Two nickel(II) bis[(pyridin‐2‐yl)methyl]amine complexes with homophthalic and benzene‐1,2,4,5‐tetracarboxylic acids

Two new Ni^II complexes involving the ancillary ligand bis[(pyridin‐2‐yl)methyl]amine (bpma) and two different carboxylate ligands, i.e. homophthalate [hph; systematic name: 2‐(2‐carboxylatophenyl)acetate] and benzene‐1,2,4,5‐tetracarboxylate (btc), namely catena‐poly[[aqua{bis[(pyridin‐2‐yl)methyl]amine‐κ³N,N′,N′′}nickel(II)]‐μ‐2‐(2‐carboxylatophenyl)aceteto‐κ²O:O′], [Ni(C₉H₆O₄)(C₁₂H₁₃N₃)(H₂O)]_n, and (μ‐benzene‐1,2,4,5‐tetracarboxylato‐κ⁴O¹,O²:O⁴,O⁵)bis(aqua{bis[(pyridin‐2‐yl)methyl]amine‐κ³N,N′,N′′}nickel(II)) bis(triaqua{bis[(pyridin‐2‐yl)methyl]amine‐κ³N,N′,N′′}nickel(II)) benzene‐1,2,4,5‐tetracarboxylate hexahydrate, [Ni₂(C₁₀H₂O₈)(C₁₂H₁₃N₃)₂(H₂O)₂]·[Ni(C₁₂H₁₃N₃)(H₂O)₃]₂(C₁₀H₂O₈)·6H₂O, (II), are presented. Compound (I) is a one‐dimensional polymer with hph acting as a bridging ligand and with the chains linked by weak C—H...O interactions. The structure of compound (II) is much more complex, with two independent Ni^II centres having different environments, one of them as part of centrosymmetric [Ni(bpma)(H₂O)]₂(btc) dinuclear complexes and the other in mononuclear [Ni(bpma)(H₂O)₃]²⁺ cations which (in a 2:1 ratio) provide charge balance for btc⁴⁻ anions. A profuse hydrogen‐bonding scheme, where both coordinated and crystal water molecules play a crucial role, provides the supramolecular linkage of the different groups.     

Structural studies of (prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine hetero‐scorpionate copper complexes

The structures of five compounds consisting of (prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine complexed with copper in both the Cu^I and Cu^II oxidation states are presented, namely chlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(I) 0.18‐hydrate, [CuCl(C₁₅H₁₇N₃)]·0.18H₂O, (1), catena‐poly[[copper(I)‐μ₂‐(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ⁵N,N′,N′′:C²,C³] perchlorate acetonitrile monosolvate], {[Cu(C₁₅H₁₇N₃)]ClO₄·CH₃CN}_n, (2), dichlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II) dichloromethane monosolvate, [CuCl₂(C₁₅H₁₇N₃)]·CH₂Cl₂, (3), chlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II) perchlorate, [CuCl(C₁₅H₁₇N₃)]ClO₄, (4), and di‐μ‐chlorido‐bis({(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II)) bis(tetraphenylborate), [Cu₂Cl₂(C₁₅H₁₇N₃)₂][(C₆H₅)₄B]₂, (5). Systematic variation of the anion from a coordinating chloride to a noncoordinating perchlorate for two Cu^I complexes results in either a discrete molecular species, as in (1), or a one‐dimensional chain structure, as in (2). In complex (1), there are two crystallographically independent molecules in the asymmetric unit. Complex (2) consists of the Cu^I atom coordinated by the amine and pyridyl N atoms of one ligand and by the vinyl moiety of another unit related by the crystallographic screw axis, yielding a one‐dimensional chain parallel to the crystallographic b axis. Three complexes with Cu^II show that varying the anion composition from two chlorides, to a chloride and a perchlorate to a chloride and a tetraphenylborate results in discrete molecular species, as in (3) and (4), or a bridged bis‐μ‐chlorido complex, as in (5). Complex (3) shows two strongly bound Cl atoms, while complex (4) has one strongly bound Cl atom and a weaker coordination by one perchlorate O atom. The large noncoordinating tetraphenylborate anion in complex (5) results in the core‐bridged Cu₂Cl₂ moiety.     

An unusual partial occupancy of labile chloride and aqua ligands in cocrystallized isomers of a nickel(II) complex bearing a tripodal N4‐donor ligand

A novel Ni²⁺ complex with the N₄‐donor tripodal ligand bis[(1‐methyl‐1H‐imidazol‐2‐yl)methyl][2‐(pyridin‐2‐yl)ethyl]amine (L), namely, aqua{bis[(1‐methyl‐1H‐imidazol‐2‐yl‐κN³)methyl][2‐(pyridin‐2‐yl‐κN)ethyl]amine‐κN}chloridonickel(II) perchlorate, [NiCl(C₁₇H₂₂N₆)(H₂O)]ClO₄ or [NiCl(H₂O)(L)Cl]ClO₄ ( 1 ), was synthesized and characterized by spectroscopic and spectrometric methods. The crystal structure of 1 reveals an interesting and unusual cocrystallization of isomeric complexes, which are crystallographically disordered with partial occupancy of the labile cis aqua and chloride ligands. The Ni²⁺ centre exhibits a distorted octahedral environment, with similar bond lengths for the two Ni—N(imidazole) bonds. The bond length increases for Ni—N(pyridine) and Ni—N(amine), which is in agreement with literature examples. The bond lengths of the disordered labile sites are also in the expected range and the Ni—Cl and Ni—O bond lengths are comparable with similar compounds. The electronic, redox and solution stability behaviour of 1 were also evaluated, and the data obtained suggest the maintenance of structural integrity, with no sign of demetalation or decomposition under the studied conditions.     

Structural and spectroscopic characterization of two new blue luminescent pyridylbenzimidazole zinc(II) complexes

Luminescent metal complexes are used in photooptical devices. Zinc(II) complexes are of interest because of the ability to tune their color, their high thermal stability and their favorable carrier transport character. In particular, some zinc(II) complexes with aryl diimine and/or heterocyclic ligands have been shown to emit brightly in the blue region of the spectrum. Zinc(II) complexes bearing derivatized imidazoles have been explored for possible optoelectronic applications. The structures of two zinc(II) complexes of 5,6‐dimethyl‐2‐(pyridin‐2‐yl)‐1‐[(pyridin‐2‐yl)methyl]‐1H‐benzimidazole (L), namely dichlorido(dimethylformamide‐κO){5,6‐dimethyl‐2‐(pyridin‐2‐yl‐κN)‐1‐[(pyridin‐2‐yl)methyl]‐1H‐benzimidazole‐κN³}zinc(II) dimethylformamide monosolvate, [ZnCl₂(C₂₀H₁₈N₄)(C₃H₇NO)]·C₃H₇NO, (I), and bis(acetato‐κ²O,O′){5,6‐dimethyl‐2‐(pyridin‐2‐yl‐κN)‐1‐[(pyridin‐2‐yl)methyl]‐1H‐benzimidazole‐κN³}zinc(II) ethanol monosolvate, [Zn(C₂H₃O₂)₂(C₂₀H₁₈N₄)]·C₂H₅OH, (II), are reported. Complex (I) crystallized as a dimethylformamide solvate and exhibits a distorted trigonal bipyramidal coordination geometry. The coordination sphere consists of a bidentate L ligand spanning axial to equatorial sites, two chloride ligands in equatorial sites, and an O‐bound dimethylformamide ligand in the remaining axial site. The other complex, (II), crystallized as an ethanol solvate. The Zn^II atom has a distorted trigonal prismatic coordination geometry, with two bidentate acetate ligands occupying two edges and a bidentate L ligand occupying the third edge of the prism. Complexes (I) and (II) emit in the blue region of the spectrum. The results of density functional theory (DFT) calculations suggest that the luminescence of L results from π*←π transitions and that the luminescence of the complexes results from interligand charge‐transfer transitions. The orientation of the 2‐(pyridin‐2‐yl) substituent with respect to the benzimidazole system was found to have an impact on the calculated HOMO–LUMO gap (HOMO is highest occupied molecular orbital and LUMO is lowest unoccupied molecular orbital).     

Synthesis,crystal structures and luminescence properties of seven mononuclear zinc(II), cadmium(II), cobalt(II) and nickel(II) complexes with 5‐(4‐methylphenyl)‐3‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazole

Due to their versatile coordination modes and metal‐binding conformations, triazolyl ligands can provide a wide range of possibilities for the construction of supramolecular structures. Seven mononuclear transition metal complexes with different structural forms, namely aquabis[3‐(4‐methylphenyl)‐5‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazolato‐κ²N ¹,N ⁵]zinc(II), [Zn(C₁₄H₁₁N₄)₂(H₂O)], (I), bis[5‐(4‐methylphenyl)‐3‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazole‐κ²N ³,N ⁴]bis(nitrato‐κO )zinc(II), [Zn(NO₃)₂(C₁₄H₁₂N₄)₂], (II), bis(methanol‐κO )bis[3‐(4‐methylphenyl)‐5‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazolato‐κ²N ¹,N ⁵]zinc(II), [Zn(C₁₄H₁₁N₄)₂(CH₄O)₂], (III), diiodidobis[5‐(4‐methylphenyl)‐3‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazole‐κ²N ³,N ⁴]cadmium(II), [CdI₂(C₁₄H₁₂N₄)₂], (IV), bis[5‐(4‐methylphenyl)‐3‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazole‐κ²N ³,N ⁴]bis(nitrato‐κO )cadmium(II), [Cd(NO₃)₂(C₁₄H₁₂N₄)₂], (V), aquabis[3‐(4‐methylphenyl)‐5‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazolato‐κ²N ¹,N ⁵]cobalt(II), [Co(C₁₄H₁₁N₄)₂(H₂O)], (VI), and diaquabis[3‐(4‐methylphenyl)‐5‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazolato‐κ²N ¹,N ⁵]nickel(II), [Ni(C₁₄H₁₁N₄)₂(H₂O)₂], (VII), have been prepared by the reaction of transition metal salts (Zn^II, Cd^II, Co^II and Ni^II) with 3‐(4‐methylphenyl)‐5‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazole (pymphtzH) under either ambient or hydrothermal conditions. These compounds have been characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray diffraction. All the complexes form three‐dimensional supramolecular structures through hydrogen bonds or through π–π stacking interactions between the centroids of the pyridyl or arene rings. The pymphtzH and pymphtz⁻ entities act as bidentate coordinating ligands in each structure. Moreover, all the pyridyl N atoms are coordinated to metal atoms (Zn, Cd, Co or Ni). The N atom in the 4‐position of the triazole group is coordinated to the Zn and Cd atoms in the crystal structures of (II), (IV) and (V), while the N atom in the 1‐position of the triazolate group is coordinated to the Zn, Co and Ni atoms in (I), (III), (VI) and (VII).     

Three zinc(II) and cadmium(II) complexes containing 4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole and polynitrile ligands: synthesis,molecular and supramolecular structures,and photoluminescence properties

Three photoluminescent complexes containing either Zn^II or Cd^II have been synthesized and their structures determined. Bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(dicyanamido‐κN ¹)zinc(II), [Zn(C₁₂H₁₀N₆)₂(C₂N₃)₂], (I), bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(dicyanamido‐κN ¹)cadmium(II), [Cd(C₁₂H₁₀N₆)₂(C₂N₃)₂], (II), and bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(tricyanomethanido‐κN ¹)cadmium(II), [Cd(C₁₂H₁₀N₆)₂(C₄N₃)₂], (III), all crystallize in the space group P , with the metal centres lying on centres of inversion, but neither analogues (I) and (II) nor Cd^II complexes (II) and (III) are isomorphous. A combination of N—H…N and C—H…N hydrogen bonds and π–π stacking interactions generates three‐dimensional framework structures in (I) and (II), and a sheet structure in (III). The photoluminescence spectra of (I)–(III) indicate that the energies of the π–π* transitions in the coordinated triazole ligand are modified by minor changes of the ligand geometry associated with coordination to the metal centres.     

Iron(III) Catecholates for Cellular Imaging and Photocytotoxicity in Red Light

Iron(III) complexes [Fe( L )( L′ )(NO₃)]—in which L is phenyl‐N,N‐bis[(pyridin‐2‐yl)methyl]methanamine ( 1 ), (anthracen‐9‐yl)‐N,N‐bis[(pyridin‐2‐yl)methyl]methanamine ( 2 ), (pyreny‐1‐yl)‐N,N‐bis[(pyridin‐2‐yl)methyl]methanamine ( 3 – 5 ), and L′ is catecholate ( 1 – 3 ), 4‐tert‐butyl catecholate ( 4 ), and 4‐(2‐aminoethyl)‐benzene‐1,2‐diolate ( 5 )—were synthesized and their photocytotoxic properties examined. The five electron‐paramagnetic complexes displayed a Fe^III/Fe^II redox couple near ?0.4 V versus a saturated calomel electrode (SCE) in DMF/0.1 m tetrabutylammonium perchlorate (TBAP). They showed unprecedented photocytotoxicity in red light (600–720 nm) to give IC₅₀≈15 μM in various cell lines by means of apoptosis to generate reactive oxygen species. They were ingested in the nucleus of HeLa and HaCaT cells in 4 h, thereby interacting favorably with calf thymus (ct)‐DNA and photocleaving pUC19 DNA in red light of 785 nm to form hydroxyl radicals.     

In situ synthesis of mononuclear copper(II) complexes of the new tridentate ligand bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methyl]amine

Two mononuclear copper complexes, {bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl‐κN²)methyl]amine‐κN}(3,5‐dimethyl‐1H‐pyrazole‐κN²)(perchlorato‐κO)copper(II) perchlorate, [Cu(ClO₄)(C₅H₈N₂)(C₁₂H₁₉N₅)]ClO₄, (I), and {bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl‐κN²)methyl]amine‐κN}bis(3,5‐dimethyl‐1H‐pyrazole‐κN²)copper(II) bis(hexafluoridophosphate), [Cu(C₅H₈N₂)₂(C₁₂H₁₉N₅)](PF₆)₂, (II), have been synthesized by the reactions of different copper salts with the tripodal ligand tris[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methyl]amine (TDPA) in acetone–water solutions at room temperature. Single‐crystal X‐ray diffraction analysis revealed that they contain the new tridentate ligand bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methyl]amine (BDPA), which cannot be obtained by normal organic reactions and has thus been captured in the solid state by in situ synthesis. The coordination of the Cu^II ion is distorted square pyramidal in (I) and distorted trigonal bipyramidal in (II). The new in situ generated tridentate BDPA ligand can act as a meridional or facial ligand during the process of coordination. The crystal structures of these two compounds are stabilized by classical hydrogen bonding as well as intricate nonclassical hydrogen‐bond interactions.     

Tuning of crystallization method and ligand conformation to give a mononuclear compound or two‐dimensional SCO coordination polymer based on a new semi‐rigid V‐shaped bis‐pyridyl bis‐amide ligand

With the new semi‐rigid V‐shaped bidentate pyridyl amide compound 5‐methyl‐N,N′‐bis(pyridin‐4‐yl)benzene‐1,3‐dicarboxamide (L) as an auxiliary ligand and the Fe^II ion as the metal centre, one mononuclear complex, bis(methanol‐κO)bis[5‐methyl‐N,N′‐bis(pyridin‐4‐yl)benzene‐1,3‐dicarboxamide‐κN]bis(thiocyanato‐κN)iron(II), [Fe(SCN)₂(C₁₉H₁₆N₄O₂)₂(CH₃OH)₂] ( 1 ), and one two‐dimensional coordination polymer, catena‐poly[[[bis(thiocyanato‐κN)iron(II)]‐bis[μ‐5‐methyl‐N,N′‐bis(pyridin‐4‐yl)benzene‐1,3‐dicarboxamide‐κ²N:N′]] methanol disolvate dihydrate], {[Fe(SCN)₂(C₁₉H₁₆N₄O₂)₂]·2CH₃OH·2H₂O}_n ( 2 ), were prepared by slow evaporation and H‐tube diffusion methods, respectively, indicating the effect of the method of crystallization on the structure type of the target product. Both complexes have been structurally characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray crystallography. The single‐crystal X‐ray diffraction analysis shows that L functions as a monodentate ligand in mononuclear 1 , while it coordinates in a bidentate manner to two independent Fe(SCN)₂ units in complex 2 , with a different conformation from that in 1 and the ligands point in two almost orthogonal directions, therefore leading to a two‐dimensional grid‐like network. Investigation of the magnetic properties reveals the always high‐spin state of the Fe^II centre over the whole temperature range in 1 and a gradual thermally‐induced incomplete spin crossover (SCO) behaviour below 150 K in 2 , demonstrating the influence of the different coordination fields on the spin properties of the metal ions. The current results provide useful information for the rational design of functional complexes with different structure dimensionalities by employing different conformations of the ligand and different crystallization methods.     

Synthesis and characterization of a cadmium(II)–organic supramolecular coordination compound based on the multifunctional 2‐amino‐5‐sulfobenzoic acid ligand

Much attention has been paid by chemists to the construction of supramolecular coordination compounds based on the multifunctional ligand 5‐sulfosalicylic acid (H₃SSA) due to the structural and biological interest of these compounds. However, no coordination compounds have been reported for the multifunctional amino‐substituted sulfobenzoate ligand 2‐amino‐5‐sulfobenzoic acid (H₂asba). We expected that H₂asba could be a suitable building block for the assembly of supramolecular networks due to its interesting structural characteristics. The reaction of cadmium(II) nitrate with H₂asba in the presence of the auxiliary flexible dipyridylamide ligand N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide (4bpme) under ambient conditions formed a new mixed‐ligand coordination compound, namely bis(3‐amino‐4‐carboxybenzenesulfonato‐κO¹)diaquabis{N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide‐κN}cadmium(II)–N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide–water (1/1/4), [Cd(C₇H₆NO₅S)₂(C₁₄H₁₄N₄O₂)₂(H₂O)₂]·C₁₄H₁₄N₄O₂·4H₂O, (1), which was characterized by single‐crystal and powder X‐ray diffraction analysis (PXRD), FT–IR spectroscopy, thermogravimetric analysis (TG), and UV–Vis and photoluminescence spectroscopic analyses in the solid state. The central Cd^II atom in (1) occupies a special position on a centre of inversion and exhibits a slightly distorted octahedral geometry, being coordinated by two N atoms from two monodentate 4bpme ligands, four O atoms from two monodentate 4‐amino‐3‐carboxybenzenesulfonate (Hasba⁻) ligands and two coordinated water molecules. Interestingly, complex (1) further extends into a threefold polycatenated 0D→2D (0D is zero‐dimensional and 2D is two‐dimensional) interpenetrated supramolecular two‐dimensional (4,4) layer through intermolecular hydrogen bonding. The interlayer hydrogen bonding further links adjacent threefold polycatenated two‐dimensional layers into a three‐dimensional network. The optical properties of complex (1) indicate that it may be used as a potential indirect band gap semiconductor material. Complex (1) exhibits an irreversible dehydration–rehydration behaviour. The fluorescence properties have also been investigated in the solid state at room temperature.     

Synthesis and characterization of two novel bimetallic macrocyclic complexes generated from 1,2,4‐triazole‐containing semi‐rigid ligands and M(NO3)2 units (M = Ni and Zn)

Bimetallic macrocyclic complexes have attracted the attention of chemists and various organic ligands have been used as molecular building blocks, but supramolecular complexes based on semi‐rigid organic ligands containing 1,2,4‐triazole have remained rare until recently. It is easier to obtain novel topologies by making use of asymmetric semi‐rigid ligands in the self‐assembly process than by making use of rigid ligands. A new semi‐rigid ligand, 3‐[(pyridin‐4‐ylmethyl)sulfanyl]‐5‐(quinolin‐2‐yl)‐4H‐1,2,4‐triazol‐4‐amine (L), has been synthesized and used to generate two novel bimetallic macrocycle complexes, namely bis{μ‐3‐[(pyridin‐4‐ylmethyl)sulfanyl]‐5‐(quinolin‐2‐yl)‐4H‐1,2,4‐triazol‐4‐amine}bis[(methanol‐κO)(nitrato‐κ²O,O′)nickel(II)] dinitrate, [Ni₂(NO₃)₂(C₁₇H₁₄N₆S)₂(CH₃OH)₂](NO₃)₂, (I), and bis{μ‐3‐[(pyridin‐4‐ylmethyl)sulfanyl]‐5‐(quinolin‐2‐yl)‐4H‐1,2,4‐triazol‐4‐amine}bis[(methanol‐κO)(nitrato‐κ²O,O′)zinc(II)] dinitrate, [Zn₂(NO₃)₂(C₁₇H₁₄N₆S)₂(CH₃OH)₂](NO₃)₂, (II), by solution reactions with the inorganic salts M(NO₃)₂ (M = Ni and Zn, respectively) in mixed solvents. In (I), two Ni^II cations with the same coordination environment are linked by L ligands through Ni—N bonds to form a bimetallic ring. Compound (I) is extended into a two‐dimensional network in the crystallographic ac plane via N—H…O, O—H…N and O—H…O hydrogen bonds, and neighbouring two‐dimensional planes are parallel and form a three‐dimensional structure via π–π stacking. Compound (II) contains two bimetallic rings with the same coordination environment of the Zn^II cations. The Zn^II cations are bridged by L ligands through Zn—N bonds to form the bimetallic rings. One type of bimetallic ring constructs a one‐dimensional nanotube via O—H…O and N—H…O hydrogen bonds along the crystallographic a direction, and the other constructs zero‐dimensional molecular cages via O—H…O and N—H…O hydrogen bonds. They are interlinked into a two‐dimensional network in the ac plane through extensive N—H…O hydrogen bonds, and a three‐dimensional supramolecular architecture is formed via π–π interactions between the centroids of the benzene rings of the quinoline ring systems.     

`0'‐ and `8'‐shaped complexes generated from a nano‐sized oxadiazole‐containing organic ligand with CdI2 and CuI

A new nano‐sized rigid double‐armed oxadiazole‐bridged organic ligand, 2,5‐bis{2‐methyl‐5‐[2‐(pyridin‐3‐yl)ethenyl]phenyl}‐1,3,4‐oxadiazole, C₃₀H₂₀N₄O, L or (I), which adopts a cis conformation in the solid state, has been synthesized and used to create the two novel metallocycle complexes (2,5‐bis{2‐methyl‐5‐[2‐(pyridin‐3‐yl‐κN)ethenyl]phenyl}‐1,3,4‐oxadiazole)diiodidocadmium(II) dichloromethane monosolvate, [CdI₂(C₃₀H₂₀N₄O)]·CH₂Cl₂, (II), and di‐μ‐iodido‐bis[(2,5‐bis{2‐methyl‐5‐[2‐(pyridin‐3‐yl‐κN)ethenyl]phenyl}‐1,3,4‐oxadiazole)copper(I)], [Cu₂I₂(C₃₀H₂₀N₄O)₂], (III). Molecules of complex (II) adopts a 20‐membered `0'‐shaped metallocycle structure with crystallographic mirror symmetry. The discrete units are linked into one‐dimensional chains through intermolecular π–π and C—H...π interactions. In (III), the two I atoms and two Cu<sup>I</sup> atoms form a {Cu<sub>2</sub>(μ‐I)<sub>2</sub>} cluster. One {Cu<sub>2</sub>(μ‐I)<sub>2</sub>} cluster and two L ligands form two 20‐membered monometallic rings in a head‐to‐head fashion, leading to a discrete centrosymmetric `8'‐shaped metallocyclic complex. These metallocycles stack together via two kinds of intermolecular π–π interactions to generate a two‐dimensional network in the ac plane. The luminescence properties of (I)–(III) were investigated in the solid state at room temperature and displayed an obvious red shift.     

One‐dimensional copper(II) coordination polymers based on 1,3‐bis(pyridin‐4‐yl)propane and diimine ligands

Two one‐dimensional (1D) coordination polymers (CPs), namely catena‐poly[[[aqua(2,2′‐bipyridine‐κ²N,N′)(nitrato‐κO)copper(II)]‐μ‐1,3‐bis(pyridin‐4‐yl)propane‐κ²N:N′] nitrate], {[Cu(NO₃)(C₁₀H₈N₂)(C₁₃H₁₄N₂)(H₂O)]·NO₃}_n ( 1 ), and catena‐poly[[[aqua(nitrato‐κO)(1,10‐phenanthroline‐κ²N,N′)copper(II)]‐μ‐1,3‐bis(pyridin‐4‐yl)propane‐κ²N:N′] nitrate], {[Cu(NO₃)(C₁₂H₈N₂)(C₁₃H₁₄N₂)(H₂O)]·NO₃}_n ( 2 ), have been synthesized using [Cu(NO₃)(NN)(H₂O)₂]NO₃, where NN = 2,2′‐bipyridine (bpy) or 1,10‐phenanthroline (phen), as a linker in a 1:1 molar ratio. The CPs were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and single‐crystal X‐ray structure determination. The 1,3‐bis(pyridin‐4‐yl)propane (dpp) ligand acts as a bridging ligand, leading to the formation of a 1D polymer. The octahedral coordination sphere around copper consists of two N atoms from bpy for 1 or phen for 2 , two N atoms from dpp, one O atom from water and one O atom from a coordinated nitrate anion. Each structure contains two crystallographically independent chains in the asymmetric unit and the chains are linked via hydrogen bonds into a three‐dimensional network.     

Two isomorphous ZnII/CoII complexes with tri‐tert‐butoxysilanethiol and histamine,and (4‐hydroxymethyl‐1H‐imidazole‐κN)bis(tri‐tert‐butoxysilanethiolato‐κ2O,S)zinc(II)

The complexes [2‐(1H‐imidazol‐4‐yl‐κN³)ethylamine‐κN]bis(tri‐tert‐butoxysilanethiolato‐κS)cobalt(II), [Co(C₁₂H₂₇O₃SSi)₂(C₅H₉N₃)], and [2‐(1H‐imidazol‐4‐yl‐κN³)ethylamine‐κN]bis(tri‐tert‐butoxysilanethiolato‐κS)zinc(II), [Zn(C₁₂H₂₇O₃SSi)₂(C₅H₉N₃)], are isomorphous. The central Zn^II/Co^II ions are surrounded by two S atoms from the tri‐tert‐butoxysilanethiolate ligand and by two N atoms from the chelating histamine ligand in a distorted tetrahedral geometry, with two intramolecular N—H...O hydrogen‐bonding interactions between the histamine NH₂ groups and tert‐butoxy O atoms. Molecules of the complexes are joined into dimers via two intermolecular bifurcated N—H...(S,O) hydrogen bonds. The Zn^II atom in [(1H‐imidazol‐4‐yl‐κN³)methanol]bis(tri‐tert‐butoxysilanethiolato‐κ²O,S)zinc(II), [Zn(C₁₂H₂₇O₃SSi)₂(C₄H₆N₂O)], is five‐coordinated by two O and two S atoms from the O,S‐chelating silanethiolate ligand and by one N atom from (1H‐imidazol‐4‐yl)methanol; the hydroxy group forms an intramolecular hydrogen bond with sulfur. Molecules of this complex pack as zigzag chains linked by N—H...O hydrogen bonds. These structures provide reference details for cysteine‐ and histidine‐ligated metal centers in proteins.     

Coordination of a triazine ligand with CuII and AgI investigated by spectral,structural, theoretical and docking studies

Two complexes of 5‐phenyl‐3‐(pyridin‐2‐yl)‐1,2,4‐triazine (PPTA), namely (ethanol‐κO)bis(nitrato‐κO)[5‐phenyl‐3‐(pyridin‐2‐yl‐κN)‐1,2,4‐triazine‐κN²]copper(II), [Cu(NO₃)₂(C₁₄H₁₀N₄)(C₂H₆O)] or [Cu(NO₃)₂(PPTA)(EtOH)] ( 1 ), and bis[μ‐5‐phenyl‐3‐(pyridin‐2‐yl)‐1,2,4‐triazine]‐κ³N¹:N²,N³;κ³N²,N³:N¹‐bis[(nitrato‐κO)silver(I)], [Ag₂(NO₃)₂(C₁₄H₁₀N₄)₂] or [Ag₂(NO₃)₂(μ‐PPTA)₂] ( 2 ), were prepared and characterized by elemental analysis, FT–IR spectroscopy and single‐crystal X‐ray diffraction. The X‐ray structure analysis of 1 revealed a copper complex with square‐pyramdial geometry containing two O‐donor nitrate ligands along with an N,N′‐donor PPTA ligand and one O‐donor ethanol ligand. In the binuclear structure of 2 , formed by the bridging of two PPTA ligands, each Ag atom has an AgN₃O environment and square‐planar geometry. In addition to the four dative interactions, each Ag atom interacts with two O atoms of two nitrate ligands on adjacent complexes to complete a pseudo‐octahedral geometry. Density functional theory (DFT) calculations revealed that the geometry around the Cu and Ag atoms in 1 ^opt and 2 ^opt (opt is optimized) for an isolated molecule is the same as the experimental results. In 1 , O—H…O hydrogen bonds form R₁²(4) motifs. In the crystal network of the complexes, in addition to the hydrogen bonds, there are π–π stacking interactions between the aromatic rings (phenyl, pyridine and triazine) of the ligands on adjacent complexes. The ability of the ligand and complexes 1 and 2 to interact with ten selected biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS, Top II and B‐DNA) was investigated by docking studies. The results show that the studied compounds can interact with proteins better than doxorubicin (except for TrxR and Top II).     

Killing two birds with one stone: 2D+2D→3D parallel stacking and 3D self‐penetrating structures in one reaction and their crystal‐to‐crystal transformation

Reaction of the flexible phenolic carboxylate ligand 2‐(3,5‐dicarboxylbenzyloxy)benzoic acid (H₃L) with nickel salts in the presence of 1,2‐bis(pyridin‐4‐yl)ethylene (bpe) leads to the generation of a mixture of the two complexes under solvolthermal conditions, namely poly[[aqua[μ‐1,2‐bis(pyridin‐4‐yl)ethylene‐κ²N:N′]{μ‐5‐[(2‐carboxyphenoxy)methyl]benzene‐1,3‐dicarboxylato‐κ³O¹,O^1′:O³}nickel(II)] dimethylformamide hemisolvate monohydrate], {[Ni(C₁₆H₁₀O₇)(C₁₂H₁₀N₂)(H₂O)]·0.5C₃H₇NO·H₂O}_n or {[Ni(HL)(bpe)(H₂O)]·0.5DMF·H₂O}_n, 1 , and poly[[diaquatris[μ‐1,2‐bis(pyridin‐4‐yl)ethylene‐κ²N:N′]bis{μ‐5‐[(2‐carboxyphenoxy)methyl]benzene‐1,3‐dicarboxylato‐κ²O¹:O⁵}nickel(II)] dimethylformamide disolvate hexahydrate], {[Ni₂(C₁₆H₁₀O₇)₂(C₁₂H₁₀N₂)₃(H₂O)₂]·2C₃H₇NO·6H₂O}_n or {[Ni₂(HL)₂(bpe)₃(H₂O)₂]·2DMF·6H₂O}_n, 2 . In complex 1 , the Ni^II centres are connected by the carboxylate and bpe ligands to form two‐dimensional (2D) 4‐connected (4,4) layers, which are extended into a 2D+2D→3D (3D is three‐dimensional) supramolecular framework. In complex 2 , bpe ligands connect to Ni^II centres to form 2D layers with Ni₆(bpe)₆ metallmacrocycles. Interestingly, 2D+2D→3D inclined polycatenation was observed between these layers. The final 5‐connected 3D self‐penetrating structure was generated through further connection of Ni–carboxylate chains with these inclined motifs. Both complexes were fully characterized by single‐crystal analysis, powder X‐ray diffraction analysis, FT–IR spectra, elemental analyses, thermal analysis and UV–Vis spectra. Notably, an interesting metal/ligand‐induced crystal‐to‐crystal transformation was observed between the two complexes.     

Dinuclear cobalt and nickel complexes of a mercaptoacetic acid substituted 1,2,4‐triazole ligand: syntheses,structures and urease inhibitory studies

Because of its versatile coordination modes and strong coordination ability, the mercaptoacetic acid substituted 1,2,4‐triazole 2‐{[5‐(pyridin‐2‐yl)‐4H‐1,2,4‐triazol‐3‐yl]sulfanyl}acetic acid ( H₂L ) was synthesized and characterized. Treatment of H₂L with cobalt and nickel acetate afforded the dinuclear complexes {μ‐3‐[(carboxylatomethyl)sulfanyl]‐5‐(pyridin‐2‐yl)‐4H‐1,2,4‐triazol‐4‐ido‐κ²N¹,N⁵:N²,O}bis[aqua(methanol‐κO)cobalt(II)] methanol disolvate, [Co₂(C₉H₆N₄O₂S)₂(CH₃OH)₂(H₂O)₂]·2CH₃OH ( 1 ), and {μ‐3‐[(carboxylatomethyl)sulfanyl]‐5‐(pyridin‐2‐yl)‐4H‐1,2,4‐triazol‐4‐ido‐κ²N¹,N⁵:N²,O}bis[diaquanickel(II)] methanol disolvate dihydrate, [Ni₂(C₉H₆N₄O₂S)₂(H₂O)₄]·2CH₃OH·2H₂O ( 2 ), respectively. Complex 1 crystallized in the monoclinic space group P2₁/c, while 2 crystallized in the tetragonal space group I4₁/a. Single‐crystal X‐ray diffraction studies revealed that H₂L is doubly deprotonated and acts as a tetradentate bridging ligand in complexes 1 and 2 . For both of the obtained complexes, extensive hydrogen‐bond interactions contribute to the formation of their three‐dimensional supermolecular structures. Hirshfeld surface analysis was used to illustrate the intermolecular interactions. Additionally, the urease inhibitory activities of 1 , 2 and H₂L were investigated against jack bean urease, where the two complexes revealed strong urease inhibition activities.     

Hydrogen bonding and π–π interactions in the cocrystal salt [Fe(bpe)2(H2O)4](TCEP)2·2(bpe) [bpe is trans‐1,2‐bis(pyridin‐4‐yl)ethene and TCEP is 1,1,3,3‐tetracyano‐2‐ethoxypropenide]

The cocrystal salt tetraaquabis[trans‐1,2‐bis(pyridin‐4‐yl)ethene‐κN]iron(II) bis(1,1,3,3‐tetracyano‐2‐ethoxypropenide)–trans‐1,2‐bis(pyridin‐4‐yl)ethene (1/2), [Fe(C₁₂H₁₀N₂)₂(H₂O)₄](C₉H₅N₄O)₂·2C₁₂H₁₀N₂, is a rare example of a mononuclear Fe^II compound with trans‐1,2‐bis(pyridin‐4‐yl)ethane (bpe) ligands. The complex cation resides on a crystallographically imposed inversion center and exhibits a tetragonally distorted octahedral coordination geometry. Both the symmetry‐independent bpe ligand and the cocrystallized bpe molecule are essentially planar. The 1,1,3,3‐tetracyano‐2‐ethoxypropenide counter‐ion is nonplanar and the bond lengths are consistant with significant electron delocalization. The extended structure exhibits an extensive O—H…N hydrogen‐bonding network with layers of complex cations joined by the cocrystallized bpe. Both the coordinated and the cocrystallized bpe are involved in π–π interactions. Hirshfeld and fingerprint plots reveal the important intermolecular interactions. Density functional theory was used to estimate the strengths of the hydrogen‐bonding and π–π interactions, and suggest that the O—H…N hydrogen bonds enhance the strength of the π‐interactions by increasing the polarization of the pyridine rings.     

Syntheses and structures of three macrocyclic supramolecular complexes and one ZnII‐containing coordination polymer generated from a semi‐rigid multidentate N‐containing ligand

Semirigid organic ligands can adopt different conformations to construct coordination polymers with more diverse structures when compared to those constructed from rigid ligands. A new asymmetric semirigid organic ligand, 4‐{2‐[(pyridin‐3‐yl)methyl]‐2H‐tetrazol‐5‐yl}pyridine ( L ), has been prepared and used to synthesize three bimetallic macrocyclic complexes and one coordination polymer, namely, bis(μ‐4‐{2‐[(pyridin‐3‐yl)methyl]‐2H‐tetrazol‐5‐yl}pyridine)bis[dichloridozinc(II)] dichloromethane disolvate, [Zn₂Cl₄(C₁₂H₁₀N₆)₂]·2CH₂Cl₂, ( I ), the analogous chloroform monosolvate, [Zn₂Cl₄(C₁₂H₁₀N₆)₂]·CHCl₃, ( II ), bis(μ‐4‐{2‐[(pyridin‐3‐yl)methyl]‐2H‐tetrazol‐5‐yl}pyridine)bis[diiodidozinc(II)] dichloromethane disolvate, [Zn₂I₄(C₁₂H₁₀N₆)₂]·2CH₂Cl₂, ( III ), and catena‐poly[[[diiodidozinc(II)]‐μ‐4‐{2‐[(pyridin‐3‐yl)methyl]‐2H‐tetrazol‐5‐yl}pyridine] chloroform monosolvate], {[ZnI₂(C₁₂H₁₀N₆)]·CHCl₃}_n, ( IV ), by solution reaction with ZnX₂ (X = Cl and I) in a CH₂Cl₂/CH₃OH or CHCl₃/CH₃OH mixed solvent system at room temperature. Complex ( I ) is isomorphic with complex ( III ) and has a bimetallic ring possessing similar coordination environments for both of the Zn^II cations. Although complex ( II ) also contains a bimetallic ring, the two Zn^II cations have different coordination environments. Under the influence of the I^? anion and guest CHCl₃ molecule, complex ( IV ) displays a significantly different structure with respect to complexes ( I )–( III ). C—H…Cl and C—H…N hydrogen bonds, and π–π stacking or C—Cl…π interactions exist in complexes ( I )–( IV ), and these weak interactions play an important role in the three‐dimensional structures of ( I )–( IV ) in the solid state. In addition, the fluorescence properties of L and complexes ( I )–( IV ) were investigated.