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Complexation of Fe[ClO4]2·6H2O by 1 equiv. 2,6-bis((4S)-4-phenyl-4,5-dihydrooxazol-2-yl)pyridine ((S)-L1Ph) and 2,6-bis((4R)-4-phenyl-4,5-dihydrothiazol-2-yl)pyridine ((R)-L2Ph) cleanly affords [Fe((S)-L1Ph)((R)-L2Ph)][ClO4]2; [Fe((R)-L1iPr)((S)-L2iPr)][ClO4]2 (L1iPr = 2,6-bis(4-isopropyl-4,5-dihydrooxazol-2-yl)pyridine; L2iPr = 2,6-bis(4-isopropyl-4,5-dihydrothiazol-2-yl)pyridine) was prepared by a similar route. The compounds exhibit thermal spin-crossover in solution, at temperatures midway between the corresponding [Fe((R)-L1R)((S)-L1R)][ClO4]2 and [Fe((R)-L2R)((S)-L2R)][ClO4]2 (R = Ph or iPr) species. The spin states of [Fe(LR)(bimpy)][ClO4]2 and [Fe(LR)(bpp)][ClO4]2 (LR = L1R or L2R; bimpy = 2,6-bis(1H-benzimidazol-2-yl)pyridine; bpp = 2,6-di(pyrazol-1-yl)pyridine) are also reported, with most examples exhibiting gradual spin-crossover in solution and the solid state. Although some products undergo partial ligand exchange in solution by 1H NMR, their solution T½ values appear unaffected by this and correlate well with their spin state energies from gas phase DFT calculations. The high-spin state of [Fe(L2R)(bpp)]2+ is more stabilised than expected, compared to the other [Fe(LR)L]2+ complexes studied (L = bimpy, bpp or terpy). That is explained by an interplay between the relative σ-basicities and π-acidities of the two ligands in each molecule. The steric influence of their phenyl or isopropyl 'R' substituents stabilises the heteroleptic complexes by up to 5 kcal mol−1, compared to analogues lacking these groups. [ABSTRACT FROM AUTHOR]

The following iron(II) complexes of 2,6- bis(oxazolinyl)pyridine (PyBox; LH) derivatives are reported: [Fe( LH)2][ClO4]2 ( 1); [Fe(( R)- LMe)2][ClO4]2 (( R)- 2; LMe=2,6- bis{4-methyloxazolinyl}pyridine); [Fe(( R)- LPh)2][ClO4]2 (( R)- 3) and [Fe(( R)- LPh)(( S)- LPh)][ClO4]2 (( RS)- 3; LPh=2,6- bis{4-phenyloxazolinyl}pyridine); and [Fe(( R)- L iPr)2][ClO4]2 (( R)- 4) and [Fe(( R)- L iPr)(( S)- L iPr)][ClO4]2 (( RS)- 4; L iPr=2,6- bis{4- isopropyloxazolinyl}pyridine). Solid ( R)- 3⋅MeNO2 exhibits an unusual very gradual, but discontinuous thermal spin-crossover with an approximate T [ABSTRACT FROM AUTHOR]

Correction for 'Heteroleptic iron(II) complexes of chiral 2,6-bis(oxazolin-2-yl)-pyridine (PyBox) and 2,6-bis(thiazolin-2-yl)pyridine ligands – the interplay of two different ligands on the metal ion spin state' by Namrah Shahid et al., Dalton Trans., 2022, 51, 4262–4274, DOI: 10.1039/d2dt00393g. [ABSTRACT FROM AUTHOR]

The cover image compares the molecular spin states of two diastereomers of a spin‐crossover iron(II) complex. Solution‐phase magnetic measurements show the low‐spin state of the heterochiral (meso) diastereomer is stabilized relative to its homochiral (rac) congener. This reflects a steric clash between phenyl substituents in the rac isomer, which occupies two diagonal quadrants in the molecule. The resultant twisting of the ligand conformation and metal‐coordination sphere explains the observed reduction in the ligand field. More information can be found in the Full Paper by M. A. Halcrow et al. on page 9067. [ABSTRACT FROM AUTHOR]