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A range of morphologically distinct metallosupramolecular Cu(II) and Pd(II) complexes has been constructed, based on the tritopic ligand 1,1',1″-(benzene-1,3,5-triyl)tris(4,4-dimethylpentane-1,3-dione) (H). By control of the reaction conditions, it is possible to generate distinct coordination assemblies possessing either macrocyclic or polymeric structures and more importantly distinct activity in catalysis of the Suzuki-Miyaura cross-coupling.

A spin-crossover (SCO) active dinuclear Fe(II) triple helicate of the form [Fe] was combined with additional supramolecular components in order to manipulate the interhelical separation and steric congestion and to study the magneto-structural effects on the ensuing composite materials. A more separated array of SCO units produced more extensive spin-transitions, while a tightly arranged lattice environment stabilized the low-spin state. This study highlights the important interplay between crystal packing, intermolecualr interactions, and the magentic behavior of SCO materials.

In a recent study, Dey et al.1 propose a mechanism of elastic bending in co-crystals of caffeine, 4-chloro-3-nitrobenzoic acid and methanol (1) in which mechanical interlocking is proposed to allow for the reversible flexibility observed. We have now determined the mechanism to atomic resolution using micro-focused synchrotron radiation,2 which is different to that previously reported. When subjected to strain the inter-molecular distances change and hydrogen-bonded dimers rotate over two orthogonal directions to allow the compression and expansion producing flexibility.

We probe, here, a family of 2D Hofmann-type frameworks, [FeII(Pd(CN)4)(bztrzX)2]·nH2O [X·nH2O; X = F, Cl, Br; n = 1 (X = Cl, Br) and 3 (X = F); bztrzX = (E)-1-(2-Xphen-1-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine], with halogen-appended ligands. In all cases, there are two crystallographically distinct FeII sites, ({Fe1-Fe2}), driven by the presence of a range of host-host and host-guest interactions. We find that lattice modification through X variation influences the elastic coupling between the FeII sites, the emergence of ferroelastic or antiferroelastic interactions between these sites, and the relative spin-state stabilization/destabilization at each site. In Cl·H2O, the FeII sites show strong elastic coupling, as evidenced by both FeII sites undergoing a spin transition in a single cooperative step, as driven by the volume strain over the high-spin (HS)-to-low-spin (LS) transition. The FeII sites in F·3H2O are also elastically coupled; however, the change of the X atom characteristics and increased guest molecules in the pores result in an antiferroelastic interaction characteristic between Fe1 and Fe2 and a resultant two-step spin-state transition. The change of the X atom to Br in Br·H2O results in the FeII sites being decoupled due to halogen atom steric bulk, resulting in the independent spin-state transition of Fe1 and Fe2 sites and a two-step spin-state transition pathway. Uniquely, all three possible spin-state transition pathways of a two-site switching system are observed in this family [(1) {HS-HS} ↔ {HS-LS} ↔ {LS-LS} for Br·H2O, (2) {HS-HS} ↔ {LS-HS} ↔ {LS-LS} for F·3H2O, and (3) {HS-HS} ↔ {LS-LS} for Cl·H2O for {Fe1-Fe2}]. Overall, these findings broadly support recent theoretical models but highlight that additional structural and topological complexities are needed to form a holistic picture of the drivers of elastic frustration.

The synthesis and crystal structures of a series of Ln(III) (Ln = Gd, Nd, Yb as well as Y) complexes of a bis-β-diketone ligand incorporating a 1,3-substituted phenyl ring between its two β-diketone domains (1,1′-(1,3-phenylene)bis(4,4-dimethylpentane-1,3-dione), H2L1) is reported. The crystal structures show the complexes are seven coordinate in the solid state with the general formula [Ln2L13(solvent)2]. The photophysical properties of the complexes were explored in both solution and the solid state, which show an increase in coordination number in solution.

A two-dimensional molecular square (MC) was obtained by the self-assembly of a bis(tetrazole) linker, 4,4'-bis(1H-tetrazol-5-yl)-1,1'-biphenyl (H2L1), with a square-planar metal acceptor M [M = (tmeda)Pd(NO3)2, where tmeda = N,N,N',N'-tetramethylethane-1,2-diamine] in dimethyl sulfoxide (DMSO) followed by crystallization. The uncommon 2,3-binding mode through N atoms of the tetrazole rings in this assembly leads to the formation of an octanuclear molecular square. The molecular square MC [Pd8(L1)4(NO3)8] is unstable in DMSO and slowly converts to a dynamic mixture of a 3D tetrahedral cage T1 [Pd12(L1)6(NO3)12] and the macrocycle MC. A tetrahedral cage (T1) is formed by the usual 1,3-binding mode of the tetrazole rings. However, self-assembly of the T1 [Pd12(L1)6(PF6)12] was possible to access in the pure form in a less polar solvent like acetonitrile. The pure T1 [Pd12(L1)6(PF6)12] also converts to a mixture of T1 and MC in DMSO. Interestingly, when a tris(tetrazole) linker, tris(4-(1H-tetrazol-5-yl)phenyl)amine (H3L2), was treated with the acceptor M, it produced a tetrahedral nanocage T2 [Pd12(L2)4(NO3)12] through 1,3-binding mode of the tetrazole rings without any trace of an octahedral cage through 2,3-binding mode of the tetrazole moieties.

Two Co L tetrahedral cages prepared from similar building blocks showed contrasting host-guest properties. One cage did not bind guests, whereas the second encapsulated a series of anions, due to electronic and geometric effects. When the building blocks of both cages were present during self-assembly, a library of five Co L L cages was formed in a statistical ratio in the absence of guests. Upon incorporation of anions able to interact preferentially with some library members, the products obtained were redistributed in favor of the best anion binders. To quantify the magnitudes of these templation effects, ESI-MS was used to gauge the effect of each template upon library redistribution.

Encasing the classic spin-crossover (SCO) complex cation [Co(terpy)2]2+ in different anionic supramolecular frameworks modulates its SCO behavior, tuning both its T1/2 (shift of up to 200 K) and th...

The encapsulation of metal complexes within halogen-bonded networks may lead to modulation of their properties in the solid state without the need to chemically incorporate donor or acceptor moieties on the metal complex itself. Here, we investigate the effect of anionic halogen-bonded structure formation on the organization of arene-rich bis(4′-phenyl-2,2′:6′,2″-terpyridine)nickel(II) cations, varying both the topicity and the geometry of the halogen bond donor in a heteromeric three-component system. The X-ray structures of four cocrystals (1-4), [Ni(terpy-ph)][(1,2-DITFB)(I)] (1), [Ni(terpy-ph)][(1,3-DITFB)(I)] (2), [Ni(terpy-ph)][(1,4 DITFB)(I)](I)·9HO (3), and [Ni(terpy-ph)][(1,3,5-TITFB)(HO)(I)]·2HO (4), as well as the iodide salt of the parent complex [Ni(terpy-ph)]I·4HO are reported along with characterization to assess bulk sample and phase purity. Within assemblies of complex cations, we observe the ubiquitous aryl embrace motif often seen in the crystal packing of such terpyridine complexes; however, these assemblies are separated from one another by a variety of halogen-bonded structures, including discrete supramolecular complexes, 1D chains, pseudo-2D sheets, and unusual racemic double helices. The results herein demonstrate how typical crystal packing motifs of metal terpy-ph complexes can be altered and disrupted through their incorporation into halogen-bonded heteromeric three-component systems.

In this study, a hydroxyl-rich Schiff base ligand, H4L, and its resulting complexes with ZnCl2, Zn(CH3COO)2 and Zn(ClO4)2 were explored. Interestingly, depending on the zinc salt and/or the crystallisation method, four unique structures were obtained. A synthesis with ZnCl2 gave 1, a mononuclear structure ((H3L)2Zn), while with Zn(CH3COO)2, a trinuclear system [(H3L)2Zn3(CH3COO)4], 2, was found. Interestingly two multinuclear architectures were observed with Zn(ClO4)2. Firstly, diethyl ether diffusion of a methanolic reaction mixture with minimal atmospheric air volume gave 3, a hexanuclear architecture of the type [(H2L)4(H3L)2Zn6](ClO4)2, while slow evaporation of a similar mixture gave 4, a nonanuclear architecture with the formula [(H2L)6Zn9(CO3)2](ClO4)2. Compound 4 unexpectedly fixed atmospheric CO2 as CO32−, incorporating it into the architecture. As expected, a diethyl ether diffusion with a larger volume of air (∼100 mL) of a similar methanolic reaction mixture gave a mixture of 3 and 4. In addition, bulk samples of all compounds were also investigated by PXRD, and results are in good agreement with the observed single crystal data. Furthermore, complexes 1–4 were characterised using FT-IR and simultaneous thermal analysis (STA), and additionally the photophysical properties of H4L and complexes 1–4 have also been explored.

A bis-β-diketone ligand incorporating a 3,5-substituted pyridine ring between its two β-diketone domains (1,1′-(pyridine-3,5-diyl)bis(4,4-dimethylpentane-1,3-dione), H2L1) and its interaction with three divalent cations (Cu2+, Zn2+ and Pd2+) is reported. Charge neutral dinuclear metallocycles of type [M2L12] were obtained in each case and their X-ray structures determined. [Pd2L12] incorporates two square-planar O4-coordinated metal centres. The zinc(II) and copper(II) complexes contain five-coordinate O4N1-metal centres in which the pyridyl nitrogen from adjacent [M2L12] metallocycles coordinates apically forming two-dimensional coordination polymers of type {[Zn2L12]n(dmf)n} and {[Cu2L12]n(dmf)n}. Desolvation of the coordination polymers led to loss of crystallinity.

An extended nitro-functionalised 1,2,4-triazole ligand has been used to induce considerable lattice distortion in a 2-D Hofmann framework material via competing supramolecular interactions. Single crystal X-ray diffraction analyses on [Fe3(N-cintrz)6(Pd(CN)4)3]·6H2O (N-cintrz: (E)-3-(2-nitrophenyl)acrylaldehyde) reveal a substantial deviation from a regular Hofmann structure, in particular as the intra- and inter-layer contacts are dominated by hydrogen-bonding interactions rather than the typical π-stacking arrays. Also, the 2-D Hofmann layers show an assortment of ligand conformations and local FeII coordination environments driven by the optimisation of competing supramolecular contacts. Temperature-dependent magnetic susceptibility measurements reveal a two-step spin crossover (SCO) transition. Variable temperature structural analyses show that the two crystallographically distinct FeII centres, which are arranged in stripes (2 : 1 ratio) within each Hofmann layer, undergo a cooperative HS ↔ HS/LS ↔ LS (HS = high spin, LS = low spin) transition without periodic spin-state ordering. The mismatch between crystallographic (2 : 1) and spin-state (1 : 1) periodicity at the HS : LS step provides key insight into the competition (frustration) between elastic interactions and crystallographically driven order.

The effect of halogen functionalization on the spin crossover (SCO) properties of a family of 2-D Hofmann framework materials, [FeIIPd(CN)4(thioX)2]·2H2O (X = Cl and Br; thioCl = (E)-1-(5-chlorothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine) and thioBr = (E)-1-(5-bromothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine)), is reported. Inclusion of both the chloro- and bromo-functionalized ligands into the Hofmann-type frameworks (1Cl·2H2O and 2Br·2H2O) results in a blocking of spin-state transitions due to internal chemical pressure effects derived by the collective steric bulk of the halogen atoms and guest molecules. Cooperative one-step SCO transitions are revealed by either guest removal or the application of external physical pressure. Notably, removal of solvent water reveals a robust framework scaffold with only marginal variation between the solvated and desolvated structures (as investigated by powder and single crystal X-ray diffraction). Yet, one-step complete SCO transitions are revealed in 1Cl and 2Br with a transition temperature shift between the analogues due to various steric, structural, and electronic considerations. SCO can also be induced in the solvated species, 1Cl·2H2O and 2Br·2H2O, with the application of physical pressure, revealing a complete one-step SCO transition above 0.62 GPa (as investigated by magnetic susceptibility and single crystal X-ray diffraction measurements).

All 21 [n]-azacubanes are proposed by theoreticians to be stable, however, to-date only the synthesis of 1,4-diazacubane has been reported - as a Ni2+ templated Kagome metal organic framework (MOF). Described herein is the structural reassignment of this Kagome MOF on the basis of deducing the precise experimental procedure, and demonstrating that rather than the formation of 1,4-diazacubane, charge is balanced by disordered piperazinium cations across a twelve-fold symmetry site. Furthermore, quantum chemical calculations reveal that 1,4-diazacubane is unlikely to form under the reported conditions due to unfavorable enthalpies for select hypothetical reactions leading to such a product. This significant structure correction upholds the unconquered synthesis status quo of azacubane.

A re-refinement of the published but chemically implausible, crystal structure of “Form III” of 4-bromophenyl 4-bromobenzoate shows that it is not a polymorph, but instead a co-crystal containing both 4-bromophenyl 4-bromobenzoate (≈25%) and likely 4-bromophenyl 4-nitrobenzoate (≈75%).

A unique pressure-induced Cu-N bond breaking/bond forming reaction is reported. The variation of pressure on a single crystal of a one-dimensional copper(II)-containing coordination polymer (Cu2L2(1-methylpiperazine)2]n, where H2L is 1,1'-(1,3-phenylene)-bis(4,4-dimethylpentane-1,3-dione)), was monitored using single crystal X-ray diffraction with the aid of a diamond anvilcell. At a very low elevated pressure (~0.05 GPa) a remarkable reversible phase change was observed. The phase change results in the depolymerization of the material through the cleavage and formation of axial Cu-N bonds as well as “ring flips” of individual axially coordinated 1-methylpiperazine ligands. Overall, thepressure-induced phase change is associated with a surprising (and non-intuitive) shift in structure – from a 1-dimensional coordination polymer to a discrete dinuclear complex.

A mononuclear iron(II) complex that displays a gradual two-step spin-crossover (SCO) transition is reported. The intermediate plateau (IP) occurs between HS0.40LS0.60 and HS0.30LS0.70 (HS = high spin; LS = low spin) ratios over the region of ca. 190–170 K. A phase change occurs at the IP, breaking the symmetry, resulting in six independent SCO sites compared to one at the 100% HS and LS plateau regions, respectively. Variable-temperature X-ray photoelectron spectroscopy shows that the SCO behavior is completely reversible among the HS, IP, and LS regions. The results both confirm and extend the related results for the above system described by Halcrow et al. (KulmaczewskiR.; CespedesO.; HalcrowM. A.Gradual Thermal Spin-Crossover Mediated By a Reentrant Z′ = 1 → Z′ = 6 → Z′ = 1 Phase Transition, Inorg. Chem. 2017, 56, 3144−314828244751) in a recent report.

Zero in-plane thermal expansion (TE) in a two-dimensional (2D) coordination polymer is demonstrated. The combination of components that expand and those that shrink into zigzag layers results in no net area change in the 2D materials with temperature. Single crystals of [Mn(salen)]2[Mn(N)(CN)4(guest)] (salen = N,N′-ethylenebis(salicylideneaminato), guest = MeOH and MeCN) were prepared, and variable-temperature single-crystal X-ray structural analyses demonstrated that these compounds exhibited both anisotropic positive and negative thermal expansion depending on the guest species. The TE behavior results from distortions of the octahedral coordination geometry of [Mn(salen)]+ units in the zigzag layers. When both guests MeOH and MeCN were incorporated into one material, [Mn(salen)]2[Mn(N)(CN)4(MeOH)0.25(MeCN)0.75], zero in-plane TE resulted in a range of temperature between 380 and 440 K.

This paper presents the synthesis of a tripodal ligand (H3L) via the Schiff base condensation of N,N-diethylsalicylaldehyde and tris(2-aminoethyl)amine. The neutral complexes of type [EuL], [GdL] and [DyL] were synthesized and characterized by FT-IR, SEM-EDS, PXRD, single crystal X-ray diffraction, CHN analysis and high resolution ESI-MS. X-ray crystallographic studies demonstrated that the heptadentate ligand incorporating a cavity pre-organized by hydrogen bonding binds the Ln(iii) ions to yield a face capped octahedral coordination geometry with three-fold symmetry. Photoluminescence studies show a typical Ln(iii) absorption character for the three complexes, with [EuL] demonstrating considerably stronger lanthanide-based luminescence peaks, and a Eu(iii) centered luminescence lifetime of 0.144 ± 0.01 ms. Temperature/field-dependent DC and temperature/frequency-dependent AC magnetic measurements carried out for the Dy(iii) complex indicated obvious magnetic anisotropy and suggested slow relaxation behaviour with considerable quantum tunnelling of the magnetization contribution.

A series of Fe(III) complexes of β-diketonate ligands, 1-(2-pyridyl)-3-(3-pyridyl)-1,3-propanedione (L1), 1-(2-pyridyl)-3-(2-pyridyl)-1,3-propanedione (L2), 1-(2-pyridyl)-3-(4-pyridyl)-1,3-propanedione (L3), 1-(3-pyridyl)-3-(4-pyridyl)-1,3-propanedione (L4), 1-(3-pyridyl)-3-(3-pyridyl)-1,3-propanedione (L5) and 1-(4-pyridyl)-3-(4-pyridyl)-1,3-propanedione (L6), viz. [Fe(L1)3] (1), [Fe(L2)3] (2), [Fe(L3)3] (3), [Fe(L4)3] (4), [Fe(L5)3] (5) and [Fe(L6)3] (6) have been structurally characterized. All but one complex (1) catalyzed the ring-opening polymerization (ROP) of e-caprolactone (e-CL) in near quantitative yield at 110 °C to give polymers with relatively narrow polydispersities (PDI). The comparison of in situ reaction and a reaction with preformed 1 indicated that the latter was a better catalyst, giving a higher molecular weight. Complex 2 catalyzed this reaction in a more modest yield reflecting its greater thermal stability, shorter Fe–O bonds and minimal distortion in fold angle among the isomeric complexes, suggesting that ligand dissociation is important for catalytic activity.

The rational, deliberate design of supramolecular architectures is of great importance for the discovery of complex materials. A three-dimensional cubic halogen-bonded network has been prepared by combination of an octahedral metal-containing halogen bond acceptor and a linear ditopic donor. This material displays α-Po pcu topology and is seven-fold interpenetrated. This is the first neutral, metal-containing three-dimensional halogen-bonded network to be reported.

The hydrothermal reaction of uranyl nitrate with 1,4-benzenedicarboxylic acid (Hbdc) in the presence of strontium or potassium hydroxides and nitrates afford the formation of two new uranyl hybrid materials featuring extensive uranyl-strontium or uranyl-potassium interactions with [(UO)(µ-O)(µ-OH)] as the sub-building unit. Sr[(UO)(O)(OH)(bdc)]⋅6HO (1) contains one-dimensional (1D) uranyl oxohydroxyl ribbons made of trinuclear pentagonal bipyramidal uranyl units. The ribbons are linked together via uranyl-strontium interactions to form 2D inorganic domains which are further connected through µ-bdc anions forming a 3D hybrid structure. This is the first reported uranyl-strontium interaction in extended hybrid solid with the shortest Sr-O bond length of 2.596 (8) A. K[(UO)(O)(OH)(bdc)]⋅8HO (2) has a similar 3D hybrid structure built up through extensive K-O interactions with the shortest K-O bond length of 2.620 (6) A. Raman spectroscopy has confirmed the presence of oxo-bridging (U−O−U) vibrations. Thermal stabilities and photoluminescent properties are reported.

Correction for ‘Straightening out halogen bonds’ by Caitlin J. Setter et al., CrystEngComm, 2020, 22, 1687–1690, DOI: 10.1039/D0CE00176G.

The synthesis of the extended dipyridyl ligand 4,4′-(2,5-dimethyl-1,4-phenylene)dipyridine (L) in an improved yield via the palladium catalysed Suzuki coupling of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (1) and 1,4-dibromo-2,5-dimethylbenzene (2) is reported along with its use to form a two-dimensional coordination polymer [Co2L2(OAc)4(H2O)2]n. The coordination polymer consists of one-dimensional chains of octahedral cobalt ions bridged by acetate ligands which are connected to form two dimensional sheets with square lattice (sql) topology via the dipyridyl ligands (L). The structure contains small voids totalling ~6.6% of the unit cell volume. The crystal structures 1, L, L·2H2O, and L·2HNO3 are also reported.

The combination of the dicopper platform [Cu2(L)2(THF)2] (1·2THF), where H2L is 1,1'-(1,3-phenylene)-bis-4,4-dimethylpentane-1,3-dione, and 1,4-bis(4-pyridyl)piperazine (bpp), afforded the first example of a one-dimensional polyrotaxane {[(1)(μ2-bpp)][(1)2(bpp)2]}n whose "string" and "bead" are constructed from the same components. The bead of stoichiometry [(1)2(bpp)2] has a large rectangular cavity of dimensions 7.40 × 15.64 Å and is threaded onto a stair-like string of composition [(1)(μ2-bpp)]n. The formation of the polyrotaxane is driven by π-π stacking between the string and the beads with precise electronic and steric complementarity between these components. A pathway for the formation of the polyrotaxane is proposed.

The supramolecular assemblies formed from lanthanide cations (Ln3+) and a new alkyl-substituted cucurbituril, the ortho-tetramethyl substituted cucurbituril (o-TMeQ[6]), in neutral solution were investigated. X-ray single crystal diffraction analysis revealed that interactions of the aqua complexes of lanthanide cations with o-TMeQ[6] gives rise to an isomorphous group of compounds when heavy lanthanide cations such as Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+ and Lu3+ are employed. Interestingly, no solid crystals were obtained from o-TMeQ[6]–Ln3+ systems of La, Ce, Pr, Nd, Sm, Eu or Gd, suggesting that these interactions could be used for the isolation of heavier lanthanide cations from their lighter counterparts.

Two solvated cobalt(II) terpyridine complexes, [Co(MeO-terpy)2](BF4)2·H2O (1·H2O) and [Co(MeO-terpy)2](BF4)2·acetone (1·acetone) were prepared. Annealing each of these complexes resulted in the formation of two desolvated species, 1 and 1′, respectively. 1·H2O and 1 exhibited two-step and gradual SCO. The compound 1·acetone has high-spin at all temperatures and 1′ undergoes a reverse spin transition due to a phase change.

A large discrete face-capped tetranuclear iron(II) cage, [Fe4L4](BF4)8·n(solvent), was synthesised via metal-ion directed self-assembly. The cage is formed from a rigid tritopic ligand that incorporates chelating imidazole-imine functional groups. The cage displays temperature induced spin-crossover and LIESST effects and is amongst the largest iron(II) tetrahedral cages with such properties reported. The synthesis, structure and magnetic properties of this new metallo-cage are presented.

A series of five coordination compounds, namely, {[Co3(stp)2(bipy)(H2O)4]·2H2O}n, (1), {[Co3(stp)2(bipy)5(H2O)6]·4H2O}n, (2), [Co3(stp)2(bipy)4(H2O)10]·8H2O, (3), [Co(Hstp)2(Hbipy)2], (4) and {[Co(stp)2(H2O)2][Co(bipy)2(H2O)4]}·2Hbipy·2H2O, (5) have been synthesised hydrothermally, through the reaction of different molar ratios of 2-sulfoterephthalic acid monosodium salt, Na(H2stp), cobalt(II) nitrate hexahydrate and the N-donor ancillary co-ligand 4,4′-bipyridine (bipy). Due to the combination of the multiple potential coordination modes of the stp ligand and the bipy co-ligand, the products are structurally and topologically diverse with the connectivities of the materials dependent on the ratios of starting materials employed. Single-crystal X-ray diffraction studies show that compound 1 is a three-dimensional coordination polymer, compound 2 consists of infinite one-dimensional zig-zag chains, compound 3 is a discrete trinuclear complex, compound 4 is a discrete mononuclear complex and compound 5 is an ionic solid consisting of both cobalt containing cations and anions. Magnetic studies show that the Co(II) ions in 1 are strongly coupled, while 2, 3 and 5 show insignificant coupling due to larger metal–metal separations. Modelling required the introduction of zero field splitting parameters due to orbital angular momentum contributions in these cases.

The cobalt derivative {[Co3(2-stp)2(dpp)4]·2H2O}n (1) has been hydro(solvo)thermally synthesised by combining sodium 2-sulfoterephthalic acid (2-stpH2Na) and divalent cobalt nitrate in presence of the flexible N-donor co-ligand dpp (1,3-di(4-pyridyl)propane). Single-crystal X-ray diffraction shows that 1 is a two-dimensional coordination polymer with carboxylate and sulfonate oxygens and pyridyl nitrogens coordinated to the two symmetry independent octahedral cobalt(II) centres. UV-Vis, magnetic and EPR studies show that the cobalt(II) centres are high-spin. Compound 1 proved to be robust to the removal of the solvent water molecules, which was achieved by heating the sample to yield the desolvated complex {[Co3(2-stp)2(dpp)4]}n (2). 2 was also characterised by single-crystal X-ray diffraction at 331 K. Gas sorption studies on this material showed only surface binding of N2 and modest uptake for CO2. The crystallographic analysis also shows that upon desolvation, the flexible propyl groups of the dpp ligand adjust their positions, reducing the potentially accessible void volumes and accounting for the gas adsorption results.

The synthesis, molecular structure as well as in situ spectroelectrochemical and electron spin resonance (ESR) studies of 5,7,8,10,15,17,18,20-octaphenyl-21,23-dithiaporphyrin (S2OPP) are presented. The compound investigated can be reversibly oxidised and reduced to yield the corresponding stable monocation and monoanion species, respectively. The experimental ESR spectrum of S2OPP•+ can be simulated taking into account the splitting constants 2xa N = 2.3 G from two dominating equivalent nitrogen nuclei. The computed spin delocalization at the density functional theory (DFT) for the cation is completely different compared to the spin delocalization of the corresponding monoanion. The largely delocalized unpaired spin density over the heteroatoms of dithiaporphyrin macrocycle was confirmed for the S2OPP•– radical anion. The role of the phenyl substitution in the meso- or β-positions of the parent 21,23-dithiaporphyrin S2P was also investigated theoretically and the results are compared with the normal (N4 core) porphyrin molecule.

Different anionic templates act to give rise to four distinct Cd(II)-based architectures: a Cd2L3 helicate, a Cd8L12 distorted cuboid, a Cd10L15 pentagonal prism, and a Cd12L18 hexagonal prism, which respond to both anionic and cationic components. Interconversions between architectures are driven by the addition of anions that bind more strongly within a given product framework. The addition of Fe(II) prompted metal exchange and transformation to a Fe4L6 tetrahedron or a Fe10L15 pentagonal prism, depending on the anionic templates present. The equilibrium between the Cd12L18 prism and the Cd2L3 triple helicate displayed concentration dependence, with higher concentrations favoring the prism. The Cd12L18 structure serves as an intermediate en route to a hexafluoroarsenate-templated Cd10L15 complex, whereby the structural features of the hexagonal prism preorganize the system to form the structurally related pentagonal prism. In addition to the interconversion pathways investigated, we also report the single-crystal X-ray structure of bifluoride encapsulated within a Cd10L15 complex and report solution state data for J-coupling through a CH···F(-) hydrogen bond indicating the strength of these interactions in solution.

The di-topic terpy/dpa hybrid ligand, 4′-{4-[bis(2-pyridyl)aminomethyl]phenyl}-2,2′:6′,2′′-terpyridine (L), incorporating both 2,2′:6′,2′′-terpyridine (terpy) and 2,2′-dipyridylamino domains has been synthesised. The metal complexes [CoLCl2], [ZnLCl2], [ZnL(CH3CO2)2], [Fe(L)2(PF6)2] and [Fe(L)(HL)](PF6)0.5(ClO4)2.5 have been isolated. X-ray structures of all five structures show that the respective metal ions preferentially bind to the terpy site of L, with the dpa site in the first four complexes remaining empty. In the fifth complex, which was isolated following the attempted reaction of silver perchlorate with [Fe(L)2(PF6)2], one dpa site is protonated. The crystal packing of all these species is dominated by extensive π-interactions. The 5-coordinate zinc(II) and cobalt(II) complexes are isostructural and exhibit a 3D network of interactions involving π-stacking as well as CH⋯Cl and CH⋯N hydrogen bonding. Similar interactions occur in the packing of [ZnL(CH3CO2)2] and [Fe(L)(HL)](PF6)0.5(ClO4)2.5 giving rise to 3D arrays. Reaction of palladium(II) with L yields a product of stoichiometry Pd2LCl4 for which the evidence suggests that palladium binds at both the terpy and dpa domains. Based on this result, addition of [Pd(CH3CN)2Cl2] to [Fe(L)2](PF6) in acetonitrile yielded a heterometallic complex in which the “free” dpa sites of [Fe(L)2](PF6) are now occupied by palladium ions to form a heterometallic product of type [FePd2(L)2Cl4](PF6)2·1.5CH3CN.

Complex cubes: In a cationic supramolecular cube, coordinatively unsaturated metal centers in the walls of the host provided binding sites for neutral or negatively charged guests. The binding of an initial guest (CF CO, OPMe, NH, or NMe) either cooperatively enhanced or competitively inhibited the binding of a second guest (halide ion).

A rigid organic ligand, formed through the subcomponent self-assembly of p-toluidine and 6,6'-diformyl-3,3'-bipyridine, was employed in a systematic investigation into the synergistic and competing effects of metal and anion templation. A range of discrete and polymeric metal-organic complexes were formed, many of which represent structure types that have not previously been observed and whose formation would not be predicted on taking into account solely geometric considerations. These complex structures, capable of binding multiple guests within individual binding pockets, were characterized by NMR, ESI-MS, and single-crystal X-ray diffraction. The factors that stabilize individual complexes and lead to the formation of one over another are discussed.

Cubes: The rational design of a simple set of organic subcomponents led to the formation of a ML cubic capsule upon their self-assembly with Fe ions. By altering the length of alkyl chains on these subcomponents, the solubility of the assembled structures was greatly increased in apolar solvents, such as cyclohexane, and the structures displayed solvent-dependent host-guest interactions.

A tridentate hydrazone precursor, N′-[1-(pyridin-2-yl)ethylidene]acetohydrazide (L) (1:1 refluxed product of acetichydrazide and 2-acetylpyridine), produced two octahedral CuII and NiII derivatives, [CuL2]·NO3 (1) and [NiL2]·ClO4·H2O (2). Both are subjected to X-ray diffraction system, and structural investigation shows that the central metal atom (CuII or NiII) adopts a distorted octahedral geometry with N4O2 donor sets by coordination of a pair of independent hydrazone precursors. Besides X-ray study, IR and UV-vis spectra, thermal analysis and room temperature magnetic moments are utilized for establishing significant characteristics of both complexes. It is apparent that the M-Npyridine bonds are slightly longer than the M-Nimino bonds, Cu1-N1 and Cu1-N4 [2.300(2) and 2.038(2) Å] for 1 and Ni1-N1 and Ni1-N4 [2.075(2) and 2.084(1) Å] for 2, Cu1-N2 and Cu1-N5 [2.062(1) and 1.932(1) Å] for 1 and Ni1-N2 and Ni1-N5 [2.008(2) and 1.975(2) Å] for 2, respectively. As per our observation, the effective magnetic moment value (µeff) is found to be 1.77 B.M. for 1 and 3.06 BM for 2, respectively.

Metallosupramolecular polyhedra are inherently beautiful. As metallosupramolecular chemistry developed, it quickly became apparent that designed modifications could be used to vary the size, shape and symmetry of polyhedral architectures. Metallosupramolecular polyhedra, by their very nature, usually contain space within them. This chapter elaborates on these factors, describing the key steps in the evolution of the chemistry of chiral metallosupramolecular polyhedra and the current applications for these remarkable complexes. It examines how the creation of a chiral cavity within polyhedra makes them selective for chiral guests and how it makes them useful for enantiomeric separations, or perhaps applications as chiral catalysts. The chapter defines positive stereochemical coupling to be the deviation of the proportion of diastereomers present towards chiral diastereomers from the statistical ideal and negative stereochemical coupling to be the deviation of the proportion of diastereomers present towards the achiral (meso) forms.

CdII transformer: By using a linear dialdehyde, CdII ions, and different amines, different architectures were constructed, including an M2L3 4+ triple helicate, an M 3L3 6+ triangle, an M4L8+ cryptate, as well as an M12L18 24+ hexagonal prism. These structures could be interconverted in a complex network by dynamic imine exchange, the addition of a template, or a change in the pH value of the solution.