Synthesis, Crystal Structures, and Dual Donor Luminescence Sensitization in Novel Terbium Tetracyanoplatinates
dataset
posted on 2012-11-19, 00:00 authored by Philip
A. Smith, Carlos Crawford, Nuquie Beedoe, Zerihun Assefa, Richard E. SykoraA series of novel terbium tetracyanoplatinate compounds
all incorporating
tridentate 2,2′:6′2″-terpyridine (terpy) or 4′-chloro-2,2′:6′2″-terpyridine
(terpy-Cl) were synthesized and used to investigate the phenomenon
of dual-donor sensitization of Tb3+. Judicious choice of
the Tb3+ salt and reaction conditions results in the isolation
of {Tb(terpy)(H2O)2(NO3)Pt(CN)4}·CH3CN (1A), {Tb(terpy)(H2O)2(NO3)Pt(CN)4}·3.5H2O (1B), {Tb(terpy-Cl)(H2O)2(NO3)Pt(CN)4}·2.5H2O (2), [Tb(terpy)(H2O)2(CH3COO)2]2Pt(CN)4·4H2O (3), or [Tb2(terpy)2(H2O)2(CH3COO)5]2Pt(CN)4·7H2O (4). The compounds 1A, 1B, and 2 contain one-dimensional polymeric
structures with bridging of [Tb(L)(NO3)(H2O)2]2+ (L = terpy or terpy-Cl) moieties by cis-bridging
tetracyanoplatinate (TCP) anions as determined via single-crystal
X-ray diffraction studies. Both 3 and 4,
however, contain Tb3+ coordinated by multiple acetate ligands
and terpy, but not TCP, and are classified as zero-dimensional complex
salts. Platinophilic interactions that dominate tetracyanoplatinate
structural chemistry are present in the form of dimeric units in the
polymeric compounds, but are totally absent in 3 and 4. The structural differences result in markedly different
luminescence properties for the two classes of compounds. All of the
polymeric compounds display efficient donor–acceptor intramolecular
energy transfer (IET) from the terpy unit to the Tb3+ ion.
Although the TCP units are also directly coordinated to the Tb3+ ion in the three polymers, only in 1B and 2 are the Pt···Pt interactions strong enough
to provide MMLCT bands of appropriate energy to result in a dual-donor
effect to the Tb3+ sensitization. Even in these cases,
TCP does not efficiently sensitize the Tb3+, rather a broad
band TCP emission results. However, terpy and acetate ligands are
bonded directly to the Tb3+ ion in 3 and 4 and provide a strong dual-donor sensitization effect as
evidenced by the large QY for Tb3+.
