Secondary Non-covalent Interactions Research Articles

Supramolecular Viologen–Cyclodextrin Electrolytes for Aqueous Organic Redox Flow Batteries

Along with a primary modification of redox active materials, an additional introduction of secondary noncovalent interactions can synergistically enhance bulk properties of electrolytes for redox flow batteries. Herein, we highlight the host–guest complex formation between tailored viologens and highly water soluble (2-hydroxypropyl)-β-cyclodextrin as a key electrolyte interaction to modulate relevant electrochemical properties of aqueous redox flow batteries (AORFBs). The cyclodextrin-modified AORFB anolytes demonstrated a complex interrelation of molecular structure and inherent binding activity as well as bulk electrochemical stability of the anolyte. The screening of different combinations of viologen substituents in the presence of cyclodextrin enabled an electrochemically stable AORFB performance for more than 500 cycles with a temporary capacity fade rate of 0.26%/day at high energy (>70%) and Coulombic (>99.7%) efficiencies. A selective interplay of supporting electrolytes and engineered redox active materials is a promising strategy for enhanced energy characteristics of AORFB electrolytes.

Coordination compound containing σ-hole interactions: Synthesis and crystal structure of NH4[Cr(CO(NH2)2)6][Hg(SCN)4]2·2H2O

The crystallographic analysis of complex, NH4[Cr(CO(NH2)2)6][Hg(SCN)4]2⋅2H2O (1) has revealed that its cations and anions are held together by secondary non-covalent interactions. These interactions have led to the formation of four σ-holes, one on Hg and three on S atoms. The molecular electrostatic potential (MEP) study confirms that the σ- holes on sulphur are large enough to generate interactions between S...S (chalcogens) and S...N (chalcogen-pincogen) in [Hg(SCN)4]2−. Single crystal X-ray diffraction of 1 has revealed that [Cr(CO(NH2)2)6]3+ are stacked one upon another running parallel along a-axis and surrounded by a “cylinder” consisting of anions, ammonium cations and water molecules. The supramolecular architecture has been obtained which is being stabilized by intermolecular hydrogen bonding interactions (O-H⋅⋅⋅N, O-H⋅⋅⋅S, N-H⋅⋅⋅N, N-H⋅⋅⋅O (H2O)) along with the formations of σ-hole interactions. The crystals of 1 has been obtained using one-pot synthetic method by reacting [Cr(CO(NH2)2)6]Cl3⋅3H2O, HgCl2 and NH4SCN (in 1:2:8 molar ratio) in aqueous medium and have been initially characterized by UV-visible and IR spectroscopy.

Ferrocene-functionalized anilines as potent anticancer and antidiabetic agents: Synthesis, spectroscopic elucidation, and DFT calculations

Ferrocene derivatives have attracted significant interest as potent biological agents and novel drug candidates. Hence, the present research work was focused on the synthesis and characterization of ferrocene-integrated anilines (FB1-FB4) through different spectroscopic techniques such as: FT-IR, multinuclear (1H and 13C) NMR, Raman, atomic absorption spectroscopy, elemental analysis, and single-crystal X-ray crystallography. The crystallographic analysis revealed a supramolecular structure mediated by secondary non-covalent interactions (π—H and π—π). These ferrocenyl derivatives demonstrated a quasi-reversible electrochemical behavior with one electron transfer from Fe(II) to Fe(III)., which was evident by the change in the peak potential at different scan rates. The theoretically calculated energies of the HOMO-LUMO orbitals and the Mulliken charge distribution for the optimized structures determined by the DFT/B3LYP method associated well with the electrochemically measured redox potentials. The computational measurements also led to a close agreement between the found and observed vibrational frequencies having a correlation coefficient of 0.999. The in silico docking analysis against α-amylase, urease, and tyrosine kinase revealed that the docking scores are in close agreement with the in vitro obtained IC50 values of inhibitors. The synthesized compounds exhibited notable free radical scavenging activity against DPPH with IC50 values between 15.9–31.5 µM. The anticancer activity data revealed modest cytotoxicity against the subjected cancer cell line (MCF-7) compared with standard chemotherapeutic drug (cisplatin). However, these ferrocenyl analogs had fewer toxic effects in normal cells (MCF-10A). The results of the antidiabetic assay established that FB1 (IC50 = 19.27 µg/mL) is potentially more active inhibitor of α-amylase, the theoretical docking studies stating that FB1 is more prone towards hydrophobic interactions with Leu165 and Trp 59, in the active pocket of alpha-amylase. Together, the current study reveals the anti-cancer, anti-diabetic and anti-oxidant potential of newly synthesized ferrocene-substituted anilines.

Non-covalent interactions involving remote substituents influence the topologies of supramolecular chains featuring hydroxyl-O–H⋯O(hydroxyl) hydrogen bonding in crystals of (HOCH2CH2)2NC(S)N(H)(C6H4Y-4) for Y = H, Me, Cl and NO2

Secondary non-covalent interactions prove crucial in determining the topology of supramolecular chains sustained by conventional O–H⋯O hydrogen bonding.

Acidity-Driven Bidirectional Room-Temperature Spin-State Switch and Fluorescence Modulation of a Mononuclear Fe(II) Complex

Room-temperature switchable materials showing multiple responses toward external stimuli are highly desired. Herein, we report bidirectional spin-state switch and fluorescence modulation of an Fe(I...

2-Amino-3-methylpyridinium, 2-amino-4-methylbenzothiazolium and 2-amino-5-chloropyridinium salts. Experimental and theoretical findings

Reaction between 2-amino-3-methylpyridine, 2-amino-4-methylbenzothiazole with salicylic acid, and 2-amino-5-chloropyridine with 3-chlorobenzoic acid were carried out and respective molecular salts 1–3 were obtained. During reactions, proton transfer from acid to endocyclic N of the base was observed. Structural elucidation of all compounds was carried out with the help of FT-IR and X-ray Diffraction for single crystals. The acid/base pairs in a molecular salt are held together with the help of H- and charge-assisted bonding and additional non-covalent bonding extend the supramolecular structure. All hydrogen bonds and secondary interactions have been discussed and a detailed comparison of experimental data with theoretical calculations through AIM, NBO and Wiberg bond index analysis has been made. The non-covalent character was mainly typified by positive values of Laplacian of electronic density. The theoretical studies demonstrate that other than classical H-bonds, the non-classical and secondary non-covalent interactions are very important to direct supramolecular structure of the respective molecular salt. The DFT calculations with solvent model SMD proved a good alternative to deduce the molecular salt formation when the 0>ΔpKa>3. Moreover, global reactivity descriptors (GRD) have been calculated utilizing the energies of FMOs. The calculated values for HOMO of compounds 1–3, -5.469, -5.642 and -6.435, respectively indicate that the compounds adopt the numerical order in terms of electron donation/Lewis basicity. The molecular salt formation is more feasible for heterosynthon 1 and least for 3.

Rationalization of Lattice Thermal Expansion for Beta-Blocker Organic Crystals

Anisotropic lattice expansion could be a source of misunderstanding in powder pattern recognitions, especially in the case of organic crystals where for the interpretation of room temperature patterns single crystal data at low temperature are usually used. Trying to rationalize the thermal lattice expansion, we studied two close related β-blocker molecules with similar packing in the solid state but with different thermal behavior. Solid state calculations, using the fast and accurate HF-3c method and the quasi harmonic approximation for the simulation of the lattice expansion, were able to reproduce the experimental trends with good accuracy. The complete analysis of the calculated thermal expansion of the two structures, as well as of other structures with similar packing found in a database survey, revealed the primary role of the hydrogen bonds. Secondary non-covalent interactions in the plane perpendicular to the hydrogen bond system could also play a role.

Influence of anion variation and cation modification on the packing of tetraazamacrocyclic Au(III) complexes

Abstract The work presents the analysis of the packings of crystal structures of unsaturated tetraazamacrocyclic gold(III) complexes with different anions ([Au(С14H22N4)]X (X = Br (I), ReO4 (II), BPh4 (III), AuBr2 (IV)) and with modified (halogenated [Au(С14Н20N4Y2)]ClO4 (Y = Cl (V), Br (VI), protonated [Au(С14H23N4)](ClO4)2 (VII), [Au(С14H24N4)](H3O)(ClO4)4 (VIII) cations. Crystal-chemical regularities and features of the packings depend on the composition and structure of cations, as well as on the nature and geometry of counter-anions. In the packings of the complexes I–VII whose ligands contain one or two iminate six-membered rings, the 3D supramolecular architecture of the crystal lattice is determined and stabilized by an extensive network of secondary non-covalent intermolecular interactions (non-classical H-bonds C–H…A (A = π, Br, Cl, O, Au) and contacts Au⋯Au (O, N, π); O⋯Cl (Br, N). In the iminate complexes with nonlinear inorganic anions Br−, ClO4−, ReO4−, the main structure-forming role belongs to the cations which are interconnected by non-classical H-bonds C–H…π. The halogenation of iminate rings of the cation and the protonation of one of the rings do not cause profound changes in the packing. In the structures of the complexes with a bulky organic anion BPh4– (III) and with a coordinatively unsaturated linear anion AuBr2− (IV), the decisive role belongs to the anions which prevent the association of cations by forming H-bonds and contacts with them. The linear acceptor-active anion AuBr2− has the greatest influence on the packing of diiminate macrocyclic gold(III) complexes by providing the parquet packing of the structure. The 1D crystal structure of the diprotonated diimine complex VIII is stabilized by classical H-bonds Ow–H...O of the oxonium ion and by the contacts of the central atom of the macrocyclic cation Au⋯O.

Ternary Complexes Stabilized by Chalcogen and Alkaline-Earth Bonds: Crucial Role of Cooperativity and Secondary Noncovalent Interactions.

High-level G4 calculations show that the strength of chalcogen interactions is enhanced dramatically if chalcogen compounds simultaneously form alkaline-earth bonds. This phenomenon is studied by exploring binary YX2 ⋅⋅⋅N-Base complexes and two types of ternary MCl2 ⋅⋅⋅YX2 ⋅⋅⋅N-Base, YX2 ⋅⋅⋅N-Base⋅⋅⋅MCl2 complexes, in which YX2 is a chalcogen compound (Y=S, Se; X=F, Cl), the N-Bases are sp, sp2 , and sp3 bases (NCH, HN=CH2 , NH3 ), and MCl2 are alkaline-earth BeCl2 or MgCl2 derivatives. Starting from the chalcogen-bonded complexes YX2 ⋅⋅⋅NH3 and YX2 ⋅⋅⋅HN=CH2 , the binding site of a new incoming alkaline-earth bond is found, surprisingly, to depend on the nature of the halogen atom attached to the chalcogen. For the YF2 binary complexes the association site is the F atom of the YF2 subunit, whereas for YCl2 it is the N atom of the nitrogen base. Regarding YX2 ⋅⋅⋅NCH complexes, N is the most favorable site for an alkaline-earth interaction in ternary complexes, regardless of which YX2 derivative is used. The explanation relies on the interplay of all the noncovalent interactions involved: the strong cooperativity between chalcogen and alkaline-earth bonds, and the appearance of secondary noncovalent interactions in the form of hydrogen bonds.

Directing Foldamer Self-Assembly with a Cyclopropanoyl Cap.

The rational design of self-assembling organic materials is extremely challenging due to the difficulty in precisely predicting solid-state architectures from first principles, especially if synthons are conformationally flexible. A tractable model system to study self-assembly was constructed by appending cyclopropanoyl caps to the N termini of helical α/β-peptide foldamers, designed to form both N-H⋅⋅⋅O and Cα -H⋅⋅⋅O hydrogen bonds, which then rapidly self-assembled to form foldectures (foldamer architectures). Through a combined analytical and computational investigation, cyclopropanoyl capping was observed to markedly enhance self-assembly in recalcitrant substrates and direct the formation of a single intermolecular N-H⋅⋅⋅O/Cα -H⋅⋅⋅O bonding motif in single crystals, regardless of peptide sequence or foldamer conformation. In contrast to previous studies, foldamer constituents of single crystals and foldectures assumed different secondary structures and different molecular packing modes, despite a conserved N-H⋅⋅⋅O/Cα -H⋅⋅⋅O bonding motif. DFT calculations validated the experimental results by showing that the N-H⋅⋅⋅O/Cα -H⋅⋅⋅O interaction created by the cap was sufficiently attractive to influence self-assembly. This versatile strategy to harness secondary noncovalent interactions in the rational design of self-assembling organic materials will allow for the exploration of new substrates and speed up the development of novel applications within this increasingly important class of materials.

Synthesis and computational study of new meta- and para-substituted ferrocenyl thioureas as potent protein kinase inhibitors and cytotoxic agents

The present study describes the synthesis, characterization, DNA binding and in vitro biological evaluation of ferrocene-enhanced thioureas. The new complexes (N1–N6) were prepared by reacting ferrocenyl anilines (A-B) with freshly prepared isothiocyanates in dry acetone. A crystallographic study of N3 revealed a supramolecular structure involving secondary non-covalent interactions (π⋯H and π⋯π). The nature and extent of the binding of these complexes with the salmon sperm DNA (SS-DNA) were examined by cyclic voltammetry and UV–Vis spectroscopy. The complexes have strong binding to DNA with binding constants ranging from 9.83 × 103 to 5.76 × 104 M−1. The shifts in the cathodic peak potentials with the addition of DNA in the electrochemical studies of the new complexes are attributed to electrostatic interactions. This observation is an indicator of the oxidizable behavior of the complexes in the presence of DNA. The theoretically calculated energies of the frontier molecular orbitals (EHOMO and ELUMO) and the Mulliken charge distributions for the optimized structures determined by the DFT/B3LYP method correlate well with the electrochemically determined redox potentials (correlation coefficient, 0.986). The computational measurements also led to a close agreement between the calculated and observed vibrational frequencies. The new complexes proved to be good candidates for protein kinase inhibition and cytotoxicity studies.

Dynamic Hydrogels from Host-Guest Supramolecular Interactions.

Hydrogel biomaterials are pervasive in biomedical use. Applications of these soft materials range from contact lenses to drug depots to scaffolds for transplanted cells. A subset of hydrogels is prepared from physical cross-linking mediated by host-guest interactions. Host macrocycles, the most recognizable supramolecular motif, facilitate complex formation with an array of guests by inclusion in their portal. Commonly, an appended macrocycle forms a complex with appended guests on another polymer chain. The formation of poly(pseudo)rotaxanes is also demonstrated, wherein macrocycles are threaded by a polymer chain to give rise to physical cross-linking by secondary non-covalent interactions or polymer jamming. Host-guest supramolecular hydrogels lend themselves to a variety of applications resulting from their dynamic properties that arise from non-covalent supramolecular interactions, as well as engineered responsiveness to external stimuli. These are thus an exciting new class of materials.

Informing Molecular Design by Stereoelectronic Theory: The Fluorine Gauche Effect in Catalysis.

The axioms of stereoelectronic theory constitute an atlas to navigate the contours of molecular space. All too rarely lauded, the advent and development of stereoelectronic theory has been one of organic chemistry's greatest triumphs. Inevitably, however, in the absence of a comprehensive treatise, many of the field's pioneers do not receive the veneration that they merit. Rather their legacies are the stereoelectronic pillars that persist in teaching and research. This ubiquity continues to afford practitioners of organic chemistry with an abundance of opportunities for creative endeavor in reaction design, in conceiving novel activation modes, in preorganizing intermediates, or in stabilizing productive transition states and products. Antipodal to steric governance, which mitigates destabilizing nonbonding interactions, stereoelectronic control allows well-defined, often complementary, conformations to be populated. Indeed, the prevalence of stabilizing hyperconjugative interactions in biosynthetic processes renders this approach to molecular preorganization decidedly biomimetic and, by extension, expansive. In this Account, the evolution and application of a simple donor-acceptor model based on the fluorine gauche effect is delineated. Founded on reinforcing hyperconjugative interactions involving C(sp3)-H bonding orbitals and C(sp3)-X antibonding orbitals [σC-H → σC-X*], this general stratagem has been used in conjunction with an array of secondary noncovalent interactions to achieve acyclic conformational control (ACC) in structures of interest. These secondary effects range from 1,3-allylic strain (A1,3) through to electrostatic charge-dipole and cation-π interactions. Synergy between these interactions ensures that rotation about strategic C(sp3)-C(sp3) bonds is subject to the stereoelectronic requirement for antiperiplanarity (180°). Logically, in a generic [X-CH2-CH2-Y] system (X, Y = electron withdrawing groups) conformations in which the two C(sp3)-X bonds are synclinal (i.e., gauche) are significantly populated. As such, simple donor-acceptor models are didactically and predictively powerful in achieving topological preorganization. In the case of the gauche effect, the low steric demand of fluorine ensures that the remaining substituents at the C(sp3) hybridized center are placed in a predictable area of molecular space: An exit vector analogy is thus appropriate. Furthermore, the intrinsic chemical stability of the C-F bond is advantageous, thus it may be considered as an inert conformational steering group: This juxtaposition of size and electronegativity renders fluorinated organic molecules unique among the organo-halogen series. Cognizant that the replacement of one fluorine atom in the difluoroethylene motif by another electron withdrawing group preserves the gauche conformation, it was reasoned that β-fluoroamines would be intriguing candidates for investigation. The burgeoning field of Lewis base catalysis, particularly via iminium ion activation, provided a timely platform from which to explore a postulated fluorine-iminium ion gauche effect. Necessarily, activation of this stereoelectronic effect requires a process of intramolecularization to generate the electron deficient neighboring group: Examples include protonation, condensation to generate iminium salts, or acylation. This process, akin to substrate binding, has obvious parallels with enzymatic catalysis, since it perturbs the conformational dynamics of the system [ synclinal-endo, antiperiplanar, synclinal-exo]. This Account details the development of conformationally predictable small molecules based on the [X-Cα-Cβ-F] motif through a logical process of molecular design and illustrates their synthetic value in enantioselective catalysis.

Synthesis, structural characterization, in vitro bioactivities, interaction with SS-DNA and DFT study of 4-chloro-3-ferrocenylaniline

We report here the synthesis, characterization (FT-IR, multinuclear (1H and 13C) NMR, Raman, AAS, elemental analysis and single-crystal XRD), DNA binding (cyclic voltammetry, UV–Vis spectroscopy and viscometry) and in vitro biological screening of 4-chloro-3-ferrocenylaniline (CFA). The crystallographic analysis revealed a supramolecular structure mediated by secondary non-covalent interactions (π⋯H and π⋯π). The DNA binding studies performed by cyclic voltammetry and UV–Vis spectroscopy produced results that are in close agreement with one another for the binding constants (K), 1.64×104M−1 and 2.39×104M−1, respectively, and an electrostatic mode of interaction was observed. The diffusion coefficient of the drug-DNA adduct (1.02×10−6cm2s−1) is lower than that for the free drug (1.31×10−6cm2s−1) indicating slow diffusion of the comparatively high molecular weight drug towards the electrode in the cyclic voltammetric study. The binding site size of 0.309 base pairs is also consistent with electrostatic interactions. The nature and the extent of interaction with DNA was also investigated by viscometry. DFT/B3LYP method was used to determine the charge distribution and HOMO/LUMO energies of the optimized structure. The CFA compound exhibited good free radical scavenging activity against DPPH with an IC50 value of 160μM. CFA was also screened for antimicrobial, cytotoxic and protein kinase inhibition potential and proved to be good candidate in terms of microbial growth and protein kinase inhibition. These properties may prove valuable in the future design of new anticancer and antimicrobial drugs.

New supramolecular ferrocene incorporated N,N′-disubstituted thioureas: synthesis, characterization, DNA binding, and antioxidant studies

Ferrocene incorporated N,N′-disubstituted thioureas (S1–S6) were synthesized by allowing 4-ferrocenyl-3-methylaniline to react with freshly prepared aliphatic isothiocyanates and were characterized by using different analytical techniques. Based on single-crystal X-ray analysis compound S1 shows supramolecular structure mediated by secondary bonding interactions, intermolecular hydrogen bonding NH–O, NH–S, and secondary non-covalent interactions (π–H). Voltammetric measurements were used to study their redox behavior and DNA binding of the compounds. Different binding parameters like binding constants, binding energies, and diffusion coefficients (Do) were calculated for further insight on the affinity with DNA. All the compounds show electrostatic mode of interactions. The Do of molecule-DNA adducts were found to be lower than that of free molecule. Compounds S1–S6 having 50% inhibition values less than 37.89 μg mL−1 indicate that they may have value as antioxidants to be used as therapeutic agents.

Supramolecular H-bonded porous networks at surfaces: exploiting primary and secondary interactions in a bi-component melamine–xanthine system

The control over the formation of a bi-component porous network was attained by the self-assembly at a solid-liquid interface by exploiting both primary and secondary non-covalent interactions between melamine and N(3)-alkylated xanthine modules.

Study of New Ferrocene Incorporated N,N′-Disubstituted Thioureas as Potential Antitumour Agents

In this paper, we report the synthesis, structural characterisation, cytotoxicity against human ovarian tumour models (A2780, A2780cisR, and A2780ZD0473R), nature of interaction with calf-thymus (CT)-DNA and pBR322 plasmid DNA of new ferrocene based N,N′-disubstituted thioureas (3a–d). The compounds, characterized based on elemental analysis, FT-IR and multinuclear (1H and 13C) NMR spectroscopy, and single crystal X-ray diffractometry, were found to have significant antitumour activity although much less than cisplatin. Crystallographic data reveals the existance of secondary interactions for compound 3c in terms of intermolecular hydrogen bonding of type NH⋯O, NH⋯S and secondary non-covalent interactions (π⋯H). When pBR322 plasmid DNA was interacted with increasing concentrations of compounds, 3a and 3b but not 3c were found to partially prevent BamH1 digestion of the DNA. The negative shift in peak potential in voltammetric measurements indicates that all the compounds undergo electrostatic interactions with the negatively charged phosphate DNA backbone. The large negative value of the binding energy indicates the spontaneity of reaction between the compounds and CT-DNA and the conformational stability of adducts formed.

Synthesis and Structure of Palladium 1,2,3-Triazol-5-ylidene Mesoionic Carbene PEPPSI Complexes and Their Catalytic Applications in the Mizoroki–Heck Reaction

New mono- and bimetallic 1,2,3-triazol-5-ylidene mesoionic carbene (MIC) complexes of Pd have been synthesized, isolated, and characterized. We have described the synthesis of a bis(MIC) complex via transmetalation from a Ag-MIC complex and two PEPPSI-type complexes which are directly available from their respective triazolium salts by treatment with PdCl2 in pyridine. The X-ray structures are reported for all complexes described herein. Interestingly, each complex described exhibits various secondary noncovalent interactions in the solid state of the general type C–H···Cl, which appear to be important for the stabilization of the solid-state structure of the complexes. We further demonstrated the utility of the new PEPPSI complexes in the Mizoroki–Heck reaction. In the case of aryl iodides and electron-deficient bromides, high conversion is observed with methyl acrylate. Hg poisoning tests suggest that, even with an easily dissociated ligand, the reaction likely proceeds via Pd nanoparticles.

New supramolecular ferrocenyl amides: synthesis, characterization, and preliminary DNA-binding studies

Three ferrocenyl amides have been synthesized and characterized by analytical techniques. Based on single-crystal X-ray analysis, a supramolecular structure was attributed to 1 owing to the presence of intermolecular non-covalent interactions. UV-Visible spectroscopy, viscometry, and dynamic laser light scattering was used to assess the mode of interaction and binding of these complexes with DNA, which varied in the sequence 1 > 2 > 3. The binding is presumably due to the ability of these complexes to form secondary non-covalent interactions with DNA bases. Complex-DNA adduct formation depends on the nature of R of the amide.

CoxCu1−x(DDOP)(OH2)(NO3)](NO3): hydrogen bond-driven distortion of cobalt(ii) by solid solution ‘network mismatch’

Late-first row transition metal nitrate complexes of the tetradentate N-donor ligand cis-3,5-bis[(2-pyridinyleneamino]-trans-hydroxycyclohexane (DDOP) adopt a mono-cationic [M(DDOP)(H(2)O)(NO(3))](+) structure (M = Co, 1; Cu, 2; Zn, 3) in which the DDOP ligand occupies the equatorial plane. The complexes are essentially isostructural and isomorphous, allowing the Co(II) and Cu(II) complexes to co-crystallize in mixed-metal solid solutions with the formula [Co(x)Cu(1-x)(DDOP)(NO(3))(H(2)O)](NO(3)), where x = 0.4 (4), 0.1 (5), and 0.7 (6). For 4, structural and magnetochemical analysis indicate that the geometry of the octahedral Co(II) complex distorts to match that of the dominant Jahn-Teller distorted Cu(II) center. Magnetic susceptibility data of octahedral Co(II) are sensitive to ligand geometry distortions and have been analyzed accordingly, comparing 4 to the reference systems 1 and 2. Bond valence calculations have been used to estimate the relative stabilities of the six hydrogen bonded networks, suggesting that the stretching of the Co(II) coordination sphere 4 in is assisted by adoption of the most stable hydrogen bonded network; but that in 6 this is overcome by a higher loading of Co. This family of complexes therefore represent predictable metal-based tectons which can help probe the influence of secondary non-covalent interactions over metal coordination geometries and properties.