Tetrahedral Coordination Mode Research Articles

Heteronuclear metal–organic framework‐based fluorescent sensor for the detection of tetracycline antibiotics

The residues of tetracycline antibiotics (TCs) have caused serious environmental pollution due to the multi‐field application. In order to rapidly detect TCs, there is an urgent need to design new fluorescence sensor. Herein, a heterometallic metal‐organic framework (HNU‐61) is constructed and used as a fluorescence sensor for detecting the TCs. InHNU‐61, both Zn2+and Li+ions are assembled into the crystal structure, in which Zn2+adopts tetrahedral coordination mode, and can be served as the potential coordination site. The 3D structure ofHNU‐61is formed by the connection between Zn2+/Li+and isophthalic acid (m‐BDC2−) ligand with the 1D channel alongaaxis. Among the six categories of antibiotics,HNU‐61can effectively detect TCs, including tetracycline hydrochloride (TCY), chlortetracycline hydrochloride (CTE), doxycycline hydrochloride (DOX), and oxytetracycline hydrochloride (OXY) with the detection limits of 6.5 × 10−8 M, 9.2 × 10−8 M, 4.5 × 10−7 M, and 3.9 × 10−7 M, respectively. Furthermore,HNU‐61enables a rapid and sensitive detection of TCs with good anti‐interference and circulation. The detection mechanism can be attributed to the interaction between Zn2+inHNU‐61and TCs.

Luminescent agostic Cu(I) complexes containing both trigonal planar and tetrahedral coordination modes

Reaction of [Cu(MeCN)4]ClO4 with 1H-imidazo[4,5-f][1,10]phenanthroline derivatives (L1, L2 and L3) and the bulky, rigid chelating diphosphine ligand 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene (xantphos) under alkaline conditions in different ratios afforded a series of luminescent binuclear [Cu2(L–H)(xantphos)2]ClO4 (L=L1, 1a; L2, 2a; L3, 3a) and trinuclear [Cu3(L–2H)(xantphos)3]ClO4 (L=L1, 1b; L2, 2b; L3, 3b) complexes. Both trigonal planar and tetrahedral coordination modes of Cu(I) centers were observed for complexes 1a and 1b, and they exhibit obvious CH⋯Cu agostic or anagostic interaction for the trigonal planar Cu(I) centers. The 31P NMR, electronic absorption and emission spectra are discussed. All the complexes exhibit weak luminescence at room temperature in the solid state and in the solution.

“On−Off” Au(I)···Cu(I) Interactions in a Au(NHC)2 Luminescent Vapochromic Sensor

Reaction of the Au(I) N-heterocyclic carbene (NHC) compound [Au(im(CH(2)py)(2))(2)]PF(6) with 2 equiv of [Cu(MeCN)(4)]PF(6) affords the tricationic compound [Au(im(CH(2)py)(2))(2)(Cu(MeCN)(2))(2)](PF(6))(3) (1), which exhibits blue luminescence (lambda(max) = 462 nm). Reaction of 1 with either liquid MeOH or MeOH vapor affords [Au(im(CH(2)py)(2))(2)(Cu(MeOH))(2)](PF(6))(3) (2), which produces green luminescence (lambda(max) = 520 nm) under UV excitation. The molecular structures of 1 x 2MeCN and 2 x 2MeOH.2Et(2)O were determined by single-crystal X-ray diffraction. Compound 1 contains a linearly coordinated [Au(NHC)(2)](+) core in which each picolyl side arm bridges a [Cu(MeCN)(2)](+) center. The Au...Cu separations are long at 4.596 A. Compound 2 exhibits two short Au...Cu interactions of 2.7195(7) A, with the Au(NHC)(2) core acting as an additional ligand toward each copper center to complete its tetrahedral coordination mode. Exposure of 2 to atmosphere produces a partial loss of MeOH accompanied by a luminescence color change to yellow (lambda(max) = 543 nm). The uptake and loss of MeOH vapor is rapid and reversible. Exposure of 2 to vacuum affords complete loss of MeOH, and the luminescence changes to yellow-orange (lambda(max) = 573 nm). Treatment of 2 with MeCN vapor regenerates 1. The interconversion of 1 and 2 was confirmed by powder X-ray diffraction. Compound 1 also reacts with acetone and H(2)O vapors, leading to species that produce yellow-orange (lambda(max) = 591 nm) and green (lambda(max) = 519 nm) emission, respectively. Compounds 1 and 2 are examples of molecular vapochromic materials that exhibit large changes in the emission though ligand substitution reactions between the solid complex and solvent vapors. The dramatic color change likely results from the "on-off" Au...Cu interactions induced by the ligand exchange reaction.

Oligonuclear Homoleptic Copper(I) Pyrazolates with Multinucleating Ligand Scaffolds: High Structural Diversity in Solid-State and Solution

The synthesis of three pyrazole-based, potentially binucleating ligands 3,5-bis(R(1)N(CH(3))CH(2))-4-R(2)pyrazole (L(1)H: R(1) = pyridyl-2-methyl-, R(2) = Ph; L(2)H: R(1) = 8-quinolyl-, R(2) = H; L(3)H: R(1) = 8-quinolyl-, R(2) = Ph) is described. Reaction of L(1-3)H with 1 equiv. of mesitylcopper affords oligonuclear homoleptic complexes of the type [CuL](n) (1-3). The single crystal X-ray structure of 2 shows a tetranuclear assembly of linear coordinated copper(I)-centers bridged by pyrazolato ligands that alternate above and below the Cu(4) plane, with additional weak interactions from some of the ligand side arms. As the single crystal X-ray structure of 3 reveals, phenyl substitution at the 4-position of the pyrazolato framework leads to significant structural modification of the Cu(4) array, giving a rhombical tetranuclear complex with two linear coordinated copper(I) centers that exhibit a short intramolecular Cu...Cu contact (2.8212(10) A) and two peripheral copper(I) centers in a distorted tetrahedral coordination mode. Thus, 3 represents a very rare example of an inorganic pyrazolato cuprate which can also be viewed as a partly rearranged structural isomer of 2. Furthermore, the crystal lattice of 3 shows an extended network of intra- and intermolecular pi-pi stacking interactions between the aromatic rings. In solution, 1-3 each form two types of oligomers a and b that slowly (<1 s(-1)) equilibrate at room temperature. Using Diffusion Ordered Spectroscopy (DOSY) and variable temperature (1)H NMR spectroscopy it can be shown that a and b correspond to a tetrameric and a (planar) trimeric species. Coordination of the pyridyl/quinolyl side arms that is observed in the solid state seems to be only transient in solution.

A chiral twofold interpenetrated diamond-like 3D In(III) coordination network with 4,4′,4″-phosphoryltribenzoate

Abstract A novel In(III) coordination complex, [In(ptc)(H2O)]n (H3ptc = 4,4′,4″-phosphoryltribenzoic acid) (1), was synthesized under hydrothermal condition and characterized by single-crystal X-ray analysis, IR, X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and solid-state photoluminescence. Complex 1 crystallizes in a chiral P21 space group, In(III) ions are eight-coordinated and the ligand exhibits a novel and unique tetrahedral coordination mode. The complex shows intense blue emission at 435 nm with the excitation of 330 nm.

The Aerosol‐Assisted CVD of Silver Films from Single‐Source Precursors

AbstractThin films of silver are deposited from tetraphenyldioxoimidodiphosphinato silver(I) [Ag{(OPPh2)2N}]4 · 2H2O (1) and silver(I) triflouoroacetate CF3COOAg (2) single‐source precursors (SSPs) by the aerosol‐assisted (AA)CVD method. The complex (1) is a tetramer with linear and distorted tetrahedral coordination modes at silver. Two types of films, silvery and brownish, are observed from both SSPs due to the temperature gradient in the AACVD reactor. The as‐deposited films are characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray (EDX) analysis, and ultraviolet/visible (UV‐vis) spectroscopy methods.

μ-Hydroxido-bis[(2,2′-bipyridine)tricarbonylrhenium(I)] perrhenate

The title compound, [Re2(OH)(C10H8N2)2(CO)6][ReO4], is a mixed-valence rhenium compound containing discrete anions and cations. The ReI atoms are in a slightly distorted octa­hedral environment, whereas the ReVII atoms show the typical tetra­hedral coordination mode. The dihedral angle between the two bipyridine groups is 34.3 (7)°.

Novel dithioether–silver(i) coordination architectures: structural diversities by varying the spacers and terminal groups of ligands

An investigation into the dependence of the framework formation of coordination architectures on ligand spacers and terminal groups was reported based on the self-assembly of AgClO4 and eight structurally related flexible dithioether ligands, RS(CH2)nSR (Lan, R = ethyl group; Lbn, R = benzyl group, n= 1-4). Eight novel metal-organic architectures, [Ag(La1)3/2ClO4]n (1a), [Ag2(La2)2(ClO4)2]2 (2a), [AgLa3ClO4]n (3a), {[Ag(La4)2]ClO4}n (4a), [AgLb1ClO4]2 (1b), [Ag(Lb2)2]ClO4 (2b), {[Ag(Lb3)3/2(ClO4)1/2](ClO4)1/2}n (3b) and [Ag(Lb4)3/2ClO4]n(4b), were synthesized and structurally characterized by X-ray crystallography. Structure diversities were observed for these complexes: 1a forms a 2-D (6,3) net, while 2a is a discrete tetranuclear complex, in which the AgI ion adopts linear and tetrahedral coordination modes, and the S donors in each ligand show monodentate terminal and mu2-S bridging coordination fashions; 3a has a chiral helical chain structure in which two homo-chiral right-handed single helical chains (Ag-La3-)n are bound together through mu2-S donors, and simultaneously gives rise to left-handed helical entity (Ag-S-)n. In 4a, left- and right-handed helical chains formed by the ligands bridging AgI centers are further linked alternately by single-bridging ligands to form a non-chiral 2-D framework. 1b has a dinuclear structure showing obvious ligand-sustained Ag-Ag interaction, while 2b is a mononuclear complex; 3b is a 3-D framework formed by ClO4- linking the 2-D (6,3) framework, which is similar to that of 1a, and 4b has a single, double-bridging chain structure in which 14-membered dinuclear ring units formed through two ligands bridging two AgI ions are further linked by single-bridging ligands. In addition, a systematic structural comparison of these complexes and other reported AgClO4 complexes of analogous dithioether ligands indicates that the ligand spacers and terminal groups take essential roles on the framework formation of the AgI complexes, and this present feasible ways for adjusting the structures of such complexes by modifying the ligand spacers and terminal groups.

Nature of metal binding sites in Cu(II) complexes with histidine and related N-coordinating ligands, as studied by EXAFS.

Knowledge of the complexes formed by N-coordinating ligands and Cu(II) ions is of relevance in understanding the interactions of this ion with biomolecules. Within this framework, we investigated Cu(II) complexation with mono- and polydentate ligands, such as ammonia, ethylenediamine (en), and phthalocyanine (Pc). The obtained Cu-N coordination distances were 2.02 A for [Cu(NH(3))(4)](2+), 2.01 A for [Cu(en)(2)](2+), and 1.95 A for CuPc. The shorter bond distance found for CuPc is attributed to the macrocyclic effect. In addition to the structure of the first shell, information on higher coordination shells of the chelate ligands could be extracted by EXAFS, thus allowing discrimination among the different coordination modes. This was possible due to the geometry of the complexes, where the absorbing Cu atoms are coplanar with the four N atoms forming the first coordination shell of the complex. For this reason multiple scattering contributions become relevant, thus allowing determination of higher shells. This knowledge has been used to gain information about the structure of the 1:2 complexes formed by Cu(II) ions with the amino acids histidine and glycine, both showing a high affinity for Cu(II) ions. The in-solution structure of these complexes, particularly that with histidine, is not clear yet, probably due to the various possible coordination modes. In this case the square-planar arrangements glycine-histamine and histamine-histamine as well as tetrahedral coordination modes have been considered. The obtained first-shell Cu-N coordination distance for this complex is 1.99 A. The results of the higher shells EXAFS analysis point to the fact that the predominant coordination mode is the so-called histamine-histamine one in which both histidine molecules coordinate Cu(II) cations through N atoms from the amino group and from the imidazole ring.

Complexation of Cobalt(II) at the Upper Rim of Two New Calix[4]arene/Bipyridine-Based Podands

Introduction of one or two 2,2′-bipyridine units at the upper rim of the calix[4]arene platform was performed by means of the Wittig reaction. The resulting alkenes were hydrogenated to give two new bipyridyl-based calixarene podands, which were studied as ligands for CoII cation. The mono-bipyridyldichlorocobalt complex was notably fully characterised by 1H-NMR and X-ray crystal structure analyses, which confirmed the tetrahedral coordination mode involving the bipyridyl subunit and the two chlorine atoms around the cobalt centre.

Supramolecular motifs in metal complexes of Schiff bases. Part 5. Zinc(II)-assisted self-assembly of some bis-N,N- and N,O-bidentate Schiff bases and chiral packing modes in solid state

Zinc(II)-assisted self-assembly of a new bis-N,O-bidentate Schiff base ligand, (N-salicylidene-4,4′-diaminodiphenyl)methane (L16) with two chelating sites linked by a spacer group (-C6H4CH2C6H4-), afforded in high yield the double-helical dinuclear complex (L16 : ZnII = 2∶2). Single-crystal X-ray analyses demonstrated clearly that the two ZnII centers have a distorted tetrahedral (Td) coordination sphere with two-wrapped ligands. The analogous Schiff base, bis[4-(2-pyridylmethyleneaminophenyl]methane (L17) was also designed to self-assemble in the presence of metal ions, leading to a triple-helical dinuclear (L17∶ZnII = 3∶2) supramolecular motif. Each zinc ion has six-coordinate octahedral geometry with six nitrogens from three ligands. These unprecedented helical motifs in the solid state and solution seem to be induced by the geometrical preference for octahedral or tetrahedral coordination mode of the ZnII ion and the interligand π-stacking interactions between the spacer groups of L16 and L17. Electrospray mass spectrometry proved a very useful characterisational tool in detecting the distribution of supramolecular species in solution. Use of a N,N′-bis(2-pyridylmethylene)-1,4-diaminobenzene (L35) with a rigid phenylene spacer in its center resulted in the one-dimensional zigzag polymeric structure ((L35∶ZnII)∞ = (1∶1)∞) where the multiple π-stacking interactions operate between the aromatic rings of linking ligands. Each zinc ion is octahedrally coordinated by two N,N-bidentate arms of two different ligands and two cis oxygens from N,N-dimethylformamide as coordinating solvent.

Fractionation of Boron Isotopes to Bis(2-hydroxyalkyl)amine Borate and Boric Acid in Aqueous Solutions

Abstract 10B is more fractionated to B(OH)L {H2L: a ligand having a bis(2-hydroxyalkyl)amino group (alkyl: ethyl and propyl)} with a tetrahedral coordination mode than to B(OH)3 with a planar triangular coordination mode in aqueous solutions, exhibiting an isotope separation factor of 1.027 at 25 °C, which is greater than the upper limit of anion exchangers.

Synthesis, structure and spectroscopic properties of [Cu3(μ-dpnapy)3(CH3CN)][ClO4]3·CH3CN (dpnapy = 7-diphenylphosphino-2,4-dimethyl-1,8-naphthyridine) with a linear copper atom array

The co-ordination chemistry of 7-diphenylphosphino-2,4-dimethyl-1,8-naphthyridine (dpnapy) with CuI has been examined. Reaction of [Cu(CH3CN)4][ClO4] with dpnapy in CH3CN afforded [Cu3(µ-dpnapy)3(CH3CN)][ClO4]3 1[ClO4]3. The crystal structure of 1[ClO4]3·CH3CN reveals a linear Cu–Cu–Cu array with both trigonal and tetrahedral co-ordination modes for the copper atoms. The intramolecular Cu–Cu distances of 2.449(2) and 2.721(2) A suggest that only two of the copper atoms have a bonding interaction. Complex 1 reacts with triphenylphosphine (PPh3) and 2,2′-bipyridine (bpy) to give [Cu(bpy)(dpnapy)2][ClO4] 2[ClO4] and [Cu2(µ-dpnapy)3][ClO4]2 3[ClO4]2, respectively. Spectroscopic properties of the complexes have been examined.

Synthesis and some properties of T-cage type Co III4Hg II4 and Rh III4Hg II4 octanuclear complexes with 2-aminoethanethiolate

The reaction of fac( S)-[M(aet) 3] (M = Co III, Rh IIII; aet = 2-aminoehanethiolate) with HgO in water produced T-cage type octanuclear complexes, [{ M(aet) 3} 4 Hg III 4 O] 6+ ( M = CO III ( 1); Rh III ( 2)) , although a similar reaction with HgCl 2 has given only the S-bridged pentanuclear complex. 1 and 2 gave only two isomers, ΔΔΔΔ and ΛΛΛΛ, and they were optically resolved. The obtained isomers were characterized on the basis of electronic absorption, circular dichroism (CD), 1H and 13C NMR spectral and electrochemical behavior. The Hg(II) atoms in the complex cation take tetrahedral coordination modes and the T-cage type octanuclear structure is formed selectively in the present reaction conditions. The selective formations of the polynuclear complexes with the Hg(II) atoms were discussed in comparison with the corresponding polynuclear complexes with the Zn(II) and Cd(II) atoms.