Temperature influence on supramolecular structure formation. Synthesis, structure, spectral and DFT studies of Cu(II)-azide systems with symmetric diamines

摘要

Three new Cu(II) complexes, viz. [{Cu_2((1,3-diaminopropane) _2(N_3)_4}_2] (1), [Cu((1,3- diaminopropane)_2(-N_3)_2] (2) and [Cu(en) _2(N_3)_2] (3), with symmetric amines and azide ligands have been synthesized under self-assembly conditions and structurally characterized, towards understanding the influence of temperature in directing the final structure formation. Interestingly, temperature plays a decisive role in the final structure formation, leading to the formation of a tetramer 1 at low temperature (LT) and a monomer 2 at room temperature (RT) in the case of the Cu(II)-1,3-diaminopropane-N_3 system. However, such a temperature influence has not been observed in the case where ethylene diamine is a ligand. Irrespective of the crystallization temperature, the Cu(II)-en-azide system always affords compound 3 only. The stability of both 1 and 2 is further confirmed by Single Point Energy calculations, which corroborate the experimental observations.