Donor Linkers Research Articles

Synthesis of Symmetrically and Unsymmetrically Substituted Cationic Diborane(4) Compounds with Distinct Structural Motifs and Properties

AbstractThe introduction of electron‐donating, bridging guanidinate substituents in diborane(4) compounds allows the synthesis of a variety of new cationic diborane(4) compounds. In this work, strategies for the directed synthesis of cationic di‐ and tetraboron compounds are presented, leading to the synthesis and complete characterization of several new compounds with distinct structural motifs, all exhibiting BIIatoms directly bound to each other. Hence, we report on tetracationic donor‐acceptor cyclophanes with diboron donor linkers and organic π‐acceptor units, on paddlewheel‐type cationic diboranes, and on unsymmetrically‐substituted monocationic diboranes.

Rational design and construction of a serious of highly water-stable coordination polymers with various N, N′-donor linkers: Syntheses, diversity structures, and dye adsorption property

In this study, we have synthesized six new coordination polymers (CPs), namely {[Cu6(3,5-bip)6(H2O)12(SO4)6]·3H2O}n (1), [Co(3,5-bip) (H2O)3(SO4)]n (2), {[Cu(1,3-bit)2(H2O)2]·2(NO3)}n (3), {[Cu2(1,3-bit)2 (1,3-bcbb)2]·4(H2O)}n (4), [Cu(4,4′-bibp) (H2O) (NO3)2]n (5), [Cu(4,4′-bibp) (4,4′-Hsbdc)]n (6) via solvothermal methods. The structures of these new CPs have been characterized by elemental analysis, FTIR, TG analysis, PXRD and single crystal X-ray diffraction techniques. Meanwhile, the title CPs are explored for adsorption of organic dyes, i.e., anionic dyes (congo red (CR), and methyl orange (MO)) and cationic dye (methylene blue (MB)) considered extensively as water colorants pollutants. Worth noting, complex 3 can adsorb anionic dyes (CR and MO) quickly; complex 6 shows great performance in CR adsorption. Kinetic study reveals that the adsorption process is performed via pseudo-second-order reaction. The dye removal investigations of complexes 3 and 6 support that ions exchange and H-bonding interactions between CPs and target organic dyes are significant factors, heavily affecting dye adsorption. They have excellent potential in wastewater treatment.

Seven Zn(II) and Cd(II) 1D coordination polymers based on azine donor linkers and decorated with 2-thiophenecarboxylate: Syntheses, structural parallels, Hirshfeld surface analysis, and spectroscopic and inclusion properties

Seven mixed-ligand 1D coordination polymers [Zn2(4-bphz)(2-tpc)4]n (1), [Zn2(4-bpmhz)(2-tpc)4]n (2), [Cd(4-bphz)2(2-tpc)2]n (3), [Zn(3-bphz)(2-tpc)2]n (4), [Zn(3-bpmhz)(2-tpc)2]n (5), [Cd(4-bpmhz)(2-tpc)2]n·0.5n(4-bpmhz) (6), [Cd(3-bpmhz)(2-tpc)2]n·0.5n(H2O) (7) (where 2-tpc = 2-thiophenecarboxylate, 4-bphz = 1,2-bis(pyridin-4-ylmethylene) hydrazine, 4-bpmhz = 1,2-bis(1-(pyridin-4-yl)ethylidene)hydrazine, 3-bphz = 1,2-bis(pyridin-3-ylmethylene)hydrazine, and 3-bpmhz = 1,2-bis(1-(pyridin-3-yl)ethylidene)hydrazine) were prepared and studied using spectroscopic (FTIR, UV–Vis) and X-ray diffraction methods of analysis. Similarly, four bidentate-bridging azine ligands provide the polymers’ extension, while the different mononuclear/binuclear metal nodes demonstrate the variable metals’ coordination capacities that influence the crystal packing motifs and inclusion properties. The guest-free arrays 1–5 pack in parallel stacking modes, while the inclusion compounds 6 and 7 reveal criss-cross packing arrangements with large channels where guest molecules (4-bpmhz/water) serve as structure-directing templates in the formation of crystal structures. The distributions of different types of intermolecular interactions with respect to the percentage of stacking interactions in 1–7 were quantified by Hirshfeld surface and fingerprint plots analysis. The guest-exchange properties for 6 and the solid state emissive properties for 1–7 are reported.

Chromism, positional, conformational and structural isomerism in a series of Zn(II) and Cd(II) coordination polymers based on methylated azine N,N′-donor linkers

Seven new coordination polymers [Zn(I)2(4-bpmhz)]n (1), [Cd(I)2(4-bpmhz)]n (2), [Zn(I)2(3-bpmhz)]n (3), [Cd(I)2(3-bpmhz)2]n (4), [Zn(NO3)2(H2O)2(4-bpmhz)]n·0.5n(EtOH) (5), [Cd(NO3)2(4-bpmhz)3/2(MeOH)]n·0.5nH2O (6) and [Zn(NO3)2(3-bpmhz)2]n (7) were prepared following the reactions of the zinc and cadmium iodide or nitrate salts with the methylated azine ligands of the bis-monodentate N,N′-donor type, 1,2-bis(1-(pyridin-4-yl)ethylidene)hydrazine (4-bpmhz) and 1,2-bis(1-(pyridin-3-yl)ethylidene)hydrazine (3-bpmhz). The single-crystal X-ray diffraction studies show that compounds 1–5, and 7 display 1D chain structures, while compound 6 shows a 2D coordination network, and both 4-bpmhz and 3-bpmhz act as bidentate bridging ligands. The crystals 1 and 2 are isomorphous, and differ by the metal cation only. The single coordination chains in 1–3 have zigzag structures; they are linear in 5, while 4 and 7 display similar double-chain structures. The crystal packing in 5 and 6 provides cavities occupied by solvent molecules, ethanol and water. The compounds were characterized in the solid state and in solution by spectroscopic (FTIR, UV–Vis, NMR) methods; the solid state emissive properties were studied for all compounds, while their thermal stability and behaviour were investigated by thermogravimetry under inert atmosphere, while the thermochromism for several compounds was registered and discussed.

Metallo-macrocycles from a library of flexible linkers: 1D cobalt(II) coordination polymers and a supramolecular pipe

Three cobalt(II) coordination polymers containing compounds {Co(3-mboba)(1,2-bix)2}n (1), {Co2(1,3-pda)(px3ampy)(H2O)2}n (2), {Co2(hfipbb)2(bpbix)2}n (3), that are formed from three different bent carboxylic acids [3,3′-methylenebis(oxy)dibenzoic acid (3-H2mboba), 2,2′-(1,3-phenylene)diacetic acid (1,3-H2pda) and 4,4′-(perfluoropropane-2,2-diyl)dibenzoic acid (H2hfipbb)] as primary ligands and three different {N,N}-donor linkers [1,2-bis((1H-imidazol-1-yl)methyl)benzene(1,2-bix), N,N′-(1,4-phenylenebis(methylene)) dipyridin-3-amine (px3ampy) and 4,4′-bis((1H-imidazol-1-yl)methyl)biphenyl (bpbix)] as secondary ligands, have been synthesized under hydrothermal conditions. Compounds 1–3 are characterized by single crystal X-ray diffraction analysis, IR spectroscopy, thermogravimetric (TG) and elemental analysis. Single crystal X-ray crystallography shows that diverse metallo-macrocycles are formed in compounds 1, 2 and 3. In the crystal structure of compound 1, two different metallo-macrocyles, 28-membered metal–acid {Co2(3-mboba)2} ring and 24-membered metal-N-linker {Co2(1,2-bix)2} ring, are formed. The alternative arrangement of these macrocylic rings leads to the formation of 1D chainlike coordination polymer (compound 1). In the crystal of compound 2, a 25-membered macrocycle ring {Co(1,3-pda)(px3ampy)} is formed from one dicarboxylic acid ligand and one {N,N}ligand, which further undergoes coordination with itself resulting in the formation of 1D chain. The {Co3(hfipbb)(bpbix)2} metallamacrocycle, observed in the crystal structure of compound 3, is more diversified in the sense that it is relatively bigger in size and this trinuclear metallo-macrocycle is formed by one dicaryboxylic acid ligand and two {N,N} donor linkers, but not in a plane. Interestingly, the inter-linking of these non-planar macrocycles results in the construction of a supramolecular pipe.

Rare Supramolecular Assemblies of a Dicopper(II)‐tetracarboxylate Stabilized by (Methanol)6, Dimethyl Sulfoxide and 4,4′‐Azobipyridyl Bridges

AbstractTwo new supramolecular assemblies formed by [Cu2(Hdiphba)4] (H2diphba=4‐hydroxy‐3,5‐di‐iso‐propylbenzoic acid) in protic and aprotic solvents have been investigated. Methanol gives rise a 3D hydrogen‐bonded network comprised of [Cu2(Hdiphba)4] and extremely rare twisted‐boat methanol cyclohexamer synthons. While, dimethyl sulfoxide (DMSO), an aprotic solvent, gives a 2D assembly in which DMSO bridges [Cu2(Hdiphba)4] units to form 1D rectangular channels, entrapping guest DMSO arranged in a zig‐zag chain. The solvent molecules could be replaced with neutral N,N’‐donor linkers to form 1D coordination polymers.

Organic-inorganic hybrid materials from divalent metal cations and expanded N,N′-donor linkers

Abstract The rod-shaped linker (E,E)-N,N′-(3,3′-dimethyl-4,4′-biphenyldiyl)bis[1-(3-pyridinyl)methanimine] (L) is exploited for the first time in the synthesis of extended structures. Four new coordination polymers of composition {[ZnL(OAc)2]·EtOH}n (1), {[CdL(OAc)2]·MeOH}n (2), {[Cu2L(OAc)4]·CH2Cl2}n (3) and [MnL(N3)2]n (4) have been structurally characterized. The metal cations and the anionic ancillary ligands play pivotal roles for the topology of these compounds. In the crystalline reaction products of Zn(II), Cd(II) and Cu(II) acetate with the organic linker, the acetate anions connects two neighboring cations to dinuclear [M2(OAc)4] subunits. These secondary building units are further crosslinked by the N,N′-donor ligand, either perpendicular to the acetato bridges, leading to a ladder-like ribbon for 1 and 2, or in the direction of the metal···metal separation, resulting in a simple chain in the case of 3. Instead of dinuclear secondary building units, a different topology results from reaction of the N,N′ linker with Mn(ClO4)2 in the presence of azide anions: 1,3 bridging by the N3 − groups leads to infinite chains. These are crosslinked by L in perpendicular direction, and the layer structure 4 is obtained. Natural bond orbital (NBO) analyses revealed information on the basis of orbital interactions about the coordination environments of the metal ions. Thermogravimetric measurements indicate the highest thermal stability for 2. Strong antiferromagnetic coupling within the dinuclear subunits of 3 is observed as a consequence of superexchange via the acetato bridges.

Cd(II) coordination polymers based on expanded N,N′-heteroaromatic donor ligands

The isomeric N donor linkers bis(pyridin-4-ylmethylene)naphthalene-1,5-diamine (L1) and bis(pyridin-3-ylmethylene)naphthalene-1,5-diamine (L2) have been used with acetate and iodide as co-ligands to generate four new cadmium(II) coordination polymers. [CdL1(OAc)2]n (1), [CdL1(I)2]n (2), [CdL2(OAc)2]n (3) and [CdL2(I)2]n (4) were characterized by elemental analysis, X-ray powder diffraction, IR spectroscopy, thermal analysis and single crystal X-ray diffraction. In line with the concept of crystal engineering, their structures share common motifs: the heteroaromatic linkers generate chains, subtending Cd⋯Cd distances consistent with their N donor arrangement. The co-ligands control the coordination number of the Cd(II) cations and interchain connectivity: The acetate moieties either adopt bridging and chelating or exclusively bridging modes and crosslink essentially linear chains based on octahedral metal centers; in the former case, the ladder-like one-dimensional ribbon 1 is generated, whereas the latter connectivity results in the two-dimensional layer structure 3. In contrast, iodide acts as terminal ligand towards tetrahedral Cd(II), and hence 2 and 4 are single-stranded 1D zig-zag polymers. In comparison to the uncoordinated heteroaromatic L1 and L2, the Cd coordination polymers show slightly red-shifted luminescence spectra of significantly higher intensity due to the more rigid arrangement of the π systems.

Construction of diverse dimensionality in eight coordination polymers of bivalent metal ions using 5-nitroisophthalate and different linear N,N′-donor linkers

Assembly of 5-nitroisophthalate (nip2−) with first row transition metal salts [Mn(II), Fe(II), Co(II), Zn(II)] in combination with the various neutral auxiliary N,N′-donor linkers, e.g., 2,5-bis-(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), 1,3-bis(4-pyridyl)propane (bpp) and 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb), yielded eight new coordination polymers (CPs), namely {[Mn(4-bpdh)(nip)(H2O)2]·H2O}n (1), {[Fe(4-bpdh)(nip)(H2O)2]·H2O}n (2), {[Co(4-bpdh)(nip)(H2O)2]·H2O}n (3), {[Mn2(bpp)2(nip)2(H2O)2]·H2O}n (4), {[Fe(bpp)(nip)(H2O)]·H2O}n (5), [Zn(bpp)(nip)(H2O)]n (6), {[Fe(4-bpdh)1.5(nip)]·(4-bpdh)0.5}n (7) and {[Fe(4-bpdb)(nip)]·(4-bpdb)0.5(H2O)}n (8) using the slow diffusion technique at room temperature. The complexes 1–8 were characterized by single crystal X-ray diffraction analysis and were further characterized by elemental analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD). Complexes 1–3 are isostructural and exhibit a one-dimensional (1D) metal-carboxylate chain with pendant 4-bpdh ligands, which is further extended into a three-dimensional supramolecular structure by means of H-bonding and π–π interactions. Complexes 4–6 are also isomorphous, but distinctly different from the first three complexes. They exhibit a similar 2-fold interpenetrated three-dimensional (3D) net with 66 dia net topology. Compound 7 displays a two-dimensional (2D) grid-like structure, having 4-bpdh ligands in the crystal void, and this is further extended by means of intermolecular π–π interactions into a 3D supramolecular structure, whereas compound 8 possesses a different 2D grid structure containing free 4-bpdb ligands in the void spaces. The thermal stabilities and UV–Vis spectra of all the complexes and the luminescent properties of complex 6 were also studied.

Flexible dicarboxylate based pillar-layer metal organic frameworks: differences in structure and porosity by tuning the pyridyl based N,N′ linkers

Dicarboxylate supported metal organic hybrids of Co(II), Zn(II) and Cd(II) have been synthesized using two different pyridyl based N,N′ linkers having Schiff base functionalized site. The use of flexible dicarboxylate glutarate in designing such frameworks has created a marked diversity in topology. The different N,N′ donor linkers also played an active part in the channel modification in the synthesized MOFs. The structural and topological diversity has been analyzed from the single crystal X-ray structure. Five compounds, {[Co(azpy)(glut)]·(CH3OH)}n (1), {[Co(meazpy)(glut)(H2O)2]·(H2O)3}n (2), {[Zn(azpy)0.5(glut)(H2O)]·(azpy)0.5}n (3), {[Zn(meazpy)0.5(glut)(H2O)]·(H2O)2}n (4) and {[Cd(azpy)(glut)]·(CH3OH)}n (5), show porous structures with solvent accessible voids. The nature of the pores as well as the existence of lattice solvent molecules in 1 and 2 are different due to the use of a different pillar ligand in their fabrication. In case of 3 and 4 there are some nice effects of non-covalent interaction in the construction of their solid state structure, which has also originated by the change of pillar N,N′ donor linkers. Complex 5 is topologically as well as structurally similar to 1 forming a 2D-grid like structure. In {[Cd2(meazpy)2(glut)(NO3)]2}n (6) there is a formation of 2D sheets with the coordinated counter anion. Interestingly, here the sheets are disposed in a perpendicular fashion to each other and do not contain any solvent accessible void. Upon removal of the solvent molecules, the frameworks 1–5 show moderate CO2 and H2 uptake at 273 K and 77 K, respectively. The desolvated frameworks show different quantities of CO2 and H2 uptake which has been corroborated to their structures.

Design and Synthesis of 60° Dendritic Donor Ligands and Their Coordination-Driven Self-Assembly into Supramolecular Rhomboidal Metallodendrimers

The design and self-assembly of novel rhomboidal metallodendrimers via coordination-driven self-assembly is described. By employing newly designed 60° ditopic donor linkers substituted with Fréchet-type dendrons and appropriate 120° rigid di-Pt(II) acceptor subunits, a variety of [G-1]-[G-3] rhomboidal metallodendrimers with well-defined shape and size were prepared under mild conditions in high yields. The supramolecular metallodendrimers were characterized with multinuclear NMR ((1)H and (31)P), mass spectrometry (CSI-TOF-MS), and elemental analysis. Isotopically resolved mass spectrometry data support the existence of the metallodendrimers with rhomboidal cavities, and NMR data were consistent with the formation of all ensembles. The shape and size of all rhomboidal metallodendrimers were investigated with the PM6 semiempirical molecular orbital method.

ChemInform Abstract: Metal‐Organic Frameworks: A Rapidly Growing Class of Versatile Nanoporous Materials

AbstractReview: 168 refs.

Metal‐Organic Frameworks: Metal‐Organic Frameworks: A Rapidly Growing Class of Versatile Nanoporous Materials (Adv. Mater. 2/2011)

AbstractMetal‐organic frameworks (MOFs) represent a new class of hybrid organic‐inorganic supramolecular materials comprised of ordered networks formed from organic electron donor linkers and metal cations. They can exhibit extremely high surface areas, as well as tunable pore size and functionality, and can act as hosts for a variety of guest molecules. Since their discovery, MOFs have enjoyed extensive exploration, with applications ranging from gas storage to drug delivery to sensing. This review covers advances in the MOF field from the past three years, focusing on applications, including gas separation, catalysis, drug delivery, optical and electronic applications, and sensing. We also summarize recent work on methods for MOF synthesis and computational modeling.

Metal‐Organic Frameworks: A Rapidly Growing Class of Versatile Nanoporous Materials

Metal-organic frameworks (MOFs) represent a new class of hybrid organic-inorganic supramolecular materials comprised of ordered networks formed from organic electron donor linkers and metal cations. They can exhibit extremely high surface areas, as well as tunable pore size and functionality, and can act as hosts for a variety of guest molecules. Since their discovery, MOFs have enjoyed extensive exploration, with applications ranging from gas storage to drug delivery to sensing. This review covers advances in the MOF field from the past three years, focusing on applications, including gas separation, catalysis, drug delivery, optical and electronic applications, and sensing. We also summarize recent work on methods for MOF synthesis and computational modeling.

Facile self-assembly of neutral dendritic metallocycles via oxygen-to-platinum coordination.

A new approach for the fabrication of neutral dendritic metallocycles is described. By combining rigid 120 degrees dicarboxylate donor linkers funtionalized with [G0]-[G3] Frechet-type dendrons and complementary rigid 60 degrees and 120 degrees di-Pt(II) acceptor subunits, neutral rhomboidal metallodendrimers and hexagonal metallodendrimers, respectively, were prepared under mild conditions in high yields. The assemblies have well-defined shapes and sizes and were characterized by multinuclear NMR ((1)H and (31)P), mass spectrometry (ESI (+)-TOF-MS and APPI(+)-TOF-MS), and elemental analysis. Isotopically resolved mass spectrometry data support the formation of the neutral [2 + 2] rhomboidal, and [3 + 3] hexagonal metallodendrimers, and NMR data are consistent with the formation of all ensembles. The structures of the [G0] and [G1] neutral rhomboidal metallodendrimers (3a and 3b) were unambiguously confirmed via single-crystal X-ray crystallography. The shape and size of [G3] neutral hexagonal metallodendrimer 5d was established with MMFF force-field simulations.

Coordination-Driven Self-Assembly of Metallodendrimers Possessing Well-Defined and Controllable Cavities as Cores

The design and self-assembly of novel cavity-cored metallodendrimers via noncovalent interactions are described. By employing [G0]-[G3] 120 degrees ditopic donor linkers substituted with Fréchet-type dendrons and appropriate rigid di-Pt(II) acceptor subunits, [G0]-[G3]-rhomboidal metallodendrimers and [G0]-[G3]-hexagonal, "snowflake-shaped" metallodendrimers with well-defined shape and size were prepared under mild conditions in high yields. The assemblies were characterized with multinuclear NMR ((1)H and (31)P), mass spectrometry (ESI-MS and ESI-FT-ICR-MS), and elemental analysis. Isotopically resolved mass spectrometry data support the existence of the metallodendrimers with rhomboidal and hexagonal cavities, and NMR data are consistent with the formation of all ensembles. The structures of [G0]- and [G1]-rhomboidal metallodendrimers were unambiguously confirmed via single-crystal X-ray crystallography. The shape and size of two [G3]-hexagonal metallodendrimers were investigated with MM2 force-field modeling.

Self-assembly of gold(i) with diphosphine and bitopic nitrogen donor linkers in the presence of trifluoroacetate anion: formation of coordination polymer versus discrete macrocycle

The rigid Au2(dppbz)(CF3COO)2 (1) precursor (dppbz = 1,2-bis(diphenylphosphino)benzene) with preorganised syn-gold(I) centers has been self-assembled with 4,4′-bipyridyl (bipy) and 1,2-trans-bis(4-pyridyl)-ethylene (bipyen) to afford different supramolecular architectures: a unique [Au2(dppbz)(bipy)]n(CF3COO)2n (2) coordination polymer and a discrete [Au4(dppbz)2(bipyen)2](CF3COO)4 (3) macrocycle in response to changes in bitopic nitrogen donor linker.

Self-Assembly of Three-Dimensional M3L2 Cages via a New Flexible Organometallic Clip

The simple combination of tritopic pyridine donor linkers with a new flexible acceptor "clip" in a 2:3 stoichiometric ratio generates three-dimensional M3L2 cages which possess large cavities in essentially quantitative yields.

Synthesis and Structural Characterization of Carborane-Containing Neutral, Self-Assembled Pt-Metallacycles

[structure: see text] We have combined carborane chemistry with the newly developed directional bonding strategy to synthesize neutral macrocycles. The m- and p-carborane dicarboxylates were utilized as the donor linkers in conjunction with 1,8-bis[trans-Pt(PEt3)2NO3]anthracene 3, 2,9-bis[trans-Pt(PEt3)2NO3]phenanthrene 5, and cis-Pt(PEt3)2(NO3)2 unit 6. Three new platinum-based macrocycles, 4, 7, and 8, were thus synthesized. 31P{1H} NMR as well as the X-ray characterization of Pt-metallacycles reveal the formation of single highly symmetrical neutral species.

Facile self-assembly of predesigned neutral 2D pt-macrocycles via a new class of rigid oxygen donor linkers.

Self-assembly of rigid oxygen donor dicarboxylates such as terephthalate and fumarate with a platinum-containing clip-like acceptor unit afforded neutral macrocyclic rectangles which have been characterized by X-ray single-crystal structure analysis as well as NMR spectroscopy.