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The processing of metal–organic frameworks as films is the first step toward localizing them for device fabrication. Herein, we investigated the fabrication of polycrystalline, phase pure and highly oriented [Cu2(bdc)2(bpy)]n thin films on bare and chemically modified mesoporous titania surfaces, using a modified layer-by-layer method. While a film consisting of randomly oriented crystals was formed on a bare TiO2 surface, we were able to show that [Cu2(bdc)2(bpy)]n nanoplates in the thin film could adopt perpendicular alignment upon the addition of acetic acid as a modulating agent. It was found that the addition of acetic acid promotes the growth of crystals mostly along [010] direction, provided that it is added to the metal solution. The effects of the modulator addition sequence and amount, reaction temperature, immersion time and reactant concentrations have been investigated. In addition, 3,4-dihydroxybenzoic acid and isonicotinic acid were also used to study the effect of surface functionality. Our primary results indicate that large, oriented crystalline domains could be formed on both surfaces independent of the functionality type. Benefiting from their large crystalline domains, films grown on modified surfaces exhibit higher thermal and water stability in comparison with the film grown on a bare surface.

Co-crystallization among isomeric pyridinecarboxylic acids and amides was executed towards the understanding of the formation of cocrystals and eutectics in structurally related molecules. Cocrystals have formed for all amide–amide combinations (picolinamide–nicotinamide and picolinamide–isonicotinamide, with an already known nicotinamide–isonicotinamide cocrystal) and eutectics have formed for all acid–acid combinations (picolinic acid–nicotinic acid, picolinic acid–isonicotinic acid and nicotinic acid–isonicotinic acid). Among the acid–amide combinations, all three amides form cocrystals with picolinic acid, whereas only eutectics are generated with nicotinic acid and isonicotinic acid, respectively. The contest between homomeric and heteromeric interactions and the influence of the anti-NH carboxamide group in the manifestation of different adducts for varied combinations are outlined.

We present a series of remarkable structural transformations for a family of layered metal–organic frameworks (MOFs) in a three-step solid-state reaction cycle. The cycle represents new dynamic behavior of 2D coordination polymers and involves the sequence of reactions: {[Mn2(ina)4(H2O)2]·2EtOH}n (JUK-1) → {(NH4)2[Mn(ina)2(NCS)2]}n·xH2O (JUK-2) → {[Mn2(ina)2(Hina)2(NCS)2]}n (JUK-3) → JUK-1 (Hina = isonicotinic acid), each accompanied by rearrangement of intralayer coordination bonds and each induced by a different external stimulus. In situ investigation of the first step of the cycle by combined synchrotron X-ray diffraction and Raman spectroscopy reveals direct mechanochemical unzipping of JUK-1 bilayers to respective JUK-2 layers with reaction rates dependent on the milling conditions. In contrast, the reverse zipping of JUK-2 layers involves two steps and proceeds through a new MOF (JUK-3) whose structure was elucidated by powder X-ray diffraction. Magnetic measurements confirm conversions of manganese nodes in the reaction cycle. The findings indicate the possibility of developing coordination-based assemblies with large structural responses for use in smart stimuli-responsive systems and sensor technologies.

Two new series of two-dimensional (2-D) lanthanide–silver heterometallic–organic frameworks with the formula [Ln2Ag(IN)2(BPDC)2(H2O)4]·(NO3)·2H2O (1-Ln) (Ln = Nd 1, Eu 2, Tb 3, and Dy 4) and [Ln2Ag(IN)2(BPDC)2(H2O)2]·(NO3)·2H2O (2-Ln) (Ln = Ho 5, Yb 6, HIN = isonicotinic acid, H2BPDC = 2,2′-biphenyldicarboxylic acid) have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD). In the structures of these six compounds, BPDC2− ligands link Ln3+ through their carboxylate groups, resulting in the formation of one-dimensional (1-D) {Ln(BPDC)}n infinite chains. These adjacent chains are further connected to each other via the coordination interaction between Ln3+ and carboxylate groups of IN− ligands, as well as the pillared Ag(IN)2 units, giving rise to 2-D layered structures. Although they have similar secondary building units (SBUs), the whole open frameworks of these two types of HMOFs that may be produced by the lanthanide contraction effect are quite different. Isostructural compounds 1–4 (1-Ln) crystallize in the monoclinic C2/c space group and possess a (6,3)-connected topology containing 1-D hexagonal microporous channels along the c axis, while isostructural compounds 5 and 6 (2-Ln) crystallize in the triclinic P space group and present a 2-D network of (4,4)-connected topology with 1-D rhombic channels along the b axis. Meanwhile, solid-state photoluminescence studies of compounds 1–3 and 6 were also conducted at room temperature and the luminescence intensity of 3 and 6 are found to be sensitive to small molecules.

Crystal polymorphism is the capacity of a crystalline solid to exist in more than one structural arrangement. The variation in the crystalline forms often induces different mechanical, thermal, and chemical properties. These changes can markedly influence the bioavailability, hygroscopicity, stability and other performance characteristics of the active pharmaceutical ingredient. Isoniazid, a well-known pharmaceutical, is used as a first-line treatment against Mycobacterium tuberculosis (TB). Derivatives of isoniazid were developed in response to TB drug resistance. One such derivative synthesized, isonicotinic acid (E)-(1-phenylethylidene)hydrazide (IPH), was found to exhibit complex polymorphic behaviour. To date, only one crystal structure of IPH has been reported in the literature. We have discovered and isolated an additional five polymorphs of IPH from various crystallization techniques, namely slow cooling, rapid evaporation, sublimation, as well as from hot-stage experiments. All of the polymorphs display hydrogen bonding through the carbonyl acceptor and hydrazide donor. Structural information about the polymorphs was obtained by single crystal and powder diffraction, while characterisation included infrared spectroscopy and Raman spectroscopy. The thermal properties of these polymorphs were also investigated using differential scanning calorimetry and hot stage microscopy.

Seven zinc and cadmium coordination frameworks, {[Zn2(TE)2]·H2O} (1a); {[Cd2(TE)(SO4)(OH)(H2O)]} (1b); TE = 2-(1H-tetrazol-5-yl)-ethanol, {[Zn1.5(TA)(INA)]·4H2O} (2a); {[Cd4.5(TA)3(N3)(OH)2(H2O)2]·H2O} (2b); {[Zn(MT)(INA)]·H2O} (2c); TA = (1H-tetrazol-5-yl)-acetic acid, MT = 5-methyl-tetrazole, INA = isonicotinic acid, {[Cd(BTMA)]·H2O} (3a); [Cd2(TTMA)(OH)] (3b); BTMA = bis-(1H-tetrazol-5-ylmethyl)-amine; TTMA = tris-(1H-tetrazol-5-ylmethyl)-amine, were obtained through in situ tetrazole synthesis and have been structurally characterized by single crystal and powder X-ray diffraction, as well as elemental analyses, FT-IR spectroscopy and thermal studies. Interestingly, by varying the reaction conditions of hydrothermal synthesis, the unprecedented in situ generation of TA and MT for 2 based on cyanoacetamide or BTMA and TTMA for 3 based on iminodiacetonitrile was observed, respectively. Compound 1a represents a very interesting example of three-dimensional (3D) frameworks containing hexagonal channels and meso-helical chains (P + M) alternately trapped by Zn–TE coordination interactions; compound 1b possesses a two-dimensional (2D) layered structure constructed from infinite organic chains and sulfate anions. Compounds 2a and 2b both crystallize in 3D frameworks containing infinite rod-shaped SBUs; compound 2c displays a two-fold diamondoid network constructed by the interconnection of Zn–MT–INA honeycomb layers and INA ligands. Compound 3a shows a 3D framework consisting of cyclic [Cd2(BTMA)2] dimer subunits, possessing an 8-connected network topology. Compound 3b shows a 3D binodal (4,8)-connected net based on tetranuclear [Cd4O2] polyoxometalates (POMs) as nodes. Furthermore, the luminescence properties of these compounds were investigated. Notably, compound 1b crystallizes in an acentric space group representing significant second harmonic generation (SHG) efficiencies.

Crystallization of three diterpenoid isosteviol derivatives with a structural fragment of isoniazid (isonicotinic acid hydrazide) and its isomers – hydrazides of nicotinic and picolinic acids (structures 5, 6 and 7 respectively) was studied by single-crystal and powder XRD. These homochiral compounds crystallize in “Sohnke” space group P21 with two independent molecules. In crystals 5 and 6, an infinite H-bonded chain of alternating molecules A and B formed by N–H⋯OC interaction is observed, while only pairwise the same interactions between molecules A and B are realized in crystal 7. In the H-bonded associates of both types, the local (non-crystallographic) mirror-symmetry of nitrogen containing substituents in molecules A and B is observed. Such type of crystal packing – H-bonded chains or dimers formed by the N–H⋯OC interaction through the glide plane – is the most typical packing in achiral compounds with a structural fragment of isoniazid and its isomers, as the CCDC analysis showed. Thus, structures 5–7 represent an interesting example of transferring a robust supramolecular mirror-symmetry motive from a racemic environment into a homochiral one, but inclusion of an “extra” molecule in a unit cell is the crystallographic “cost” of such transfer.

By control of the in situtetrazole ligand reaction and by the addition of different secondary ligands such as 2,2′-bipy, 4,4′-bipy or INA, five interesting frameworks, namely, Cd(tza)(2,2′-bipy)·H2O (1), [Cd2(btm)2(2,2′-bipy)2]·2.24H2O (2a), [Zn2(btm)2(2,2′-bipy)2]·3H2O (2b), Cd(btm)(4,4′-bipy)1/2 (3), [Zn(5MT)(INA)]2·2H2O (4) and Mn2(btm)2(2,2′-bipy)2 (5) (H2tza = 1H-tetrazolate-5-carboxylate; bipy = bipyridine; H2btm = bis(tetrazole) methane; 5MT = 5-methyl-tetrazole; HINA = isonicotinic acid), were synthesized and structurally characterized by single-crystal X-ray diffraction. Compound 1 exhibits a two-dimensional (2D) framework constructed of the dinuclear [Cd2O2] clusters and μ3-κN4:κN6,O1:κO1 bridging tza. Compounds 2a and 2b display 2D frameworks built up by the linkage of infinite one-dimensional (1D) helical zigzag -M-btm-M- chains (M = Cd, Zn, respectively) with dinuclear units [MN2]2.. Compounds 1, 2a and 2b all exhibit a 2D four-connected (4,4) topological network. Compound 3 represents a three-dimensional (3D) framework constructed of 2D layers formed by the linkage of [Cd2N4] cluster units and μ4-κN2:κN4:κN8:κN1, N5 tetrazolate groups as 'double-bridges', which are pillared through 4,4-bipy, finally giving a pcu (412 63) topology. Compound 4 exhibits a 3D two-fold interpenetrating diamond-like network constructed by infinite -5MT-Zn-5MT- chains and INA as bridging coligands. Compound 5 is a 2D framework which is built up by Mn1-tetrazole helical chains, [Mn2N2]2 clusters and μ3-κN11:κN14, N15:κN17 and μ3-κN3, N7:κN4:κN10 tetrazole groups. It is noted that both H2tza and H2btm ligands are in situ generated from the same precursor, malononitrile. These results show the influence of the reactant ratio, the nature of the secondary ligands and the metal ions in the construction of metal frameworks based on tetrazole. The photoluminescent properties of 1, 2a, 2b, 3, 4 and thermal stabilities of 1, 3, 4, 5 are investigated in the solid state at room temperature.

The anti-tuberculosis molecule isonicotinic acid hydrazide (isoniazid) is a promising molecule in the supramolecular synthesis of multi-component molecular complexes and also allows for its biological activity to be improved and modified by a simple covalent reaction. The low temperature crystal structures of both isoniazid (1) and the related N′-(propan-2-ylidene)isonicotinohydrazide molecule (2), the latter known to be a more effective agent against Mycobacterium tuberculosis, are reported. In addition, these two molecules were then co-crystallized with the same three Generally Regarded As Safe (GRAS) molecules, succinic acid, 4-hydroxybenzoic acid and 2-hydroxybenzoic acid, to produce the following pharmaceutical co-crystals: (isonicotinic acid hydrazide)2·(succinic acid) 3, (N′-(propan-2-ylidene)isonicotinohydrazide)2·(succinic acid) 4, (isonicotinic acid hydrazide)·(4-hydroxybenzoic acid) 6, (N′-(propan-2-ylidene)isonicotinohydrazide)·(4-hydroxybenzoic acid) 7, (isonicotinic acid hydrazide)·(2-hydroxybenzoic acid) 8, and (N′-(propan-2-ylidene)isonicotinohydrazide)·(2-hydroxybenzoic acid) 9. In addition, a co-crystal using 2-butanone as a modifier is also reported, (N′-(butan-2-ylidene)isonicotinohydrazide)2·(succinic acid) 5. Drug–drug co-crystals were also made with the anti-HIV compound 2-chloro-4-nitrobenzoic acid: (isonicotinic acid hydrazide)·(2-chloro-4-nitrobenzoic acid) 10, and (N′-(propan-2-ylidene)isonicotinohydrazide)·(2-chloro-4-nitrobenzoic acid) 11. All the co-crystals use the carboxylic acid⋯pyridine hydrogen bond to connect the GRAS or drug molecule to the pyridine ring. In general, the co-crystals with the modified isoniazid feature the C(4) homosynthon, and those with the original isoniazid a variety of homo- and heterosynthons. By comparing the melting points of the co-crystals that use isoniazid and those that use the modified isoniazid, a reduction in melting point is observed.

Different series of Ln(III)–Ag(I) heterometallic coordination frameworks, namely LnAg(OAc)(IN)2(H2O)·(ClO4) [Ln = Tb (1a); Ho (1b), HOAc = acetic acid, HIN = isonicotinic acid], LnAg2(OX)0.5(IN)3(H2O)1.5·(ClO4) [Ln = Nd (2a); Eu (2b) Tb (2c), OX = oxalate], Eu2Ag3(OX)0.5(IN)6(NO3)(ClO4)(H2O)3·2(H2O) (3), LnAg(OX) (IN)2(H2O) [Ln = Ce (4a); Sm (4b)], LnAg(Mal)(IN)2(H2O) [Ln = La (5a); Nd (5b), H2Mal = malonic acid], Ln3Ag4(Lac)2(IN)8(H2O)5·2(ClO4)·2.5(H2O) [Ln = La (6a); Lu (6b), HLac = lactic acid], Sm3Ag4(Lac)2(IN)8(H2O)4·2(ClO4)·2.5(H2O) (7), and Eu2Ag3(S-Lac)(IN)6(H2O)4·2(ClO4)·4(H2O) (8) were successfully synthesized by systematic variation of reaction parameters such as initial reactants, reaction time, pH, temperature, etc. Compounds 1a and 1b represent 3D coordination frameworks that are constructed from adjacent lanthanide carboxylate layers and pillared Ag(IN)2 units. Compounds 2a, 2b and 2c comprise of 2D Ln-carboxylate-Ag layered networks and pillared Ag(IN)2 units. Compound 3 exhibits 3D coordination frameworks that are built up from the assembly of europium-carboxylate layers and pillared Ag(IN)2 units. 3D coordination networks of compounds 4a and 4b containing tetranuclear Ln2Ag2 cores are constructed from 2D cerium oxalate layers and tilted pillared Ag(IN)2 subunits. Compounds 5a and 5b display attractive 3D coordination frameworks constructed of 2D lanthanum malonate chains and pillared Ag(IN)2 units. Compounds 6a and 6b are 2D coordination frameworks comprised of 1D racemic lanthanum carboxylate chains and pillared Ag(IN)2 units. The crystal structure of 7 is almost the same as that of 6a and 6b, only one less coordination water molecule is coordinated to its metal centre. Compound 8, which spontaneously resolved upon crystallization, represents the first example of a 3D Ln–Ag coordination framework built up from 1D europium-carboxylate chains containing chiral molecules and pillared Ag(IN)2 units.

A series of metal–organic supramolecular co-ordination polymers [Zn(HPO4)(Hpytz)] (1), [Cd(Hpytz)2(H2PO4)2(H2O)2] (2), [Zn(pytz)2(H2O)4]·2H2O (3) [pytz− = 5-(4-pyridyl)tetrazolate], [M(tzpyo)2(H2O)4] [M = Zn (4), Ni (5)] [tzpyo− = 4-tetrazolate-pyridine N-oxide] incorporating tetrazolyl ligands have been synthesized via in situ [2 + 3] cycloaddition reactions of 4-cyanopyridine, 4-cyanopyridine N-oxide with sodium azide in the presence of zinc, cadmium or nickel salts under hydrothermal reaction conditions at 130–160 °C. Use of higher temperatures leads to hydrolysis of nitriles to carboxylates and subsequently to decarboxylation, resulting in two unexpected byproducts, [inaH]+(NO3−) (6) [ina = isonicotinic acid] and [(4,4′-bipyH2)(H2PO4)2(H2O)2] (7). Single crystal X-ray structure analyses of 1 and 2, prepared under hydrothermal conditions in the presence of H3PO4, reveal κ1-co-ordination of the N-donor at the 2-position of the tetrazolyl ligands binding in a TZ-mode. The pyridyl N-centres in 1 and 2 are protonated resulting in the formation of Npy–H⋯O hydrogen-bonds within the solid-state structures. In the absence of H3PO4 similar hydrothermal reactions afforded 3, in which the pyridyl group is directly bound to Zn(II) and tetrazolate-ring is unco-ordinated (PY-mode). Single crystal X-ray structures of 4 and 5 show a TZ-binding mode analogous to that for 1 and 2, with the pyridyl N-oxide moiety forming hydrogen-bonds with co-ordinated water molecules to give supramolecular pillar-layered frameworks. Complex 2 exhibits a distorted 6-connected α-Po net of 412·63 topology; 3 possesses an attractive 3D (4,5,10)-connected trinary (3·42·53)2(3·44·54·6)4(32·48·514.612·77·82) net, while the isostructural complexes 4 and 5 show 3D (4,8)-connected layer-pillared network structures with a unique (46)2(412·612·84) topology. In 6, all hydrogen atoms of inaH+ cations are involved in the formation of hydrogen-bonds with either nitrate or other inaH+ cations resulting in a 2D (4,6)-connected binary net with (32·42·52)(34·44·54·63) topology. In 7, the dihydrogenphosphate anions are arranged viahydrogen-bonds into an unusual (4,4) grid-type sheet, and these layers are further pillared by organobipyridine cations to form a 3D open framework with channels occupied by helical chains of water dimers. The thermal stability of these metal-tetrazolate complexes has been studied by TGA and powder X-ray diffraction, and the effect of proton source (H3PO4) on the co-ordination mode of these tetrazolyl ligands is discussed.

Four novel 4d–4f heterometallic coordination polymers, namely, LnAg(pydc)2(Hnic)0.5 [Ln = Nd (1), Eu (2); H2pydc = pyridine-3,4-dicarboxylic acid, Hnic = nicotinic acid], and LnAg(inic)2(nicO)·0.5H2O [Ln = Nd (3), Eu (4); Hinic = isonicotinic acid, H2nicO = 2-hydroxynicotinic acid], have been synthesized and characterized. Compounds 1 and 2 exhibit three-dimensional (3-D) coordination frameworks constructed by one-dimensional (1-D) inorganic heterometallic chains and linear pydc linkers. The 1-D channels occupied by disordered Hnic molecules emerge. To our knowledge, both compounds represent the first examples of 3-D open-framework 4d–4f heterometallic coordination frameworks. Compounds 3 and 4 display 3-D covalent frameworks composed of 1-D inorganic heterometallic chains joined by inic ligands, representing the first examples of 3-D 4d–4f coordination frameworks constructed by inorganic heterometallic chain and mixed linear and nonlinear ligands with same donors. Furthermore, the luminescent properties of 2 and 4 were studied.

The crystal structures of the three isomers of the chemically labile pyridinecarboxylic acid chloride hydrochlorides were analyzed in order to study the weak interactions of the chloride anion with hydrogens. The chloride anions in the crystal structure of 1a have a slightly distorted square-planar interaction sphere with four hydrogens in the equatorial plane (plane of the molecule) with Cl−⋯H distances varying from 2.041(1) A [NH+⋯Cl−] to 2.933(1) A [CH⋯Cl−]. Nicotinic and isonicotinic acid chloride hydrochloride 1b and 1c show that chloride anion has a crucial role in the formation of bridged dimeric structures. The crystal lattices of 1b and 1c manifest similar herring-bone packing patterns. The chloride anions of 1b and 1c have slightly deformed planar interaction geometries to five and six hydrogens, respectively, with Cl−⋯H distances varying from 2.334(1) and 2.385(4) A [NH+⋯Cl−] to 2.781(3) and 2.833(6) A [CH⋯Cl−] in 1b and 1c, respectively. The difference in the packing of the isomers was attributed to Cl−⋯C contacts in 1a and on the other hand to end-to-end intermolecular interactions of the dimers of 1b and 1c, which could not exist with herring-bone packing of 1a. The moisture sensitive crystals of 1a, 1b, and 1c were obtained by sublimation of the compounds by heating in vacuo.

The hydrothermal reaction of rare earth nitrates, CuCN, 1H-1,2,3-triazole-4,5-dicarboxylic acid (H3tda), and isonicotinic acid (Hina) resulted in the formation of a new series of 3d–4f heterometallic coordination polymers [LnCu(tda)(ina)2(H2O)]·3H2O (Ln = Eu (1), Tb (2), Gd (3), Dy (4), Ho (5)], H3tda = 1H-1,2,3-triazole-4,5-dicarboxylic acid, Hina = isonicotinic acid). Complexes 1–5 are isostructural and structurally characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric analysis (TGA), and single-crystal powder X-ray diffraction (PXRD). Single-crystal X-ray diffraction analysis reveals that the metal cations in these compounds are firstly interconnected by H3tda ligands to produce a carpet-shaped heterometallic ring [Ln2(tda)2Cu4], and then pillared by bridging Hina molecules to form the 3D layer-pillared porous Ln(III)–Cu(II) heterometallic coordination polymers. In addition, the magnetic properties of 1–5 were also investigated in detail.

By variation of reaction parameters such as metal salts and secondary ligands, a series of new coordination polymers, [Cd(QTZ)2] (1), [Cd(QTZ)N3·H2O] (2), [Zn(QTZ)Cl] (3), [Cd2(QTZ)2(INA)2]·0.25H2O (4), [Cd2(QTZ)(btrc)·2(H2O)]·1.67H2O (5), 2[Cd3(QTZ)2(btec)·H2O]·H2O (6) (QTZ = 5-(quinolyl)tetrazole; HINA = isonicotinic acid; H3btrc = 1,3,5-benzenetricarboxylic acid; H4btec = 1,2,4,5-benzenetetracarboxylic acid) were successfully synthesized under hydrothermal reactions and structurally characterized by single-crystal X-ray diffraction. The QTZ ligands in these compounds are in situ generated from a [2 + 3] cycloaddition reaction of 3-quinolinecarbonitrile and NaN3 in water with the acid of CdII/ZnII salt. Compound 1 displays a three-dimensional (3D) 2-fold interpenetrating diamond network with Schlafli symbol 66. Compound 2 represents a two-dimensional (2D) coordination framework constructed of infinite Cd–N3− chains and QTZ ligands. Compound 3 exhibits a 4-connected 2D (4,4) net built up by interconnection of Zn2(QTZ)2Cl2 subunits. Compound 4 is a 2D framework constructed by interconnection of Cd2(QTZ)2(INA)2 subunit and Cd2(QTZ)2 subunit. Compound 5 exhibits a 2D layered structure with the Cd2–QTZ chain extended by btrc ligands. In compound 6, trinuclear CdII clusters link each other by pairs of QTZ ligands to form an infinite zigzag Cd3–QTZ chain; furthermore the adjacent Cd3–QTZ chains are extended by the btec ligands to form a 3D network. These results indicate that QTZ is a powerful functional ligand and the nature of secondary ligands and transition metal ions also play significant roles in dominating molecular self-assembled structure. In addition, the luminescent properties of all compounds have been investigated in the solid state at room temperature.

A new Co(II)-based coordination polymer, [{Co3(ina)7.5(μ3–O)}{Co3(ina)2.5(μ3–OH)(μ–OH)(C2H5OH)(H2O)2}3]NO3·3C2H5OH·24H2O (1, also denoted as MCF-39), has been synthesized from the solvothermal reaction of cobalt(II) nitrate and the ligand isonicotinic acid (Hina) with the presence of hmq (2-(hydroxymethyl)-quinolin-8-ol) as a necessary additive. The crystal structure of 1 consists of the 7- and 9-connected trinuclear clusters, and exhibits the first highly-connected binodal network with (34·49·56·62)3(36·415·515) topology. Magnetic studies show that the spin canting and spin-glass-like behaviours were found in 1, and the cooperative effect among intra- and inter-trimer could greatly influence the bulk magnetic behaviour of the three-dimensional (3D) framework.

Using a small planetary ball mill, liquid-assisted grinding (LAG) of metal salts or oxides (ZnO, CdO, CdCO3, Cu(OAc)2·H2O, Co(OAc)2·4H2O, Mn(OAc)2·4H2O, Ni(OAc)2·4H2O, FeSO4·7H2O) with two equivalents of isonicotinic acid (HINA) and small amounts of water (up to 5.6 molar equivalents) gave discrete aquo complexes trans-[M(INA)2(OH2)4] (M = Zn, Cd, Cu, Fe, Co, Ni, Mn) efficiently within 30 min. For M = Zn, Cd and Cu these complexes readily undergo reversible formal dehydration to the extended network structures [M(INA)2] (M = Zn, Cu) or [Cd(INA)2(OH2)]·DMF by further LAG with non-aqueous liquids such as methanol or DMF. Overall, the mechanochemical dehydrations are more effective than heating or immersion in bulk solvents. The work demonstrates a two-step mechanochemical synthesis of coordination networks via discrete aquo complexes which may be preferable to single step reactions or grinding-annealing procedures in some cases. For example, the two step method was the only way to prepare [Cd(INA)2(OH2)]·DMF mechanochemically and the porous network Cu(INA)2 could not be obtained from the aquo complex by heating.

Nine 3D heterometallic coordination polymers, namely [NaLn2Cu6I5(IN)6(ox)(H2O)4]·H2O [Ln = La (1), Eu (2), Gd (3), Tb (4), HIN = isonicotinic acid, ox = oxalate], [Ln2Ag4(IN)5(ox)2(NO3)(H2O)2]·3H2O [Ln = Dy (5), (6) Ho], [LnAg(IN)2(ox)]·H2O [Ln = La (7), Pr (8), Tm (9)] have been successfully synthesized under hydrothermal conditions. Compounds 1–4 exhibit same unusual 3D pillared-layer heterometallic coordination frameworks that are built up by the Ln-ox-Na layers, 2D inorganic [(Cu6I5)+]n layers and IN ligands. Compounds 5 and 6 represent 3D coordination frameworks that are constructed from rare Ln(III)-ox-IN chains and Ag(I)-IN-ox layers. 3D coordination networks of compounds 7–9 are built up from 2D Ln(III)-IN-ox layers and Ag(I)-IN-ox subunits. Furthermore, the magnetic properties of compounds 5 and 6 and the luminescence properties of compounds 2, 4 and 5 have been investigated.

The synthon approach has been applied to synthesizing pharmaceutical co-crystals using the anti-tuberculosis drug isonicotinic acid hydrazide (ISONIAZID). Isoniazid has the potential to be a supramolecular reagent and so far has been put to very limited use in making co-crystals. In this report, we co-crystallize isoniazid with the dicarboxylic acids malonic (1), succinic (2), glutaric (3), adipic (4) and pimelic acid (5), and the monocarboxylic acids 4-hydroxybenzoic acid (6) and 2,4-dihydroxybenzoic acid (7). By surveying the literature through the Cambridge Structural Database, we identified the possible homosynthons and heterosynthons that are likely to form in the co-crystallization of isonizaid with carboxylic acids. The dominant interaction is the COOH⋯N hydrogen bond, which is used in all seven co-crystals. In addition, we present an example in which both a covalent and supramolecular synthesis occurs without affecting the vital supramolecular co-crystal forming synthon, the carboxylic acid⋯pyridine pair functionality, by reacting isoniazid with 2-butanone and acetone while co-crystallizing it with 3-hydroxybenzoic acid (8 and 9) in a one-pot synthesis.

Five novel 2D heterometallic coordination polymers, Ln2Cu5(ina)6(CN)5.5·4H2O [Ln = Nd (1), Eu (2), Tb (3), Gd (4), Sm (5); ina = isonicotinic acid], have been synthesized under hydrothermal conditions and characterized by elemental, infrared, thermogravimetric and X-ray diffraction analyses. These complexes are constructed of Ln2(ina)6 chains, Cu–CN–Cu, and CN–Cu–CN chains, which represent the first examples of 3D coordination compounds created by using a combination of metal–cyanide chains, lanthanide–carboxylate linear chains and O–H⋯N hydrogen bonds.

An array-based approach is put forward to obtain insight into reactivity under mechanochemical solvent-free conditions. We describe a survey of sixty potential reactions between twelve metal salts MX2 {(M = Cu, X2 = (OAc)2, (HCO2)2, (F3CCO2)2, (acac)2, (F6acac)2, (NO3)2, SO4; M = Ni, X2 = (OAc)2, (NO3)2, SO4; M = Zn, X2 = (OAc)2, (NO3)2} and five bridging organic ligands {isonicotinic acid (HINA), 1,4-benzenedicarboxylic acid (H2BDC), acetylenedicarboxylic acid (H2ADC), 1,3,5-benzenetricarboxylic acid (H3BTC), 4,4′-bipyridyl (BIPY). Reaction conditions involved a ball mill, applied for 15 min at 30 Hz, without external heating. When examined by XRPD, forty of the combinations gave detectable reactions, thirty-eight with crystalline products. Of these, twenty-nine reactions were quantitative (consuming all of at least one reactant). Comparison of XRPD patterns with patterns simulated from single crystal X-ray diffraction data in the Cambridge Structural Database allowed structural identification of six products. Of particular interest are the microporous framework materials [Cu(INA)2] and [Cu3(BTC)2] (HKUST-1) obtained by reaction of the corresponding carboxylic acids with copper acetate. Other non-porous polymers with 3-dimensional connectivity, [Ni(ADC)(H2O)4], or 1-dimensional connectivity, [Cu(acac)2(BIPY)] and [Cu(F6acac)(BIPY)] were also obtained. Reaction between zinc acetate and H2ADC gave a new product which had not previously been characterised by single-crystal X-ray crystallography, but whose XRPD pattern suggests that it is isostructural with the known nickel polymer [Ni(ADC)(H2O)4]. Two further isostructural nickel and zinc products were obtained in reactions between HINA and nickel nitrate and zinc nitrate. Trends observed within the array are discussed. Copper acetate and copper formate were the most effective starting materials for reaction with carboxylic acids, potentially related to the basicity of their anions and the solvating effects of the formic and acetic acid byproducts. Amongst the ligands there was a general negative corelation between melting point and reactivity. The issue of pore templating in microporous phases and the generation of new structures is also discussed in relation to the Cu(INA)2, Cu3(BTC)2 and nickel nitrate-BIPY systems. Overall, the study suggests that mechanochemical reactivity between metal salts and organic ligands under solvent free conditions is remarkably general. Use of array-based approaches as demonstrated here is advocated a useful way to reveal underlying trends in reactivity under solvent free mechanochemical conditions and to highlight particular cases for more detailed study.

We describe the first solvent-free mechanochemical synthesis of a microporous metal–organic framework [Cu(INA)2] (INA = isonicotinic acid); the product has robust 3-dimensional connectivity and is obtained quantitatively by grinding together copper acetate and isonicotinic acid for 10 minutes without any applied heating—the high efficiency of the synthesis suggests that mechanochemical synthesis should be further investigated as a convenient method for the preparation of microporous metal–organic frameworks (MOFs).

The reactions of isonicotinic acid analogues, 4-quinolinecarboxylic acid (HL1) and 9-acridinecarboxylic acid (HL2) with M(NO3)2 (M = ZnII and CdII) in the presence of Et3N in MeOH (or EtOH) led to the formation of four new complexes, [Zn(L1)2(H2O)]∞ (1), [Zn(L2)2(MeOH)2]3·(H2O)1.5 (2) and [Cd(L2)2(MeOH)2]3·(H2O)1.5 (3) and [Cd(L2)2(EtOH)2]3·(H2O)0.5 (4). Single crystal X-ray diffraction analyses revealed that the ZnII and CdII complexes of the same ligand (L1 or L2) are isostructural, with 1 taking a 1D chain structure, with 2–4 being trinuclear complexes. In such complexes, the carboxylate groups adopt a bidentate syn,syn-bridging coordination fashion to bridge adjacent metal centers. The N donors do not take part in the coordination, but form O–H⋯N hydrogen bonds with the coordinated water or MeOH (or EtOH), leading to the formation of 3D frameworks. The effects of π–π stacking and the structural differences between these complexes and those with isonicotinic acid were also discussed.