The synthesis and characterization of a new octahedral
Zr(IV) complex
of oxygen-depleted
N
,
O
-type calixarene
ligand comprising two distal-functionalized pyrazole rings have been
reported. The cone shape and structure of the prepared complex were
confirmed univocally by single-crystal X-ray diffraction and NMR studies.
The Zr metal lies at 2.091 Å from the plane of the calixarene
ring. This complex has been utilized as an efficient catalyst for
the synthesis of Biginelli adducts, bis(indolyl)methanes, and coumarins.
This complex (Cl
2
Zr–calixarene) showed superior
activity for these multicomponent reactions in comparison to the corresponding
Ti(IV) and Zn(II) analogues. Ferrocene-appended bis(indolyl)methane,
prepared using this catalyst, was also evaluated for its anticancer
activity against the A-172 cell line.