Formation of adaptable molecular clefts based on self-assembly of lipophilic Fe(II) triazole complexes and their spin crossover characteristics

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Lipophilic modification of one-dimensional metal complexes provide self-assembly of molecular wires which exhibit unique solution properties not accessible from conventional inorganic, polymer or supramolecular chemistry. In this study, we focused on the creation of molecular binding clefts on the surface of lipophilic linear metal complexes.Supramolecular Fe(II) complexes bridged by dodecyloxypropyl-1, 2, 4-triazole was newly developed. It exhibited sluggish spin crossover behavior in the solid state. Co-casting of equimolar dodecanol or tetradecanol with the Fe(II)triazole complex afforded composite films in which alcohol molecules were bound to the complex via van der Waals interactions and ionic hydrogen bonding. Interestingly, thermal hysteresis was induced in the spin crossover characteristics of ternary cast films. By doping alcohol molecules, lamellar structures at lower temperatures (LS state) were converted to hexagonal structures at higher temperatures (HS state), and such s … More tructural transformation of basic structures caused generation of bistability. This study provides a first example of supramolecular control on the thermal spin crossover phenomena. This concept was further applied to the combination of Fe(II) triazole complexes and liquid crystals, which demonstrated the formation of spin crossover liquid crystalline gels.To photoregulate the morphology of 1D Fe(triazole)3 complexes, azobenzene chromophores were introduced. UV light irradiation of the azobenzene-containing Fe(II) triazole complex in a yellow chlorocyclohexane gel caused fluidization into an orange-colored solution. In AFM, parallel-aligned rod-like structures in nanosheets were observed for the gel samples. UV irradiation causes structural transformation to undulating molecular wire structures. 4 Finally, electrochemical control on organogels was investigated. Cyclic voltammetry indicates that linear Fe(II) triazole complex display reversible oxidation and reduction in chloroform. Their gel-to-sol transition characteristics are controllable based on oxidation/reduction of iron ions. Thus, stimuli-responsive molecular wires of coordination chains were created, which showed unique physical properties. Less