complex (2) has two independent molecules comprising the asymmetric unit. Both the complexes form two-dimensional supramolecular assemblies due to a combination of weak intermolecular Hg····π and Hg····Hg interactions. The Hg····π and Hg····Hg distances are 3.937 and 4.0216(10) Å, respectively, possibly indicating weak mercuriophilic interactions. The luminescent properties of the complexes in solution and in the solid state at room temperature are also described.     

Synthesis, X-ray crystallographic, and dynamic H NMR studies of crown-tetrathia[3.3.3.3]metacyclophanes—conformational control by cooperative intramolecular C-H?π interaction both in solid state and in solution

Crown-tetrathia[3.3.3.3]metacyclophanes 3a-c were synthesized via intermolcular coupling reaction in 22-30% yields. X-ray crystal analysis of 3b revealed that it adopted a perpendicular conformation (3b-B or 3b-C) in which two aromatic rings were inclined to be perpendicular to the opposite aromatic rings, driving two internal methyl groups into the π-cloud of the corresponding benzene rings. Furthermore, this perpendicular structural feature led to benzylic protons of thia-bridges being in close proximity to the adjacent aromatic rings. As a result, the induced upfield shifts for the two internal methyl protons and four benzylic protons were clearly observed in dynamic ¹H NMR spectra at low temperature, indicating that the intramolecular C-H?π interaction became increasingly important at low temperature. The energy barrier for inter-conversion between 3b-B and 3b-C was estimated to be 12.1 kcal mol⁻¹ by using a coalescence method. The total stabilization enthalpy of the C-H?π interactions was quantitatively calculated to be 7.9±0.8 kcal mol⁻¹ by the dynamic NMR spectroscopy. In contrast, 3a showed two non-interconvertible conformers at room temperature, which tended to interconvert at elevated temperature, however, many conformers co-existed at low temperature.     

Synthesis and Crystal Structure of Dichlorobis(1-methylimidazoline-2(3H)-thione-S) Cobalt(II)

The reaction of anhydrous cobalt(II) dichloride with 1-methylimidazoline-2(3H)thione in dichloromethane solution gave the title complex, [Co(C4H6N2S)2Cl2]. X-ray single-crystal analysis revealed that the complex crystallizes in a monoclinic system, space group P21/c, a = 13.9707(10), b = 10.0435(7), c = 10.3910(6) (A), β = 91.181(3)o, V = 1457.70(17) (A)3, Z = 4, C8H12Cl2N4S2Co, Mr = 358.17, Dc = 1.632 g/cm3, μ = 1.813 mm-1, F(000) = 724, the final R = 0.0710 and wR = 0.1224 for 1549 observed reflections with I > 2((I). The Co atom is coordinated by two S atoms from two 1-methylimidazoline-2(3H)-thione ligands and two chloride ions in a slightly distorted tetrahedral geometry. The intramolecular classical hydrogen-bonding interactions involving chloride ions and N-H groups of the heterocyclic thione ligands are observed. The offset π-π stacking interactions between the imidazole rings of adjacent molecules with a face-to-face distance of 3.604 (A) are found in the packing diagram.     

Tl2D coordination polymer involving close Tl?π (aromatic) contacts, [Tl3(μ-BPC)2(μ-NO3)]n

A two-dimensional polymer, [Tl₃(μ-BPC)₂(μ-NO₃)]_n [BPC = biphenyl-2-carboxylate], has been synthesized and characterized. Its single-crystal X-ray structure shows three types of Tl^I-ions with coordination numbers of 5 (Tl1 and Tl2), and 4 (Tl3). Two of the thallium atoms, Tl1 and Tl3, contain close Tl^I?π (aromatic) contacts, thus attaining a total hapticity of 11 and 10 with environments Tl1O₅C₆ and Tl3O₄C₆, respectively.     

Experimental Quantification of Halogen⋅⋅⋅Arene van der Waals Contacts

Crystallographic and computational studies suggest the occurrence of favourable interactions between polarizable arenes and halogen atoms. However, the systematic experimental quantification of halogen⋅⋅⋅arene interactions in solution has been hindered by the large variance in the steric demands of the halogens. Here we have synthesized molecular balances to quantify halogen⋅⋅⋅arene contacts in 17 solvents and solvent mixtures using ¹H NMR spectroscopy. Calculations indicate that favourable halogen⋅⋅⋅arene interactions arise from London dispersion in the gas phase. In contrast, comparison of our experimental measurements with partitioned SAPT0 energies indicate that dispersion is sufficiently attenuated by the solvent that the halogen⋅⋅⋅arene interaction trend was instead aligned with increasing exchange repulsion as the halogen increased in size (ΔG_X⋅⋅⋅_Ph=0 to +1.5 kJ mol⁻¹). Halogen⋅⋅⋅arene contacts were slightly less disfavoured in solvents with higher solvophobicities and lower polarizabilities, but strikingly, were always less favoured than CH₃⋅⋅⋅arene contacts (ΔG_Me⋅⋅⋅_Ph=0 to −1.4 kJ mol⁻¹).