Enhanced and Heteromolecular Guest Encapsulation in Nonporous Crystals of a Perfluorinated Triketonato Dinuclear Copper Complex.

The flexible host framework of a perfluorinated mononuclear copper complex, [Cu(L ) ] (1, HL =3-hydroxy-1,3-bis(pentafluorophenyl)-2-propen-1-one), with a CuO core reversibly encapsulated several organic guest molecules through electrostatic interactions in its crystals. Hence, the corresponding dinuclear complex, [Cu (L ) ] (2, H L =1,5-dihydroxy-1,5-bis(pentafluorophenyl)-1,4-pentadien-3-one), was prepared to enhance guest recognition and the ability to separate molecular mixtures. Complex 2 comprises a Cu O core and four pentafluorophenyl groups. In crystal 2, cavities are formed on the axial sites of the metal core that are surrounded by pentafluorophenyl groups. The crystal of 2 encapsulates various guest molecules, that is, benzene (3), toluene (4), xylene (5), mesitylene (6), durene (7), and anisole (8). X-ray crystallographic and thermogravimetric (TG) studies show that three guest molecules are present in the crystal cavities. The number of guest molecules found in complex 2 was higher than that in complex 1, for example, (2) ⋅(6) >1⋅(6) , (2) ⋅(7) >1⋅7, or 2⋅(8) >1⋅(8) . Naphthalene (9), was encapsulated in 2 to give 2⋅(9) , but not in 1. In the crystal of complex 2, heteromolecular guest encapsulation was confirmed, designated as 2⋅(3) ⋅9. TG analysis indicates that the thermal stability of the guest-included crystals of 2 is higher than that of 1.