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Direct mixing (de novo) and Solvent Assisted Ligand Exchange (SALE) are the main methods used for the synthesis of Mixed-Linker Zeolitic Imidazolate Frameworks (ML-ZIFs). ML-ZIFs with combined –NO2 and –Br/–Cl functionalities were prepared via both synthetic routes. Thereafter the CO2 uptake of the ML-ZIFs were compared, as well as their abilities to fixate CO2 with epoxide substrates. The de novo synthesis resulted in ML-ZIFs with SOD topologies, 60: 40 (–NO2: –Br/–Cl) functionality ratios, higher porosities, better thermal stability and higher CO2 uptake than equivalent SALE products. SALE resulted in smaller ML-ZIF crystallites, only ~ 10% incorporation of –Br/–Cl functionalized imidazolate linkers, and phase change during activation. ML-ZIF-7Cl, obtained from direct mixing, resulted in the highest CO2 uptake (90 cm3 g−1), in line with its higher porosity. ML-ZIF-7Cl, in combination with tetrabutylammonium bromide (TBAB), showed a high catalytic activity (TOF of 446 h−1) for the fixation of CO2 with propylene oxide and was reusable for up to 4 cycles without loss in activity. Graphical Abstract

Two indium(III) complexes, mer-[In(Ox)3]·2H2O (1) and [In2(Ox)2Cl2-μ-[κ2-O,O′-(Ox)2]]·C7H8 (2) (Ox = 8-hydroxyquinolinate), were synthesized and characterised by multi-nuclear NMR in the solid and liquid states. The solid state 1H-NMR spectra of both complexes confirmed the purity of the samples, but in solution it was found that 1 converted to the fac-isomer. The crystal structures of both complexes were determined by single crystal X-ray diffraction. As expected, the In–O bond distance for the bridging oxygen atom is the longest, 2.193 (13) A. Solid state photoluminescence studies revealed that 1 and 2 showed emission at 530 nm and 500 nm, respectively, after excitation at 350 nm. Their respective quantum efficiencies were 13% and 20%. Lifetime measurements were conducted and the dimer showed a double exponential decay with two decay components recording 7.7 ns (30%) and 19.5 ns (70%), whereas the monomer recorded a mono-exponencial lifetime decay of 17.5 ns.

A novel proof-of-concept is reported to modify the water solubility and potential biological effects of a bis(diphenylphosphino)alkylamine (PNP) ligand and the corresponding metal complex, by introducing an amine group on the outer periphery of the pendant ligand arm. Thus, a tertiary butoxycarbonyl protected N’-Boc-ethylenediamine-N,N-bis(diphenylphosphino) (N‘-Boc-PNP) ligand (1) was synthesized by reacting the protected ethylenediamine and chlorodiphenylphosphine in a 1 : 2 molar ratio. The corresponding fac-[Re(CO)3(N‘-Boc-PNP)Br] (1A) complex was then obtained by reacting N‘-Boc-PNP (1) with (Et4N)2fac-[Re(CO)3Br3] in equimolar amounts in DCM at 50 °C. De-protection of the N‘-Boc pendant amine group in 1A with TFA leads to fac-[Re(NH3+-PNP)(CO)3Br]·CF3COO− (1B) which is soluble in D2O (>0.05 M). Treating 1B with saturated aqueous NaHCO3 yields fac-[Re(NH2-PNP)(CO)3Br]·MeOH (1C) in near quantitative yield. Although both 1A and 1C are not soluble in D2O, addition of TFA easily generates 1B (31P NMR), confirming the formation of the protonated amine. Isolation of fac-[99Tc(CO)3(N-Boc-PNP)(Cl)] (1D) confirmed that the rhenium and technetium (99Tc) can be easily interchanged in this process. Reported are hence the unique rhenium series of compounds 1A, 1B and 1C and the corresponding technetium complex 1D, unequivocally characterized by single crystal XRD, as well as IR and 1H NMR spectroscopy. Preliminary antimicrobial evaluation indicates that ligand 1 and its respective rhenium complexes (1A–1C) were not active against selected fungi (Candida albicans and Cryptococcus neoformans) and bacteria (Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Staphylococcus aureus). These types of ligands and complexes therefore present themselves as excellent radio models for further evaluation using 186Re, 188Re and 99mTc to potentially study the radiotoxicity of appropriately designed complexes.

Two bidentate PNP ligands N,N-bis(di-p-tolylphosphino)cyclohexylamine (Cy-pTolPNP) (1) and N,N-bis(di-p-tolylphosphino)cyclobutylamine (Cb-pTolPNP) (2) were synthesized and crystallized. Coordination to the fac-[MI(CO)3]+ core (M = Re, 99Tc) yielded fac-[Re(Cy-pTolPNP)(CO)3Br] (1A), fac-[99Tc(Cy-pTolPNP)(CO)3Cl] (1B), fac-[Re(Cb-pTolPNP)(CO)3Br] (2A) and fac-[99Tc(Cb-pTolPNP)(CO)3Cl] (2B) in relatively good yields (56 to 86 %): The structures of 1, 2, 1A and 1B were studied by single crystal X-ray crystallography. Preliminary mitochondrial/antimicrobial evaluation of the free ligand (N,N-bis(di-p-tolylphosphino)-cyclohexylamine) (1) and its respective fac-[Re(CO)3]+ (1A) complex indicates that neither the free ligand nor the complex was active against selected fungi Eremothecium ashbyii and Nadsonia fulvescens. In addition, all four compounds were found to have no activity against Gram-positive and Gram-negative bacterial species. These biological results are essential to the understanding of how these types of complexes behave and show they are perfectly stable in the evaluated bio-environments. In addition, the results indicate that these ligands and complexes may present themselves as excellent models for radiotoxicity studies using technetium-99m, but more specifically, rhenium Re-186 and Re-188.

A novel proof-of-concept is reported to modify the water solubility and potential biological effects of a bis(diphenylphosphino)alkylamine (PNP) ligand and the corresponding metal complex, by introducing an amine group on the outer periphery of the pendant ligand arm. Thus, a tertiary butoxycarbonyl protected

C13H10O6N3Re, monoclinic, P21/c (no. 14), a = 7.9325(9) Å, b = 13.811(2) Å, c = 13.458(2) Å, β = 92.637(4)°, V = 1472.83(4) Å3, Z = 4, R gt(F) = 0.0249, wR ref(F 2) = 0.0568, T = 100(2) K. CCDC no.: 2024932

C32H48NO2PRh, orthorhombic, P212121 (no. 19), a = 26.784(10) Å, b = 8.837(3) Å, c = 12.759(4) Å, V = 3020.0(18) Å3, Z = 4, R gt(F) = 0.0400, wR ref(F 2) = 0.0920, T = 100(2) K.

C36H39Cl2NOP2Pd, orthorhombic, Pbca (no. 61), a = 19.209(13) Å, b = 15.144(11) Å, c = 24.011(19) Å, V = 6985(9) Å3, Z = 8, R gt(F) = 0.0292, wR ref(F 2) = 0.0867, T = 100 K.

This work entails deep red emitting EuIII based complexes with a variety of ternary β-diketonate ligands and 1,10-phenanthroline as the ancillary ligand in the system. The solid state structure and spectroscopic analysis has been outlaid in terms of photoluminescence and crystallography. A luminescence quantum efficiency of 50% was obtained for the [tris-(4,4,4-trifluoro-1-chlorophenyl-butanedione)mono-(1,10-phenanthroline)europium(III)] complexes. Moreover, complexes [tris-(2,2,6,6-tetramethyl-heptanedione)mono-(1,10-phenanthroline) europium(III)] and {[hexa-(benzyl carboxylic acid) bis-(1,10-phenanthroline)di-europium(III)]-μ-[κ2-O,O′-(benzyl carboxylic acid)]2} were found to also have quantum yields of 9% and 28% with respective sensitization efficiencies of 85%, 15% and 58%. These results were articulated with crystallographic details pertaining to the nature of coordination and the effect of steric and electronic properties thereof which somewhat impacts the Eu–N bond distances. A symmetry correlation was drawn between the crystallographic data and the photoluminescence data.

The synthesis and characterization of two dinuclear complexes, namelyfac-hexacarbonyl-1κ3C,2κ3C-(pyridine-1κN)[μ-2,2′-sulfanediyldi(ethanethiolato)-1κ2S1,S3:2κ3S1,S2,S3]dirhenium(I), [Re2(C4H8S3)(C5H5N)(CO)6], (1), and tetraethylammoniumfac-tris(μ-2-methoxybenzenethiolato-κ2S:S)bis[tricarbonylrhenium(I)], (C8H20N)[Re2(C7H7OS)3(CO)6], (2), together with two mononuclear complexes, namely (2,2′-bithiophene-5-carboxylic acid-κ2S,S′)bromidotricarbonylrhenium(I), (3), and bromidotricarbonyl(methyl benzo[b]thiophene-2-carboxylate-κ2O,S)rhenium(I), (4), are reported. Crystals of (1) and (2) were characterized by X-ray diffraction. The crystal structure of (1) revealed two Re—S—Re bridges. The thioether S atom only bonds to one of the ReImetal centres, while the geometry of the second ReImetal centre is completed by a pyridine ligand. The structure of (2) is characterized by three S-atom bridges and an Re...Re nonbonding distance of 3.4879 (5) Å, which is shorter than the distance found for (1) [3.7996 (6)/3.7963 (6) Å], but still clearly a nonbonding distance. Complex (1) is stabilized by six intermolecular hydrogen-bond interactions and an O...O interaction, while (2) is stabilized by two intermolecular hydrogen-bond interactions and two O...π interactions.

Multinuclear complexes or clusters are rarely investigated in medicinal inorganic chemistry although they represent structural intermediates between molecules and nanomaterials. We present in this report two strategies towards Tc-containing clusters. In a pre-assembly approach, the preformed but incomplete cluster fragment [Re(μ-OH)(μ-OH)(CO)] reacts with [Tc(CO)] to the highly stable [TcRe(μ-OH)(CO)] cube. The same structure self-assembles when reacting the mononuclear Re and Tc precursors in one pot. Integrating the coordinating OH groups from Schiff bases in this concept leads straight to dinuclear, mixed-metal complexes of the type [TcRe(μ-O^N-R)(CO)] in quantitative yields. Both strategies are unprecedented and open a future path towards clusters, incorporating a Tc radiolabel while being decorated with targeting or cytotoxic moieties.

C42H45NO8P2Re2, monoclinic, C2/c (no. 15), a = 24.1612(7) Å, b = 13.0229(3) Å, c = 14.9180(4) Å, β = 121.383(3)°, V = 4007.2(2) Å3, Z = 4, R gt(F) = 0.0235, wR ref(F 2) = 0.0596, T = 173(2) K.

C63H39Cl12Eu2N6O8, triclinic, P1̄ (no. 2), a = 10.720(5) Å, b = 12.232(5) Å, c = 14.267(5) Å, α = 65.288(32)°, β = 71.325(5)°, γ = 88.067(5)°, V = 1599.1(11) Å3, Z = 1, Rgt (F) = 0.0358, wR ref(F 2) = 0.0785, T = 293(2) K.

Five imino salicylidene based bifunctional chelators were developed in order to act as a multipurpose ligand system. The chelators, namely 5-methyl-2-(1,2,4-triazol-3-yliminomethyl)phenol, 2-(9-ethylcarbazol-3-yliminomethyl)-5-methylphenol, 2-[(2-imidazol-4-yl)ethyliminomethyl]-5-methylphenol, 2-[(2-indol-3-yl-ethyl)iminomethyl]-5-methylphenol and 2-[2-(4-hydroxyphenyl)ethyliminomethyl]-5-methylphenol, all of which contain a biological directing functional group on the imine moiety, were investigated via crystallographic and DFT structural studies. Synthesis, in vitro cell testing and photoluminescence are reported indicating specific quantum yields and the respective suitability for radiopharmaceutical development.

The title compound was synthesized using a novel one-pot method under mild conditions and fully characterized using NMR, ESI–MS and SXRD. The supra­molecular structure of the title compound is defined by a combination of C—H⋯N and π–π inter­actions., The preparation of the title compound, C26H25N, was achieved by the condensation of an ethano­lic mixture of benzaldehyde, cyclo­hexa­none and ammonium acetate in a 2:1:1 molar ratio. There are two crystallographically independent mol­ecules in the asymmetric unit. The two cyclo­hexyl rings adopt an anti-envelope conformation with the benzyl moiety adopting a cis conformation with respect to the nitro­gen atom of the phenanthridine segment. In the crystal, mol­ecules are linked through C—H⋯N inter­actions into hydrogen-bonded chains that are further arranged into distinct layers by weak offset π–π inter­actions.

Rhodium(I) carbonyl complexes of the form [RhI(N,O-ScBa)(CO)(PR3)] (R = Ph or Cy), with N,O-ScBaH a mono anionic bidentate Schiff base ligand, 2-(cyclopentyliminomethyl)-5-methylphenol (5-Me-Sal-CyPH), and bearing different phosphine ligands on Rh(I), are reported. N,O-ScBaH was also varied to be 2-(cyclohexyliminomethyl)phenol (Sal-CyH) and 2-(isopropyliminomethyl)-5-methylphenol (5-Me-Sal-IPropH) to investigate the effects of different substituent groups on the periphery of the Schiff bases on metal center reactivity. The structural characterization of two sample complexes is described and an extensive spectroscopic kinetic-mechanistic study utilizing UV/vis, infrared and 31P NMR spectroscopy of the iodomethane oxidative addition is presented. Iodomethane oxidative addition led exclusively to RhIII-alkyl complexes as final products, while an associative activation is inferred from the large negative ΔS ≠ value. The relative reactivity of the [RhI(N,O-ScBa)(CO)(PR3)] complexes when stepwise varying PR3 (PPh3, PPh2Cy, PPhCy2 and PCy3) as tertiary phosphine ligands follow a surprising similar reactivity relationship as observed for a range of isostructural [RhI(X,O-Bid)(CO)(PR3)] complexes, with X = O, N or S in corresponding oxinate, acetylacetonate and thioureate mono anionic X,O-Bid ligands. This suggests systematic and responsive dynamic behavior of the PR3 ligands, independent of the bidentate chelate at the Rh(I) metal center. A variation of more than two orders-of-magnitude in reactivity was observed.

The methanol substitution reactions in the manganese acetylacetonato complex, fac-[Mn(CO)3(acac)(CH3OH)], was kinetically investigated with a range of entering ligands including pyridine (Py), imidazole (Im) and 4-dimethylaminopyridine (DMAP). All the complexes were characterized by NMR, UV–vis and IR spectroscopy. Moreover, crystal structures of fac-[Mn(CO)3(acac)(CH3OH)] (1), fac-[Mn(CO)3(acac)(Py)] (2) and fac-[Mn(CO)3(acac)(DMAP)] (3) are reported. The substitution of methanol in fac-[Mn(CO)3(acac)(CH3OH)] (1) by DMAP is approximately 2 times faster than Py, and 1.7 times faster when compared to Im. The results correlate well with the pKa of the entering nucleophile where pyridine (Py) Δ H ≠ = 73.9 ± 0.6 kJ mol−1 and the entropy of activation Δ S ≠ = −28 ± 2 JK−1 indicating an interchange associative mechanism.

C43H34NO8PS2Re2, monoclinic, P21/c (no. 14), a = 12.165(8) Å, b = 19.027(11) Å, c = 18.848(14) Å, β = 108.735(2)°, V = 4131(5) Å3, Z = 4, R gt (F) = 0.0308, wR ref (F 2 ) = 0.0683, T = 100(2) K.

C19H19N2O4Re, Monoclinic, P21/c (no. 14), a = 8.2805(3) Å, b = 13.7325(5) Å, c = 16.3560(6) Å, β = 92.431(2)°, V = 1858.2(2) Å3, Z = 4, R gt (F) = 0.0347, wR ref (F 2 ) = 0.0930, T = 100 K.

C19H31AgN6O3P2, monoclinic, P21/c (no. 14), a = 16.5661(8) Å, b = 6.1644(3) Å, c = 23.8822(10) Å, β = 114.553(3)°, V = 2218.32(18) Å3, Z = 4, R gt(F) = 0.0188, wR ref(F 2) = 0.0525, T = 100(2) K.

The synthesis and characterization of two dinuclear complexes, namely fac-hexacarbonyl-1κ

C56H58Cl2O4P4Pd2, monoclinic, P21/c (no. 14), a = 12.736(2) Å, b = 18.187(2) Å, c = 12.335(2) Å, β = 109.053(4)°, V = 2700.63 Å3, Z = 2, R gt(F) = 0.034, wR ref(F 2) = 0.0955, T = 100 K.

C34H24Mn2N2O8, triclinic, P1̅ (no. 2) a = 7.737(5) Å, b = 9.483(5) Å, c = 11.309(5) Å, β = 102.514(5)°, V = 766.6(7) Å3, Z = 1, R gt (F) = 0.0478, wR ref (F 2 ) = 0.1297, T = 100(2) K

C20H15N3O·H2O, triclinic, P1̅ (No. 2), a = 7.066(3) Å, b = 9.996(4) Å, c = 12.873(5) Å, α = 86.007(14)°, β = 74.861(14)°, γ = 69.596(13)°, V = 822.4(6) Å3, Z = 2, R gt (F) = 0.0424, wR ref (F 2 ) = 0.1241, T = 100 K.

Multinuclear complexes or clusters are rarely investigated in medicinal inorganic chemistry although they represent structural intermediates between molecules and nanomaterials. We present in this report two strategies towards

A range of bidentate Schiff-base ligands, 2-(cyclohexyliminomethyl)phenol, 2-(cyclopentyl)methyl-5-methylphenol and 5-methyl-2-(phenylethyliminimethyl)phenol, with a variation in steric and electronic properties, were synthesized and coordinated to the fac-{MI(CO)3}+ core (M = Mn, Re). It is illustrated that the nuclearity for the rhenium complexes may be manipulated, i.e., either mono- or dinuclear complexes may be synthesized using virtually the same ligands and synthetic procedures. However, only dinuclear structures were isolated for manganese, in spite of applying very similar synthetic procedures as for rhenium. Four single crystal structures of the fac-[Mn(Sal-CyHex)(CO)3]2 (1), fac-[Mn(5-Me-Sal-CyPent)(CO)3]2 (2), fac-[Re(Sal-CyHex)(CO)3]2 (3), and fac-[Re(5-Me-Sal-EtPh)(CO)3(MeOH)] (4) are reported. The basic geometry was evaluated in detail and strain in the M-O1-M′-O1′ planar inner core was identified, referenced to literature and discussed. The conceptual relevance of these dinuclear complexes is the option of introducing one or two identical or different biologically active moieties into the same complex.

Time-resolved Laue protein crystallography at the European Synchrotron Radiation Facility (ESRF) opened up the field of sub-nanosecond protein crystal structure analyses. There are a limited number of such time-resolved studies in the literature. Why is this? The X-ray laser now gives us femtosecond (fs) duration pulses, typically 10 fs up to ∼50 fs. Their use is attractive for the fastest time-resolved protein crystallography studies. It has been proposed that single molecules could even be studied with the advantage of being able to measure X-ray diffraction from a ‘crystal lattice free’ single molecule, with or without temporal resolved structural changes. This is altogether very challenging R&D. So as to assist this effort we have undertaken studies of metal clusters that bind to proteins, both ‘fresh’ and after repeated X-ray irradiation to assess their X-ray-photo-dynamics, namely Ta6Br12, K2PtI6 and K2PtBr6 bound to a test protein, hen egg white lysozyme. These metal complexes have the major advantage of being very recognisable shapes (pseudo spherical or octahedral) and thereby offer a start to (probably very difficult) single molecule electron density map interpretations, both static and dynamic. A further approach is to investigate the X-ray laser beam diffraction strength of a well scattering nano-cluster; an example from nature being the iron containing ferritin. Electron crystallography and single particle electron microscopy imaging offers alternatives to X-ray structural studies; our structural studies of crustacyanin, a 320 kDa protein carotenoid complex, can be extended either by electron based techniques or with the X-ray laser representing a fascinating range of options. General outlook remarks concerning X-ray, electron and neutron macromolecular crystallography as well as ‘NMR crystallography’ conclude the article.