Ir(I)–Bi(III) Donor–Acceptor Adducts Stabilized by Dispersion Interactions between the Metal Pincer Ligands and Their Possible Self-Assembly Forming Molecular 1D Semiconductors

Structure,
stability, and electronic properties of the bimetallic
{[IrI(terpy)(Me)]-[BiIIINNN]}n monomeric, oligomeric, and polymeric structures (n = 1–3 and ∞; terpy = terpyridine; Me = methyl; BiNNN
= bismuth triamide) and their derivatives (designated as (Bi·Ir)n structures) were studied theoretically by
DFT cluster and periodic calculations. Stable Bi·Ir adducts (monomers)
were formed with short Bi–Ir bonds (<2.7 Å) and Gibbs
free binding energies larger than 20 kcal/mol for all systems. The
substitution of the pincer ligands of Ir(I) and Bi(III) complexes
by the electron-donating (NH2) and electron-withdrawing
(NO2, F, CF3) groups, respectively, enhanced
the Ir → Bi charge transfer, substantially stabilizing the
Bi·Ir monomers. The monomers from the unsubstituted complexes
can be considered as dispersion stabilized adducts, and they may form
spontaneously (Bi·Ir)n layered oligomers/polymers
with semiconducting properties. The self-assembly of monomers into
oligomers/polymers is hindered by bulkier protecting groups on the
Bi(III) complex, such as tBu and SiMe3.