A series
of group 10 complexes featuring chelating tridentate bis-aryloxide
N-heterocyclic carbenes were synthesized and characterized by using
different techniques. Ni(II), Pd(II), and Pt(II) complexes were isolated
in good yields by straightforward direct metalation of the corresponding
benzimidazolium or imidazolium precursors in a one-pot procedure.
All of the compounds were fully characterized, including single-crystal
X-ray diffractometric determination for three of the derivatives.
In the solid state, the complexes adopt a typical square-planar coordination
geometry around the platinum atom, sizably distorted in order to comply
with the geometrical constraints imposed by the bis-aryloxide N-heterocyclic
carbene ligand. For platinum and palladium derivatives, a joint experimental
and theoretical characterization was performed in order to study the
optical properties of the newly prepared complexes by means of electronic
absorption and steady-state and time-resolved photophysical techniques
as well as density functional theory (DFT) and time-dependent DFT
in both vacuum and solvent. When the temperature was lowered to 77
K in frozen glassy matrix, three platinum complexes showed broad and
featureless, yet weak, photoluminescence in the green region of the
visible spectrum with excited-state lifetimes on the order of a few
microseconds. On the basis of joint experimental and computational
findings and literature on platinum complexes, such emission was assigned
to a triplet-manifold metal−ligand-to-ligand charge transfer
(3MLLCT) transition.
A simple procedure for the preparation of Nheterocyclic carbene platinum complexes with a nitrogenbased neutral ligand in trans geometry is presented. The lability of a trans pyridine ligand in an N-heterocyclic carbene− Pt(II) − pyridine complex, namely, (3-be nzyl-1methylimidazolylidene)PtI 2 (pyridine), 2, was probed by a displacement reaction with various nitrogen-based ligands (e.g., amines, hydrazine, amino esters, and peptides) to yield the corresponding complexes, which could be easily isolated by column chromatography. Two representative complexes could be characterized by X-ray crystallographic studies. This strategy allows generating diversity in metallodrug candidates. Preliminary results of the biological effects on various human cancer cells and comparison wih cisplatin are reported.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.