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The field of anion supramolecular chemistry has received more and more attention in recent years. Anions with diverse types and geometries have been widely used for the synthesis of ionic spin crossover (SCO) complexes. This review is devoted to anion effects on the molecular, supramolecular structures and magnetic properties of discrete SCO compounds. Firstly, typical anions used in the synthesis of these compounds are briefly summarized according to their various geometries. This is followed by a collection of representative examples of anion‐based SCO compounds, whose SCO properties are analyzed in terms of supramolecular interactions, geometry and charge of anions. In the third part, anion effects on SCO complexes of different kinds of metal centers and ligands are outlined and finally remarks on the synthesis new type of ionic SCO complexes in the future are described. [ABSTRACT FROM AUTHOR]

• A series of three new mononuclear manganese(III) Schiff-base complexes. • The change of substituents or anions affects the spin crossover (SCO) properties. • Magnetic measurements provided firm evidence for the cooperative SCO effects in complexes 2 and 3 , while complex 1 persists in the HS state. • Complex 3 exhibits a surprisingly gradual SCO process with a hysteresis width of 6 K at lower temperature. The flexible hexadentate Schiff-base ligands (R-sal-N-1,5,8,12)2− can be easily obtained by modifying the different substituents at the 5 or 3,5 positions on the phenyl rings of the salicylaldehyde. We report in this paper the syntheses, crystal structures and magnetic properties of three new mononuclear manganese(III) complexes [Mn(R-sal-N-1,5,8,12)]Y (R = 5-H, Y = BF 4 (1); R = 3,5-diCl, Y = SbF 6 (2); R = 5- t Bu, Y = ClO 4 (3)). All the complexes have an analogous monocationic MnN 4 O 2 surrounding offered by the flexible hexadentate ligand in a distorted octahedral geometry. Magnetic susceptibility measurements demonstrated that complex 1 maintains a high-spin (HS) state between 2 and 400 K due to the closing packing, while complex 2 shows a cooperative and complete one-step thermo-induced spin state switching with T 1/2 of 194 K. As for complex 3 , single-crystral X-ray structural studies show the existence of a large amount of HS manganese(III) ions at 100 K and it exhibits a surprisingly gradual SCO process with a hysteresis width of 6 K at lower temperature. [ABSTRACT FROM AUTHOR]

The crystal structures and magnetic properties of three Mn(III) Schiff-base complexes [Mn(3-OMe-sal-N-1,5,8,12)]AsF 6 ·H 2 O (1) , [Mn(4-OMe-sal-N-1,5,8,12)]AsF 6 ·H 2 O (2) and [Mn(5-OMe-sal-N-1,5,8,12)]AsF 6 (3) have been studied. Complexes 1 and 2 show gradual SCO behavior. The transition temperatures of 2 is 98 K higher than that of 1. Due to the absence of crystallizing solvent water molecule, complex 3 maintains a HS state in the test temperature range. [Display omitted] Spin crossover (SCO), as a molecular bistable phenomenon, has attracted extensive interest. In this paper, the syntheses, crystal structures and magnetic properties of three Mn(III) hexadentate Schiff-base complexes [Mn(3-OMe-sal-N-1,5,8,12)]AsF 6 ·H 2 O (1) , [Mn(4-OMe-sal-N-1,5,8,12)]AsF 6 ·H 2 O (2) and [Mn(5-OMe-sal-N-1,5,8,12)]AsF 6 (3) have been reported. The substituent positions of ligands and solvent molecules have a cooperative effect on SCO behavior. Complex 1 shows a complete SCO between the high-spin (HS, S = 2) and low-spin (LS, S = 1) states without thermal hysteresis, and complex 2 shows a gradual incomplete SCO behavior. The transition temperatures of 2 (T 1/2 = 241 K) is 98 K higher than that of 1 (T 1/2 = 143 K), which indicates that the ligand field strength of (4-OMe-sal-N-1,5,8,12)2– is stronger than that of (3-OMe-sal-N-1,5,8,12)2–. Due to the absence of crystallizing solvent water molecule, complex 3 maintains a HS state in the test temperature range. [ABSTRACT FROM AUTHOR]

• Four new MnIII hexadentate Schiff base complexes. • The change of substituent position affects the spin crossover property. • The nature and geometry of the counter anions play a dominant role in the supramolecular interactions. • Hirshfeld analysis. In this paper, the syntheses, crystal structures and magnetic properties of spin crossover (SCO) salts of formula [Mn(4-OMe-sal-N-1,5,8,12)]SbF 6 ‧0·45H 2 O (1), [Mn(3-OMe-sal-N-1,5,8,12)]SbF 6 ‧H 2 O (2), [Mn(4-OMe-sal-N-1,5,8,12)]ClO 4 ‧H 2 O (3) and [Mn(3-OMe-sal-N-1,5,8,12)]Br (4) have been reported. Magnetic susceptibility measurements demonstrate that complex 1 shows a gradual one-step SCO between the high-spin (HS, S = 2) and low-spin (LS, S = 1) states without thermal hysteresis. The transition temperatures T 1/2 of the 4-OMe-SbF 6 (1) salt estimated from the magnetic susceptibility measurement is 213 K. As for complex 2, π···π stacking interactions lead to more close stacking which hinder the flexibility of the whole ligand and it is stable in the HS state in the temperature range of 2–300 K. Both complexes 3 and 4 exhibit incomplete spin crossover behavior. These results are consistent with Hirshfeld analysis. Electrochemical analysis indicates that the change of methoxy‑substituent position from 4 to 3 decreases the electron density on the metal center. [ABSTRACT FROM AUTHOR]

The reaction of Mn(Ⅱ) salts prepared with (5-I-sal-N-1,5,8,12)2− ligand where the hexadentate ligand is the product of the reaction of 5-iodosalicylaldehyde and N,N'-bis(3-aminopropyl)ethylenediamine in situ in MeOH/EtOH provided five complexes, [Mn(5-I-sal-N-1,5,8,12)]Y (Y = PF 6 − (1), AsF 6 − (2), SbF 6 − (3), BF 4 − (4), ClO 4 − (5)). All complexes crystallize without crystallizing solvents, except 4 with a H 2 O solvent molecule. Different structural features and magnetic profiles have been observed in complexes 1 − 3. Owing to the cooperativity of the N H···F and N H···I hydrogen bonds and I···π, I···F interactions, complexes 1 and 3 persist in the HS state at 2 − 400 K while complex 2 shows a gradual SCO with T 1/2 is about 265 K. Hirshfeld face analysis reveals that the presence of different interactions in complexes 1 − 3. With decreasing the temperature, complex 4 undergoes an almost full SCO with T 1/2 = 272 K, while complex 5 shows an incomplete SCO and remains 50% HS state until 30 K. [ABSTRACT FROM AUTHOR]

The interplay of host‐guest interactions and controlled modulation of spin‐crossover (SCO) behavior is one of the most exploited topics regarding data storage, molecular sensing, and optical technologies. This study examines the effect of solvents on the spin‐crossover (SCO) behavior of manganese(III) complexes [Mn(sal‐N‐1,5,8,12)]I•S (S=CH3OH, C2H5OH, CH3CN) (1) and [Mn(sal‐N‐1,5,8,12)]I3 (2), where (sal‐N‐1,5,8,12)2− is 2,2′‐((1E,13E)‐2,6,9,13‐tetraazatetradeca‐1,13‐diene‐1,14‐diyl)diphenol synthesized by salicylaldehyde and 1,2‐bis(3‐aminopropylamino)ethane. The complexes, crystallizing in orthorhombic or monoclinic systems, exhibit similar supramolecular arrangements with one‐dimensional cationic chains at low temperatures. Magnetic studies reveal that solvent inclusion sharpens the SCO transition and lowers the transition temperature. Specifically, 1⋅CH3OH shows a 13 K thermal hysteresis due to methanol's mobility through the channels in the cationic framework. Although the solvent‐free compound was not obtained, compound 2 with a linear I3− anion was synthesized, displaying extensive cation‐anion contacts and a distinct 13 K thermal hysteresis upon heating due to altered intermolecular cooperativity. This emphasizes the significant role of solvent introduction and variation in crystal packing and their impact on the SCO properties. [ABSTRACT FROM AUTHOR]

In this paper, we introduce the halogen substituents (F, Cl, Br, I) to explore their influence on the structures and SCO properties of the Mn(III) complexes. [Display omitted] Six mononuclear Mn(III) complexes with hexadentate Schiff-base ligand, the products of the reaction between a N,N ′-bis(3-aminopropyl)ethylenediamine or triethylenetetramine and 5-X-salicylaldehyde have been synthesized: the I− salts of complexes 1 – 3 exhibit a gradual SCO behavior, [Mn(5-Cl-sal-N-1,5,8,12)]I (1) shows a nearly complete SCO with T 1/2 = 125 K, whereas [Mn(5-Br-sal-N-1,5,8,12)]I (2) and [Mn(5-I-sal-N-1,5,8,12)]I (3) show a gradual and incomplete SCO above room temperature. [Mn(5-F-sal-N-1,4,7,10)]I (4) predominantly remains HS state at all temperatures. [Mn(5-I-sal-N-1,5,8,12)]NO 3 (5) and [Mn(5-F-sal-N-1,5,8,12)]NO 3 (6) show an almost full conversion to the HS state and a more gradual SCO having the T 1/2 value of 282 K for 5 and 159 K for 6, respectively. [ABSTRACT FROM AUTHOR]