Am ononuclear Fe II complex, prepared with aB rønsted diacid ligand, H 2 L( H 2 L = 2-[5-phenyl-1H-pyrazole-3-yl] 6-benzimidazole pyridine), shows switchable physical properties and was isolated in five different electronic states.T he spin crossover (SCO) complex, [Fe II (H 2 L) 2 ](BF 4 ) 2 (1 A ), exhibits abrupt spin transition at T 1/2 = 258 K, and treatment with base yields ad eprotonated analogue [Fe II -(HL) 2 ](1 B ), which shows gradual SCO above 350 K. Arange of Fe III analogues were also characterized.[ Fe III (HL)(H 2 L)]-(BF 4 )Cl (1 C )h as an S = 5/2 spin state,w hile the deprotonated complexes [Fe III (L)(HL)],( 1 D ), and (TEA)[Fe III (L) 2 ], (1 E ) exist in the low-spin S = 1/2 state.T he electronic properties of the five complexes were fully characterized and we demonstrate in situ switching between multiple states in both solution and the solid-state.T he versatility of this simple mononuclear system illustrates howproton donor/acceptor ligands can vastly increase the range of accessible states in switchable molecular devices.

Three mononuclear iron(ii) complexes with novel asymmetric tridentate ligands were synthesized and their structures and magnetic properties were studied. The ligand substituents were found to affect the supramolecular packing and spin-crossover properties of the complexes.

A mononuclear FeII complex, prepared with a Brønsted diacid ligand, H2L (H2L=2‐[5‐phenyl‐1H‐pyrazole‐3‐yl] 6‐benzimidazole pyridine), shows switchable physical properties and was isolated in five different electronic states. The spin crossover (SCO) complex, [FeII(H2L)2](BF4)2 (1A), exhibits abrupt spin transition at T1/2=258 K, and treatment with base yields a deprotonated analogue [FeII(HL)2] (1B), which shows gradual SCO above 350 K. A range of FeIII analogues were also characterized. [FeIII(HL)(H2L)](BF4)Cl (1C) has an S=5/2 spin state, while the deprotonated complexes [FeIII(L)(HL)], (1D), and (TEA)[FeIII(L)2], (1E) exist in the low‐spin S=1/2 state. The electronic properties of the five complexes were fully characterized and we demonstrate in situ switching between multiple states in both solution and the solid‐state. The versatility of this simple mononuclear system illustrates how proton donor/acceptor ligands can vastly increase the range of accessible states in switchable molecular devices.

A heterometal Cu 6 Fe wheel molecule, [Cu II 6 Fe III (HL) 6 -(OH) 2 (OCH 3 ) 4 ](NO 3 ) 3 ¢6H 2 O (1¢6H 2 O) (H 2 L = 1-(2-pyridine)-3-(2-pyrrole)acetylacetone) was synthesized by the one-pot reaction of H 2 L with copper and iron sources. X-ray structural analysis reveals that the heptanuclear wheel cluster consists of a central Fe(III) ion surrounded by six Cu(II) ions, linked through methoxo-and hydroxo-bridges. Cryomagnetic studies indicate intramolecular antiferromagnetic interactions were operative. Heterometal polynuclear complexes exhibit physical properties and functions derived from the electronic and magnetic interactions between their constituent transition metal ions, and the search for new compounds with novel properties and functions continues to be an important area of research.1 In the field of biomolecular chemistry, several enzyme models with heterometallic active sites have been investigated.2 It is thus critical to find effective synthetic methods for heterometal clusters in order to better understand the reaction mechanisms of these active sites. Likewise, in materials chemistry, intermetal electronic/magnetic interactions between different metal ions also lead to specific physical properties.3 Heterometal systems can offer a convenient route to designable single-molecule magnets as the magnetic characters of different metal ions can lead to favorable orbital interactions and spin alignment. 4 It is well-known that heterometal mixed-valence systems, such as cyanide-bridged Co-Fe compounds, show external stimuli induced electron-transfer-coupled spin transitions.5 Heterometal complexes are attractive targets in many areas of chemistry and, as a result, new approaches to their controlled-syntheses are needed. Compartment-type ligands, which have distinct coordination sites for different metal ions, are very useful for assembling such species. 6 In recent times, many heterometal complexes have been constructed by exploiting the complexation stability constants of different metal ions. Self-assembly driven syntheses of heterometallic systems have also been serendipitously discovered.7 With these points in mind, advanced synthetic methods should be explored by using appropriate polydentate ligands and reaction conditions. We investigated a range of alkoxo-bridged polynuclear metal clusters, such as homometal [Mn 13 22 These heterometal rings are intensively investigated because of their potential application as spin qubits in quantum computing.In this work, we focus on the asymmetric multidentate bridging ligand, 1-(2-pyridine)-3-(2-pyrrole)acetylacetone (H 2 L), and its complexation reactions with copper and iron sources have been investigated. Herein, the structure and magnetic properties of the obtained heptanuclear Cu 6 Fe wheel complex are reported.To a methanol solution (15 mL) of Cu(NO 3 ) 2 ¢3H 2 O (24.2 mg, 0.1 mmol) was added a methanol solution (10 mL) of H 2 L (21.4 mg, 0.1 mmol) with trimethylamine (27.6¯L, 0.2 mmol). The resulting brown solution was stirred and a methanol ...

A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. (4)) were synthesized. All compounds have one-dimensional zig-zag chain structures with R-dabco cations located between chains. Cryomagnetic studies reveal that 1 and 3 showed intrachain ferromagnetic interactions between Co(II) and Cr(III) ions and metamagnetic behaviour due to interchain antiferromagnetic interactions. Permittivity measurements on compound 4 indicate specific paraelectronic relaxation behaviour originating from the rotational motion of the dabco alkyl substituent.