The syntheses, structures, magnetic and magnetocaloric properties of three new hetero-dodecametallic 3d–4f complexes are reported.

An advanced chemistry laboratory project has been developed to introduce final year undergraduate students to organic photocatalyst design using benzo[c][1,2,5]thiadiazole (BTZ) photocatalysts, prepared via a single Suzuki-Miyaura cross-coupling from cheap starting materials, as the example. This project took on a research lab style structure, and over the course of 6 weeks students were tasked to (1) synthesize and study the photophysical properties of three BTZ-based photocatalysts; (2) apply the BTZ photocatalysts to a test photoredox reaction using cheap home-built LEDs, and (3) perform rudimentary computational calculations to rationalize key experimental results.

Reaction of CuCl2·2H2O with p-tert-butylthiacalix[4]arene (H4TC[4]A) affords a [CuII24] cage whose metallic skeleton conforms to a truncated octahedron in which the metal ions are strongly antiferromagnetically coupled. A structurally related [Cu8] cluster can be made using CuBr2 in an otherwise identical reaction.

BODIPY-functionalized host molecules have been used as effective visible-light photosensitizers in the conversion of α-terpinene to ascaridole in the presence of molecular oxygen. Host-guest interactions enhance the effective local concentration of the substrate and singlet oxygen generated by the photosensitizing host. This results in up to a 28-fold increase in the rate of conversion depending on the host employed. A tetramethyl BODIPY analogue, in which guest access to the host cavity is blocked, was also employed to confirm that the cavities do indeed enhance substrate turnover. Whilst the latter photocatalyst is more efficient due to the suppression of nonradiative relaxation pathways associated with rotation of the meso-phenyl substituent, the rate enhancement induced by host-guest binding is not present. Combined, this provides insight for the future design of enhanced systems.

A library of 10 novel organophotocatalysts (ORG-PRCs) has been prepared by the one-pot, two-step ortho-borylation of 4,7-diarylbenzo[c][1,2,5]thiadiazoles (BTZs). The borylation reaction was accompanied by a substantial bathochromic shift in both the absorption and emission spectra (up to 142 nm), allowing these photocatalysts to operate using low-energy green light instead of the high-energy near-UV light that BTZ photocatalysts typically require. The library of photocatalysts was tested using the phosphorylation of quinoline compounds under both batch and recycle flow conditions, achieving up to 40 and 73% conversion, respectively, in 4 h. The versatility of the recycle flow system was further tested by developing a sequential two-step phosphorylation followed by a Minisci coupling procedure using a dual photocatalyst system. This allowed automated production of the target antibacterial phosphorylated quinoline derivative with a total conversion of 64% from abundant, inexpensive, and late-stage modifiable starting materials in a streamlined process.

The heterometallic tricapped trigonal prism [MnIII3Na6(TBC[4])3(CO3)(Cl)(dmso)7]5MeCN ([Mn3Na6]; 15MeCN) and the related heterometallic tetracapped square prism [MnIII4MnII2Na6(bisTBC[4])2(CO3)2(Cl)2(dmf)8(MeOH)1.2(H2O)0.8]6MeCN ([Mn6Na6]; 26MeCN), are isolated using p-tBu-calix[4]arene (H4TBC[4]) and 2,2 '-bis-p-tBu-calix[4]arene (H8-bisTBC[4]), respectively. In the former the MnIII ions sit in the TBC[4] polyphenolic pockets, forming three Mn-TBC[4] metalloligands that cap the square faces of the prism, whose vertices contain the six Na ions. Introduction of the bis-calix[4]arene enables expansion of the main building block from three Mn-TBC[4] metalloligands in 1 to four Mn-TBC[4] metalloligands in 2. The result is the formation of a square prism of Na/MnII ions, with four of the square faces capped with MnIII ions. Dc magnetic susceptibility and magnetisation measurements reveal paramagnetism in 1 and weak antiferromagnetic exchange interactions in 2.

A survey of the literature and the Cambridge Structural Database reveals thirty nine p-tert-butylcalix[8]arene-supported transition (3d, limited to V-Cu) and lanthanide metal complexes ranging in nuclearity from one to eighteen, twenty of which are homometallic and nineteen of which are heterometallic. We provide a review of the coordination chemistry of these complexes, including our own work in the area. We also provide our thoughts and perspectives on the common structural themes observed, identify gaps in knowledge and evaluate how that may inform and direct future synthetic efforts. What is clear is that the coordination chemistry of H8TBC[8] with paramagnetic metal ions remains hugely underexplored.

Calix[n]arenes offer ideal chemical functionality through the polyphenolic lower rim to construct nano-sized coordination clusters with lanthanide (Ln) metal ions (e.g., Nd-10(III), Gd-8(III)). However, the number of metal centers they can accommodate is still limited compared to that achievable with smaller ligands (e.g., Gd-140(III), Gd-104(III)). Here, we exploit a combination of the "anion template strategy" and "templating ligands" to synthesise three highly symmetric (D-3h, trigonal planar) Ln(18)(III) (Ln = La, Nd, and Gd) systems, representing the largest calix[n]arene-based coordination clusters yet. The Ln(18)(III) fragment is templated by a chloride anion located at the center of the cluster, wherefrom twelve mu(3)-OH- ligands bind 'internally' to the eighteen Ln(III) ions. 'Externally' the metallic skeleton is connected by p-tert-butylcalix[8]arene, oxo, chloro and carbonate ligands. The crystal packing in the lattice reveals large cylindrical channels of similar to 26 & Aring; in diameter, whose pore volume corresponds to similar to 50% of the unit cell volume (using a 1.2 & Aring; spherical probe radius). Magnetic measurements reveal the predominance of weak antiferromagnetic exchange in the Gd analog. Heat capacity data of Gd-18(III) reveal a high magnetic entropy with -Delta S-m = 23.7 J K-1 kg(-1), indicating potential for engineering magnetic refrigerant materials with calix[8]arenes.

Benzo[c][1,2,5]thiadiazole PIM-EA-TB copolymers are solution processable and microporous photosensitisers that can be deposited onto glass beads for use in a fixed bed continuous flow photoreactor.

Interaction of the lanthanide nitrates M(NO3)3 (M = Gd, Eu) with methylcucurbit[5]uril (Me10Q[5]) in the presence of transition metal chlorides (ZnCl2 and FeCl3) in acidic media resulted in the isolation of the complexes [Me10Q[5]Gd(H2O)2Cl Gd(H2O)6](ZnCl4)2∙Cl∙8.9H2O (1) and [Me10Q[5]Eu(H2O)3Cl(H3O)](FeCl4)3 (2). The molecular structures of 1 and 2 have been determined by single crystal X-ray crystallography, and reveal discrete complexes which are involved in dense stacking with adjacent Me10Q[5]s linked via H-bonding and/or metal anions resulting in a supramolecular assembly.

The solvothermal reaction of FeCl2 ⋅ 4H2O and H4TBC[4] in a basic dmf/EtOH solution affords an [FeIII 18] Keplerate conforming to a stellated cuboctahedron. Magnetic and heat capacity measurements reveal spin frustration effects arising from the high symmetry. A crossover between inverse and direct magnetocaloric effects is observed at ~10 K for applied-field changes lower than 3 T.

Here we report the controlled self-assembly of vanadium-seamed metal-organic nanocapsules with specific metal oxidation state distributions. Three supramolecular assemblies composed of the same numbers of components including 24 metal centers and six pyrogallol[4]arene ligands were constructed: a VIII24L6 capsule, a mixed-valence VIII18VIV6L6 capsule, and a VIV24L6 capsule. Crystallographic studies of the new capsules reveal their remarkable structural complexity and geometries, while marked differences in metal oxidation state distribution greatly affect the photoelectric conversion properties of these assemblies. This work therefore represents a significant step forward in the construction of intricate metal-organic architectures with tailored structure and functionality.

Quaternary phosphonium salts are popular candidates used in many chemical transformations and synthetic chemistry, notably in catalysis. We have examined the single crystals of two bulky phosphonium compounds, tetra([1,1′-biphenyl]-4-yl) phosphonium dicyanamide (C48H36P+·N(CN)2−, compound 1), and tetra([1,1′-biphenyl]-4-yl) phosphonium bromide hydrate (C48H36P+·Br−, CH3CN, H2O, compound 2), and herein report the structural properties for the compounds with an emphasis on the influence of the ion-ion interaction towards self-assembly; the overall self-assembly for both structures is very similar, with subtle differences in the cell parameters. The symmetrical tetra ([1,1′-biphenyl]-4-yl) phosphonium cations in both compounds self-assembled to form robust stacked columns in the solid-state, with voids occupied by anions or solvent molecules. Quantitative examination of intermolecular interactions using Hirshfeld surface analysis found that classical and non-classical hydrogen bonding appears to be the dominant contributor in stabilizing the self-assembly in both cases. The present work can not only benefit in understanding the mutual interaction between the sterically encumbered tetra ([1,1′-biphenyl]-4-yl) phosphonium cations and between counterions, but also provide insights for the self-assembled arrays in the solid-state.

Here we report that a Cu2+-seamed coordination nanocapsule can serve as an efficient semiconductor photocatalyst for molecular oxygen activation. This capsule was constructed through a redox reaction facilitated self-assembly of cuprous bromide and C-pentyl-pyrogallol[4]arene. Photophysical and electrochemical studies revealed its strong visible-light absorption and photocurrent polarity switching effect. This novel molecular solid material is capable of activating molecular oxygen into reactive oxygen species under simulated sunlight irradiation. The oxygen activation process has been exploited for catalyzing aerobic oxidation reactions. The present work provides new insights into designing nonporous discrete metal-organic supramolecular assemblies for solar-driven molecular oxygen activation.

Reaction of 2,2'-bis-p-tBu-calix[4]arene (H8L) with Cu(NO3)2·3H2O and N-methyldiethanolamine (Me-deaH2) in a basic dmf/MeOH mixture affords [CuII16(L)2(Me-dea)4(μ4-NO3)2(μ-OH)4(dmf)3.5(MeOH)0.5(H2O)2](H6L)·16dmf·4H2O (4), following slow evaporation of the mother liquor. The central core of the metallic skeleton describes a tetracapped square prism, [Cu12], in which the four capping metal ions are the CuII ions housed in the calix[4]arene polyphenolic pockets. The [CuII8] square prism is held together "internally" by a combination of hydroxide and nitrate anions, with the N-methyldiethanolamine co-ligands forming dimeric [CuII2] units which edge-cap above and below the upper and lower square faces of the prism. Charge balance is maintained through the presence of one doubly deprotonated H6L2- ligand per [Cu16] cluster. Magnetic susceptibility measurements reveal the predominance of strong antiferromagnetic exchange interactions and an S = 1 ground state, while EPR is consistent with a large zero-field splitting.

Reaction of Gd(OAc)3·4H2O, salicylaldehyde and CH3ONa in MeCN/MeOH affords [Gd12Na6(OAc)25(HCO2)5(CO3)6(H2O)12]·9H2O.0.5MeCN (1·9H2O.0.5MeCN), whose structure describes a quadruple-wheel consisting of two {Na3} and two {Gd6} rings. The magnetic properties of 1 reveal very weak antiferromagnetic interactions between the GdIII ions, which give rise to a record magnetocaloric effect at low applied magnetic fields and low temperatures. The magnetic entropy change reaches -ΔSm= 29.3 J kg-1 K-1 for full demagnetization from B = 1 T at T = 0.5 K.

The solvothermal reaction of Zn(NO3)2·4H2O, 1-OH-2-naphthaldehyde, and 2-methylalanine (mAla) in MeOH leads to the formation of complex {[ZnL1]}2n (1) (H2L1 = the Schiff-base resulting from the reaction of 1-OH-2-naphthaldehyde and mAla) in good yields. The structure of the neutral species, as determined by single-crystal crystallography, describes a two-dimensional coordination polymer, with repeating {Zn2} units bridged by syn, anti-carboxylate groups of the Schiff-base ligands. Repeating the same reaction using glycine (gly) instead of mAla leads to the formation of complex {[ZnL2]·0.33MeOH}3n (2.0.33MeOH) (H2L2 = the Schiff-base resulting from the reaction of 1-OH-2-naphthaldehyde and gly), again in good yields. Complex 2 describes a three-dimensional coordination polymer based on {Zn2} building blocks, arranged by anti, anti-carboxylate groups in a 3D motif. Complexes 1 and 2 were found to strongly emit at ~435 nm (λexc = 317 nm) both in solution and solid state, with complex 2 displaying a slightly longer lifetime of τav = 2.45 ns vs. τav = 2.02 ns for 1.

Reaction of Gd(OAc)3 center dot 4H2O, salicylaldehyde and CH3ONa in MeCN/MeOH affords [Gd12Na6(OAc)25(HCO2)5(CO3)6(H2O)12]center dot 9H2O.0.5MeCN (1 center dot 9H2O.0.5MeCN), whose structure describes a quadruple-wheel consisting of two {Na3} and two {Gd6} rings. The magnetic properties of 1 reveal very weak antiferromagnetic interactions between the GdIII ions, which give rise to a record magnetocaloric effect at low applied magnetic fields and low temperatures. The magnetic entropy change reaches -Delta Sm= 29.3 J kg-1 K-1 for full demagnetization from B = 1 T at T = 0.5 K.

Regioselective stepwise phenylation of 4,7-diarylbenzo[c][1,2,5]thiadiazole fluorophores has been achieved through a facile one-pot, three-step synthetic strategy involving sequential borylation, hydroxydechlorination and Suzuki-Miyaura cross-coupling reactions. Crucial to the selectivity was the use of BCl3 to regioselectively install a boronic acid group in the ortho-position of only one of the diaryl groups. The subsequent introduction of ortho-phenyl groups through Suzuki-Miyaura cross-coupling gave rise to twisted structures with hindered intramolecular rotation, providing a structural lever with which the fluorophore absorption and emission properties could be adjusted.