engleski

Symmetrical and asymmetrical carbohydrazides: a solid-state and solution study

Carbohydrazide, i.e. 1, 3-diaminourea, represents a versatile building block for the design of symmetrical and asymmetrical urea- based componds. [1] Introduction of specific groups into the structure allows one to fine- tune the desired properties of such systems. For example, pyridine functionalized carbohydrazides proved to be an effective anion receptors, with the ability to stabilize small anion-water clusters.[2] On the other hand, monosubstituted pyridine based derivatives showed to be exquisite ligands for the design of dynamic metal-organic frameworks with intriguing anion-switchable properties.[3] Within this investigation we explored the synthetic opportunities towards selected mono- and bis- substituted carbonohydrazides, both symmetrical and asymmetrical ones, derived from 2, 3- and 2, 4- dihydroxybenzaldehyde, pyridinecarbaldehyde and carbohydrazide.[4] Dihydroxybenzaldehydes in combination with carbohydrazide yielded preferably bissubstituted symmetrical products, whereas in the case of pyridine based aldehydes monosubstituted derivatives were also isolated. The latter were then utilized as starting materials for the synthesis of bissubstituted asymmetrical compounds. All isolated products were thoroughly investigated in the solid-state by means of infrared (IR) spectroscopy, thermal analysis, powder X-ray diffraction (PXRD) and when suitable via single-crystal X-ray diffraction (SCXRD). The results point out to interesting differences in conformation between the symmetrical and asymmetrical derivatives in the solid state. Finally, the obtained compounds were explored in solution by appropriate one- and two- dimensional NMR techniques

carbohydrazide ; symmetrical and asymmetrical ligands ; NMR

nije evidentirano