Tailoring Enhanced Elasticity of Crystalline Coordination Polymers.

The approach for enhancing the elasticity of crystals with suboptimal elastic performances through a rational design was presented. A hydrogen-bonding link was identified as a critical feature in the structure of the parent material, the Cd(II) coordination polymer [CdI2(I-pz)2] n (I-pz = iodopyrazine), to determine the mechanical output and was modified via cocrystallization. Small organic coformers resembling the initial organic ligand but with readily available hydrogens were selected to improve the identified link, and the extent of strengthening the critical link was in an excellent correlation with the delivered enhancement of elastic flexibility materials.

Exploring the Co-Crystallization Landscape of One-Dimensional Coordination Polymers Using a Molecular Electrostatic Potential-Driven Approach.

The ability of coordination polymers (CPs) to form multicomponent heteromeric materials, where the key structural features of the parent CP are retained, has been explored via molecular electrostatic potential-driven co-crystallization technologies. Thirteen co-formers presenting hydrogen-bond donors activated through a variety of electron-withdrawing functionalities were employed, and the extent of activation was evaluated using molecular electrostatic potential values. Attempted co-crystallizations of the seven most promising co-formers with a family of nine CPs ([CdX'2(X-pz)2]n; X' = I, Br, and Cl; X = I, Br, and Cl) resulted in six successful outcomes; all four of the structurally characterized compounds displayed the intended hydrogen bond. The rationalization of the main structural features revealed that strict structural and electrostatic requirements were imposed on effective co-formers; only co-formers with highly activated hydrogen-bond donors, and with a 1,4-orientation of electron-withdrawing moieties bearing effective acceptor sites, were successfully implemented into the three-dimensional architectures composed of one-dimensional building units of CPs.

Anion-assisted supramolecular assemblies of zinc(II) complexes with isonicotinamide.

Five zinc(II) coordination compounds, [ZnCl2(isn)2] (1), [ZnBr2(isn)2] (2), [Zn(NO3)2(H2O)(isn)2] (3), [Zn(CH3COO)2(isn)]2 (4) and [Zn(isn)4(H2O)2](ClO4)2 (5) (isn = isonicotinamide), were prepared by the reactions of the isonicotinamide (pyridine-4-carboxamide, isn) and corresponding zinc(II) salts. Their crystal structures were determined by the single-crystal X-ray diffraction method. The coordination environment of zinc(II) is tetrahedral in the compounds containing small halide anions (chloride, bromide), 1 and 2. An expansion of the zinc(II) coordination environment to the octahedral is observed in the presence of the monodentate and bridging nitrate ions in 3. The coordination environments of both zinc(II) ions in dimeric acetate complex 4 is also enlarged in the comparison with 1 and 2, one zinc(II) ion being octahedrally coordinated and the other being pentacoordinated. The zinc(II) ion in 5 also reaches higher coordination environment (octahedral), which is enabled by binding of additional water molecules, since the perchlorate ion is uncoordinated. The supramolecular amide-amide homosynthon R 2 2 ( 8 ) is preserved in the presence of halide, nitrate and acetate ions (1-4), but it is completely disrupted in the crystal packing of 5 due to the presence of the bulky perchlorate anion. Spectroscopic analysis of compounds 1-5 was performed by IR spectroscopy in the solid state and by 13C NMR spectroscopy in the DMSO solutions. The NMR data support a complete decomposition of 3 in the DMSO solution, but 1, 2, 4 and 5 remain unchanged in the solution. Thermal properties of the coordination compounds were also investigated by TGA and DSC methods.

Correction to Two-Dimensional Anisotropic Flexibility of Mechanically Responsive Crystalline Cadmium(II) Coordination Polymers.

[This corrects the article DOI: 10.1021/acs.chemmater.2c00062.].

Two-Dimensional Anisotropic Flexibility of Mechanically Responsive Crystalline Cadmium(II) Coordination Polymers.

Crystals of a family of six one-dimensional (1D) coordination polymers of cadmium(II) with cyanopyridines [[CdX2L2] n , where X = Cl, Br, or I and L = 3-cyanopyridine (3-CNpy) or 4-cyanopyridine (4-CNpy)] presented a variety of morphologies and mechanical responses with dominant two-dimensional (2D) anisotropic flexibility, which has not been previously reported. All mechanically adaptable crystals were 2D flexible and displayed a variety of direction-dependent responses; in addition to 2D isotropic flexibility observed for solely elastic materials, 2D anisotropic flexibility was noticed for both elastic and elastic → plastic crystals. The consequences of fine and controlled structural variations on mechanical behavior were additionally explored via microfocus single-crystal X-ray diffraction and complementary theoretical studies, revealing that the relative strength and direction of the hydrogen bonding interactions were the key parameters in delivering a specific mechanical response.

Synthesis and crystal structure of a 6-chloro-nicotinate salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4'-bi-pyridine.

A 6-chloro-nicotinate (6-Clnic) salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4'-bi-pyridine (4,4'-bpy), namely, catena-poly[[[tetra-aqua-nickel(II)]-µ-4,4'-bi-pyridine-κ2 N:N'] bis-(6-chloro-nicotinate) tetra-hydrate], {[Ni(C10H8N2)(H2O)4](C6H3ClNO2)2·4H2O} n or {[Ni(4,4'-bpy)(H2O)4](6-Clnic)2·4H2O} n , (1), was prepared by the reaction of nickel(II) sulfate hepta-hydrate, 6-chloro-nicotinic acid and 4,4'-bi-pyridine in a mixture of water and ethanol. The mol-ecular structure of 1 comprises a one-dimensional polymeric {[Ni(4,4'-bpy)(H2O)4]2+} n cation, two 6-chloro-nicotinate anions and four water mol-ecules of crystallization per repeating polymeric unit. The nickel(II) ion in the polymeric cation is octa-hedrally coordinated by four water mol-ecule O atoms and by two 4,4'-bi-pyridine N atoms in the trans position. The 4,4'-bi-pyridine ligands act as bridges and, thus, connect the symmetry-related nickel(II) ions into an infinite one-dimensional polymeric chain extending along the b-axis direction. In the extended structure of 1, the polymeric chains of {[Ni(4,4'-bpy)(H2O)4]2+} n , the 6-chloro-nicotinate anions and the water mol-ecules of crystallization are assembled into an infinite three-dimensional hydrogen-bonded network via strong O-H⋯O and O-H⋯N hydrogen bonds, leading to the formation of the representative hydrogen-bonded ring motifs: tetra-meric R 2 4(8) and R 4 4(10) loops, a dimeric R 2 2(8) loop and a penta-meric R 4 5(16) loop.

The first coordination compound of 6-fluoro-nicotinate: the crystal structure of a one-dimensional nickel(II) coordination polymer containing the mixed ligands 6-fluoro-nicotinate and 4,4'-bi-pyridine.

A one-dimensional nickel(II) coordination polymer with the mixed ligands 6-fluoro-nicotinate (6-Fnic) and 4,4'-bi-pyridine (4,4'-bpy), namely, catena-poly[[di-aqua-bis-(6-fluoro-pyridine-3-carboxyl-ato-κO)nickel(II)]-µ-4,4'-bi-pyri-dine-κ2 N:N'] trihydrate], {[Ni(6-Fnic)2(4,4'-bpy)(H2O)2]·3H2O} n , (1), was prepared by the reaction of nickel(II) sulfate hepta-hydrate, 6-fluoro-nicotinic acid (C6H4FNO2) and 4,4'-bi-pyridine (C10H8N2) in a mixture of water and ethanol. The nickel(II) ion in 1 is octa-hedrally coordinated by the O atoms of two water mol-ecules, two O atoms from O-monodentate 6-fluoro-nicotinate ligands and two N atoms from bridging 4,4'-bi-pyridine ligands, forming a trans isomer. The bridging 4,4'-bi-pyridine ligands connect symmetry-related nickel(II) ions into infinite one-dimensional polymeric chains running in the [10] direction. In the extended structure of 1, the polymeric chains and lattice water mol-ecules are connected into a three-dimensional hydrogen-bonded network via strong O-H⋯O and O-H⋯N hydrogen bonds, leading to the formation of distinct hydrogen-bond ring motifs: octa-meric R 8 8(24) and hexa-meric R 8 6(16) loops.

The first coordination compound of deprotonated 2-bromo-nicotinic acid: crystal structure of a dinuclear paddle-wheel copper(II) complex.

A copper(II) dimer with the deprotonated anion of 2-bromo-nicotinic acid (2-BrnicH), namely, tetrakis(µ-2-bromonicotinato-κ2 O:O')bis[aquacopper(-II)](Cu-Cu), [Cu2(H2O)2(C6H3BrNO2)4] or [Cu2(H2O)2(2-Brnic)4], (1), was prepared by the reaction of copper(II) chloride dihydrate and 2-bromo-nicotinic acid in water. The copper(II) ion in 1 has a distorted square-pyramidal coordination environment, achieved by four carboxyl-ate O atoms in the basal plane and the water mol-ecule in the apical position. The pair of symmetry-related copper(II) ions are connected into a centrosymmetric paddle-wheel dinuclear cluster [Cu⋯Cu = 2.6470 (11) Å] via four O,O'-bridging 2-bromo-nicotinate ligands in the syn-syn coordination mode. In the extended structure of 1, the cluster mol-ecules are assembled into an infinite two-dimensional hydrogen-bonded network lying parallel to the (001) plane via strong O-H⋯O and O-H⋯N hydrogen bonds, leading to the formation of various hydrogen-bond ring motifs: dimeric R 2 2(8) and R 2 2(16) loops and a tetra-meric R 4 4(16) loop. The Hirshfeld surface analysis was also performed in order to better illustrate the nature and abundance of the inter-molecular contacts in the structure of 1.

Exploring and predicting intermolecular binding preferences in crystalline Cu(ii) coordination complexes.

A simple model focusing on electrostatic contributions to interaction energies was found to be very effective for rationalizing the appearance of specific supramolecular interactions in a series of Cu(ii) coordination compounds. The experimental space was provided by a combination of Cu(ii) cations with acac-based anions (hexafluoracetylacetonato and trifluoracetylacetonato) and a series of pyridine-oxime ligands (3-pyridinealdoxime, methyl 3-pyridyl ketoxime, 4-pyridinealdoxime, methyl 4-pyridyl ketoxime, phenyl 4-pyridyl ketoxime). The calculated molecular electrostatic potential (MEP) values at competing hydrogen-bond acceptor sites, for ten structurally characterized complexes, provided guidelines for predicting supramolecular connectivity in cases when the MEP difference exceeded certain cut-off values, while two different and well-defined outcomes are possible within the so called 'grey zone', delineated by a range of MEP differences. It was also shown that the structural outcome within this region is determined by the influence of relatively weak, but distinct, auxillary interactions.

Mechanically Responsive Crystalline Coordination Polymers with Controllable Elasticity.

Crystalline coordination polymers tend to be brittle and inelastic, however, we now describe a family of such compounds that are capable of displaying mechanical elasticity in response to external pressure. The design approach successfully targets structural features that are critical for producing the desired mechanical output. The elastic crystals all comprise 1D cadmium(II) halide polymeric chains with adjacent metal centres bridged by two halide ions resulting in the required stacking interactions and short "4 Å" crystallographic axes. These polymeric chains (structural "spines") are further organized via hydrogen bonds and halogen bonds perpendicular to the direction of the chains. By carefully altering the strength and the geometry of these non-covalent interactions, we have demonstrated that it is possible to control the extent of elastic bending in crystalline coordination compounds.

Building inorganic supramolecular architectures using principles adopted from the organic solid state.

In order to develop transferable and practical avenues for the assembly of coordination complexes into architectures with specific dimensionality, a strategy utilizing ligands capable of simultaneous metal coordination and self-complementary hydrogen bonding is presented. The three ligands used, 2(1H)-pyrazinone, 4(3H)-pyrimidinone and 4(3H)-quinazolinone, consistently deliver the required synthetic vectors in a series of CdII coordination polymers, allowing for reproducible supramolecular synthesis that is insensitive to the different steric and geometric demands from potentially disruptive counterions. In all nine crystallographically characterized compounds presented here, directional intermolecular N-H⋯O hydrogen bonds between ligands on adjacent complex building blocks drive the assembly and orientation of discrete building blocks into largely predictable topologies. Furthermore, whether the solids are prepared from solution or through liquid-assisted grinding, the structural outcome is the same, thus emphasizing the robustness of the synthetic protocol. The details of the molecular recognition events that take place in this series of compounds have been clearly delineated and rationalized in the context of calculated molecular electrostatic potential surfaces.

A new tecton with parallel halogen-bond donors: a path to supramolecular rectangles.

A new tecton, 1,8-diiodoethynylanthracene, with two halogen-bond donor sites was synthesized and characterized. This tecton is capable of forming two parallel halogen bonds at once, which makes it a useful building block for the construction of a variety of supramolecular squares and rectangles.

Impact of Coordinated Pseudohalide Ions and Picolinamide on Supramolecular Synthons in Selected Zinc and Cadmium Complexes.

Four new Zn(II) and Cd(II) picolinamide (pia) complexes with cyanate and azide, e.g. [Zn(OCN)2(pia)2] (1), [Cd(OCN)2(pia)2]n (2), [Zn(N3)2(pia)2] (3) and [Cd(N3)2(pia)2]n·nH2O (4), have been prepared and characterized by IR and NMR spectroscopy, and thermal (TG/DTA) methods. For the compounds 1 and 3 X-ray analysis revealed mononuclear molecular structure with octahedral N4O2 environment around the zinc(II) center with cis-arrangement of ligands. Only in 1 the amide head-to-head supramolecular motifs, represented by an R2(2) (8) designator, are observed, while in 3 none of the typical amide motifs were found. While the IR data suggests the polymeric structures for 2 and 4 in the solid state, all the NMR spectra agree with the monomeric structure of the compounds in the solution.

Interactions with polynucleotides and antitumor activity of amidino and imidazolinyl substituted 2-phenylbenzothiazole mesylates.

Based on previously reported antiproliferative activity screening, four most promising disubstituted 2-phenylbenzothiazole hydrochlorides were chosen for detailed study. Water solubility, as well as liphophilicity/hydrophilicity balance of organic core were modified by conversion to mesylate salts. For purpose of structure/activity studies their structures were determined by X-ray structure analysis. Detailed analysis of interactions of new compounds with double stranded (ds-) DNA/RNA by UV/Vis and CD titrations, thermal melting and viscometry experiments revealed that most of studied compounds intercalate into ds-RNA but bind into minor groove of AT-DNA, and agglomerate along GC-DNA. Furthermore, compounds also interact with ss-RNA, but only amino-imidazolinyl 2-phenylbenzothiazole, 4b displayed well defined orientation and dominant binding mode (by induced CD signals) with poly A and poly G. Besides, in vitro investigations revealed moderate to high antiproliferative activity of benzothiazoles against seven human cancer cell lines, while in some cases (HTC 116, SW620, MIA PaCa-2) high correlation between the type of the amidino group and cytotoxic activity was observed.

N-(4-Methyl-benz-yl)-3-nitro-anilinium chloride.

The cation of the title compound, C(14)H(15)N(2)O(2) (+)·Cl(-), comprises two almost ideally planar systems, 3-nitro-phenyl (r.m.s. deviation = 0.0117 Å) and 4-methyl-phenyl (r.m.s. deviation = 0.238 Å), separated by the central C-N bond, and with their mean planes inclined to one another by 61.36 (5)°. In the crystal, hydrogen-bonded chains running along [001] are generated by connecting neighbouring mol-ecules via N-H⋯Cl hydrogen bonds and consolidated by C-H⋯Cl and C-H⋯O inter-actions. Within these chains, fused R(2) (1)(6) and R(3) (2)(10) ring motifs are formed. Parallel chains are further linked into a two-dimensional network parallel to (100) via C-H⋯O inter-actions.

N-(4-Methyl-benz-yl)-3-nitro-aniline.

In the title compound, C(14)H(14)N(2)O(2), the angle between the mean plane of the N-methyl-3-nitro-aniline system (r.m.s. deviation = 0.0185 Å) and the p-tolyl unit is 89.79 (4)°. In the crystal, hydrogen-bonded chains running along [10-1] are generated by the linking of neighbouring mol-ecules via N-H⋯O and C-H⋯O hydrogen bonds involving the 3-nitro-aniline systems and forming R(2) (2)(8) motifs.

6-Iodo-2-methyl-1,3-benzothia-zole.

The title compound, C(8)H(6)INS, is essentially planar, the largest deviation from the mean plane being for the I atom [0.075 (3) Å]. The crystal structure is mainly stabilized by inter-molecular C-I⋯N halogen bonds, forming zigzag supra-molecular chains in [10]. Relatively short off-set π-π contacts [centroid-centroid distance = 3.758 (2) Å] between the thia-zole rings of inversion-related mol-ecules link neighbouring chains and provide the secondary inter-actions for building the crystal structure.

Uncommon isonicotinamide supramolecular synthons in copper(II) complexes directed by nitrate and perchlorate anions.

The title compounds, trans-diaquabis(nitrato-kappaO)bis(pyridine-4-carboxamide-kappaN(1))copper(II), [Cu(NO(3))(2)(C(6)H(6)N(2)O)(2)(H(2)O)(2)], (I), and trans-diaquatetrakis(pyridine-4-carboxamide-kappaN(1))copper(II) bis(perchlorate), [Cu(C(6)H(6)N(2)O)(4)(H(2)O)(2)](ClO(4))(2), (II), are composed of mononuclear coordination entities involving Cu(II) ions and isonicotinamide. In (I), the centrosymmetric tetragonally distorted octahedral copper(II) environment contains trans-related isonicotinamide and water molecules in the equatorial plane and two nitrate ions occupying the axial sites. In (II), the equatorial plane of the C(2)-symmetric distorted octahedron is built up of four isonicotinamide ligands, while water molecules occupy the axial positions. The complex molecules of (I) and (II) are linked into three-dimensional supramolecular frameworks by O-H...O and N-H...O hydrogen bonds. The nitrate and perchlorate ions are building blocks that disturb the robust R(2)(2)(8) amide supramolecular motif commonly found in crystal structures of copper-isonicotinamide complexes.

cis-Bis(azido-κN)bis-(pyridine-2-carbox-amide-κN,O)nickel(II).

The title compound, [Ni(N(3))(2)(C(6)H(6)N(2)O)(2)], was obtained as the first crystalline product from the reaction of Ni(NO(3))(2)·6H(2)O, picolinamide and NaN(3) in aqueous media. After a few days in the mother liquor, crystals of the cis isomer transformed into the trans isomer [Dakovic & Popovic (2007 ▶). Acta Cryst. C63, m507-m509]. The Ni atom exhibits a distorted octa-hedral environment and contains two azide ions and two planar N,O-chelating picolinamide ligands, all cis related. The dihedral angle between the two chelate rings is 82.43 (7)°. Pairs of mol-ecules are linked by N-H⋯N hydrogen bonds into cyclic R(2) (2)(16) dimers, which are further packed into a three-dimensional framework by C(6) and C(8) chains by N-H⋯N hydrogen bonds.

(Nitrato-kappaO)bis(pyridine-2-carboxamide-kappa2N1,O)mercury(II) nitrate.

In the title compound, [Hg(NO3)(C6H6N2O)2]NO3, the Hg(II) atom is five-coordinate. The distorted square-pyramidal mercury(II) coordination environment is achieved by two N,O-bidentate picolinamide ligands, with one O-monodentate nitrate ion in the apical position. A seven-coordinate extended coordination environment is completed by two additional weak Hg...O interactions, one from the coordinated nitrate ion and one from the other nitrate ion, to give seven-coordination. The molecules are linked into a two-dimensional network by N-H...O hydrogen bonds.