| Dynamic responsive crystalline molecular materials can respond to external stimuli(e.g.,light,electricity,force,heat,pH,and solvents)to result in structural changes and physical and/or chemical responses,including phase tranistion,dielectric tranistion,ferroelasticity,ferroelctricity,shape change,and luminescent response.Herein,44 saloph Schiff base complexes were used to construct series of crystalline molecular rotors and their structures and dynamic and responsive behaviros were investigated.Part Ⅰ:Nine dumbbell-shaped[Zn(saloph)]2(DABCO)complexes(1-9)were synthesized.The axial DABCO bridging ligand acts as rotator in the compounds.Complex 1 shows the typical dumbbell shape with the[Zn(saloph)]as stator and the DABCO and tert-butyl groups in saloph as rotators.The molecular rotor exhibits a ferroelastic phase tranistion with rare inverse-temperature symmetry breaking which is originated from interactions among the rotators.Complexes 2-4 and 7 show double-site disorders of the DABCO and in 8 and 9 the axial ligand shows obvious thermal vibrations,indicating they are potential molecular rotors.Part Ⅱ:Nineteen crystalline complexes were prepared,including dumbbell-shaped 10-14 and double-T-shaped 15-19 with the general formula of[Zn(saloph)]2(DABCO)(solvent)and[Zn2(saloph)](DABCO)(solvent).Complexes 10-13 show double-site disorders of the DABCO,indicating they are potential molecular rotors.Complexes 14 and its solvated counterparts 14a and 14d are verified to be real molecular rotors.Moreover,there is a solvent guest-induced structural transformation in which the[Zn(saloph)]plate transforms from twisting to an approximate plane.The dihedral angle changes by about 30°,and the conjugation is greatly enhanced to result in a red shift of the fluorescence emission by about 10 nm.These results indicate that complex 14 is a crystalline molecular rotor with tunable luminescence properties.Complexes 15,15a and 15b also show the structural transformation induced by the guest molecule and tunable luminescence properties.The[Zn2(saloph)]plate is transformed from a saddle-like structure to a strong conjugated plane with a dihedral angle change of about 50° and a significant red shift of fluorescence emission of about 30 nm with the emitted light changing from yellow light to orange-red light.Part Ⅲ:Seventeen saloph Schiff-base complexes were synthesized showing various structures.Complexes 20-25 have a T-shaped molecular structure,in which 23-25 are potential molecular rotors.In addition,there is a single-crystal-to-single-crystal structure transition between 23 and 23a with potential solvent guest regulated rotating behavior.Complexes 26-28 contain one-dimensional chains due to the six-coordinated Mn(Ⅲ)ions.Among them,26 is a potential molecular rotor.Complexes 32-35 have an open box structure with the bulky saloph plate as the lid of the box to provide room for the axial DABCO.Complexes 32 and 33 are potential molecular rotors.Complex 34 exhibits a special structural deformation induced by the solvent guests.The Saloph plate changes between two curved forms.The structure of complex 35 is similar to 34,showing confirmed molecular rotor behavior. |
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