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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.

Reaction of Co(OAc)2·4H2O and Hsal in a basic MeCN solution affords the hexadecanuclear wheel [Co16(sal)16(OAc)16]·16MeCN (1·16MeCN) that displays ferromagnetic nearest neighbour exchange and has pseudo-calixarene character. Symmetry equivalent wheels self-assemble to form remarkable tubular networks of capsules in the extended structure.

Reaction between Mn(NO3)2.6H2O, Zn(NO3)2.6H2O, 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (H3L) and pyrazole in MeOH under basic conditions leads to the formation of the decanuclear cationic complex [MnIII6MnII2ZnII2(L)2(pyr)4O4(OH)4 (NO3)2(MeOH)2(H2O)4 ](NO3)2.Η2Ο ( 1.Η2Ο). The metallic core of the cluster consists of a central hexagonal-bipyramidal {Mn III4MnII2ZnII 2 } unit connected to two peripheral trivalent Mn centers arranged in a “ trans ” fashion, with one Mn III center lying above and one Mn III center below the hexagonal plane. Replacing Mn(NO 3 ) 2 . 6H 2 O with MnBr 2 . 4H 2 O and repeating the same reaction leads to the formation of the related neutral decanuclear complex [Mn III 6 Mn II 2 Zn II 2 (L) 2 (pyr) 4 O 4 (OH) 4 Br 4 (H 2 O) 2 ] ( 2 ), displaying the same metallic core as 1 . Addition of THF to the reaction mixture that produces ( 2 ) affords the dodecanuclear neutral complex [Mn III 6 Mn II 2 Zn II 4 (L) 2 (pyr) 6 O 4 (OH) 4 Br 4 (H 2 O) 4 ] . 8THF ( 3 . 8THF) whose metallic skeleton retains the central hexagonal-bipyramidal {Mn III 4 Mn II 2 Zn II 2 } unit found in 1 and 2 , but is now connected to two peripheral {Mn III Zn II units. Magnetic susceptibility and magnetization measurements in the T = 2 – 300 K temperature range and in fields up to B = 7.0 T for all three complexes reveal dominant antiferromagnetic exchange interactions.

Use of the 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane ligand, LH

A [Mn18] wheel of wheels is obtained from the reaction of MnBr2·4H2O and LH3 in MeOH. The metallic skeleton reveals two asymmetric [MnIII6MnII2] square wheels connected into a larger wheel via two MnII ions. Magnetic susceptibility and magnetisation data reveal competing exchange interactions, supported by computational studies.

The use of methylalanine in manganese/calcium chemistry has led to the synthesis and characterization of the first manganese/calcium amino acid containing polynuclear clusters.

A [Mn18] wheel of wheels is obtained from the reaction of MnBr2·4H2O and LH3 in MeOH. The metallic skeleton reveals two asymmetric [MnIII6MnII2] square wheels connected into a larger wheel via two MnII ions. Magnetic susceptibility and magnetisation data reveal competing exchange interactions, supported by computational studies.

Ligand design remains key to the synthesis of coordination compounds possessing specific topologies, nuclearities and symmetries that direct targeted physical properties. N,O-chelates based on ethanolamine have been particularly prolific in constructing a variety of paramagnetic 3d transition metal complexes with fascinating magnetic properties. Here, we show that combining three ethanolamine moieties within the same organic framework in the form of the pro-ligand 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (LH3) leads to the formation of two highly unusual Mn wheels. Reaction of Mn(NO3)2·6H2O with LH3 in basic methanolic solutions leads to the formation of [MnIII12MnII4(μ3-O)6(μ-OH)4(μ3-OMe)2(μ-OMe)2(L)4(LH)2(H2O)10](NO3)6(OH)2 (1) and [MnIII10(μ3-O)4(μ-OH)4(μ-OMe)4(L)4(H2O)4](NO3)2 (2), the only difference in the synthesis being the ratio of metal:ligand employed. The structure of the former describes two offset [MnIII6MnII2] square wheels, linked through a common centre, and the latter a single [MnIII10] wheel twisted at its centre, such that the top half is orientated perpendicular to the bottom half. In both cases the L3−/LH2− ligands dictate the orientation of the Jahn-Teller axes of the MnIII ions which lie perpendicular to the triazacyclohexane plane. Direct current magnetic susceptibility and magnetisation data reveal the presence of competing exchange interactions in 1 and strong antiferromagnetic interactions in 2. Given the simplicity of the reactions employed and the paucity of previous work, the formation of these two compounds suggests that LH3 will prove to be a profitable ligand for the synthesis of a multitude of novel 3d transition metal complexes., CJM and TGT thank the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant” (Project Number: 400). EKB thanks the EPSRC for financial support under grant reference numbers EP/I03255X/1 and EP/I031421/1. GL and ME thank the Ministerio de Ciencia e Innovación (RTI2018-094909-J-I00) and CSIC (PIE 201960E002).

A [Mn18] wheel of wheels is obtained from the reaction of MnBr2 and LH3 in MeOH. The metallic skeleton reveals two asymmetric [MnIII6MnII2] squares connected into a wheel via two apical MnII ions. Magnetic susceptibility and magnetisation data reveal competing exchange interactions, supported by computational studies revealing spin frustration.

An amino acid containing octanuclear heterometallic {[MnCa]

This work combines, for the first time, 3D-printing technology and a highly efficient metal organic framework (Ca-MOF) as an electrode modifier to produce a novel fully integrated lab-in-a-syringe device for the sensitive determination of Hg(II) by anodic stripping voltammetry. The specific Ca-MOF ([Ca(H4L)(DMA)2]·2DMA where H6L is the N,N’-bis(2,4-dicarboxyphenyl)-oxalamide and DMA is the N,N-dimethylacetamide) shows an exceptional Hg(II) sorption capability over a wide pH range and its mechanism is elucidated via spectroscopic and X-ray diffraction studies. The voltammetric lab-in-a-syringe device is fabricated through a single-step process using a dual extruder 3D printer and is composed of a vessel integrating two thermoplastic conductive electrodes (serving as the counter and pseudo-reference electrodes) and of a small detachable 3D-printed syringe loaded with a graphite paste/Ca-MOF mixture (which serves as the working electrode). After optimization of the fabrication and operational variables, a limit of detection of 0.6 μg L−1 Hg(II) was achieved, which is comparable or lower than that of existing sensors (plastic 3D-printed, gold and MOF-based electrodes). The adoption of 3D printing technology in combination with the highly efficient Ca-MOF enables the fabrication of a simple, low-cost and sensitive electrochemical sensor for Hg(II), which is suitable for on-site applications.

Employment of H3L2 (=2-(β-naphthalideneamino)-2-hydroxyethyl-1-propanol) in manganese–lanthanide cluster chemistry has led to the isolation of two new isostructural tetrametallic [MnIII2MnIVLnIII] complexes (Ln = Gd, Dy), with the Dy analogue displaying temperature and frequency dependent out-of-phase signals, thus indicating possible single molecule magnetism behaviour.

The use of H3L (= 2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol) in mixed-metal manganese-lanthanide carboxylate cluster chemistry has led to the isolation of two new dodecametallic heteronuclear isostructural [Mn6(III)Ln6(III)] complexes (Ln = Gd, Dy), with the Dy analogue displaying temperature and frequency dependent out-of-phase signals suggesting possible single molecule magnetism behaviour.

Employment of H3L (= 2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol) in mixed-metal manganese-lanthanide cluster chemistry has led to the isolation of five new octametallic heteronuclear isostructural [Mn(III)6Ln(III)2] complexes. More specifically, the reaction of Mn(ClO4)2·6H2O with H3L and the corresponding lanthanide nitrate in MeCN in the presence of a base, NEt3, yielded four complexes with the general formula [Mn(III)6Ln(III)2O2(OH)2(H2O)2(HL)6(NO3)6]·6MeCN·0.5H2O (Ln: Gd, 1·6MeCN·0.5H2O; Tb, 2·6MeCN·0.5H2O; Dy, 3·6MeCN·0.5H2O; Er, 4·6MeCN·0.5H2O). Furthermore, the Y(III) analogue, [Mn(III)6Y(III)2O2(OH)2(H2O)2(HL)6(NO3)6]·6MeCN·0.5H2O (5·6MeCN·0.5H2O), was also synthesized in the same manner. All five clusters describe a central rod-like topology consisting of four face-sharing defective cubane metallic units, forming a planar hexametallic [Mn(III)4Ln(III)2] core, which is further capped by two Mn(III) ions. Dc magnetic susceptibility studies in the 5-300 K range for complexes 1-5 reveal the presence of dominant antiferromagnetic exchange interactions within the metallic clusters, while ac magnetic susceptibility measurements show temperature and frequency dependent out-of-phase signals for the Dy(III) analogue (3·6MeCN·0.5H2O), suggesting potential single molecule magnetism character. Furthermore, the Y(III) analogue yielded a diamagnetic ground-state for the [Mn(III)6] core, thus proving that the SMM character displayed by 3·6MeCN·0.5H2O is due to the presence of the Dy(III) centres.

Employment of H3L (= 2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol) in mixed-metal manganese-lanthanide cluster chemistry has led to the isolation of five new octametallic heteronuclear isostructural [MnIII6LnIII2] complexes. More specifically, the reaction of Mn(ClO4)2·6H2O with H3L and the corresponding lanthanide nitrate in MeCN in the presence of a base, NEt3, yielded four complexes with the general formula [MnIII6LnIII2O2(OH)2(H2O)2(HL)6(NO3)6]·6MeCN·0.5H2O (Ln: Gd, 1·6MeCN·0.5H2O; Tb, 2·6MeCN·0.5H2O; Dy, 3·6MeCN·0.5H2O; Er, 4·6MeCN·0.5H2O). Furthermore, the YIII analogue, [MnIII6YIII2O2(OH)2(H2O)2(HL)6(NO3)6]·6MeCN·0.5H2O (5·6MeCN·0.5H2O), was also synthesized in the same manner. All five clusters describe a central rod-like topology consisting of four face-sharing defective cubane metallic units, forming a planar hexametallic [MnIII4LnIII2] core, which is further capped by two MnIII ions. Dc magnetic susceptibility studies in the 5–300 K range for complexes 1–5 reveal the presence of dominant antiferromagnetic exchange interactions within the metallic clusters, while ac magnetic susceptibility measurements show temperature and frequency dependent out-of-phase signals for the DyIII analogue (3·6MeCN·0.5H2O), suggesting potential single molecule magnetism character. Furthermore, the YIII analogue yielded a diamagnetic ground-state for the [MnIII6] core, thus proving that the SMM character displayed by 3·6MeCN·0.5H2O is due to the presence of the DyIII centres.