Synthesis, Crystal Structures, and Dual Donor Luminescence Sensitization in Novel Terbium Tetracyanoplatinates

Abstract

A 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 Tb(3+). Judicious choice of the Tb(3+) 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 Tb(3+) 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 Tb(3+) ion. Although the TCP units are also directly coordinated to the Tb(3+) 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 Tb(3+) sensitization. Even in these cases, TCP does not efficiently sensitize the Tb(3+), rather a broad band TCP emission results. However, terpy and acetate ligands are bonded directly to the Tb(3+) ion in 3 and 4 and provide a strong dual-donor sensitization effect as evidenced by the large QY for Tb(3+).

Fabrication of multi-pyridine functionalized carbon nanotubes as versatile coordination nano-linkers

“…This redox wave could be designated to one electron transfer of MWNT-PVP-Fe(II)TPy 4 MWNT-PVP-Fe(III)TPy, and in agreement with that observed in the Langmuir-Blodgett lms of Fe-TPy complexes. 34 A smaller potential separation between the cathodic and anodic potentials was found in the present work than in the Langmuir-Blodgett lms, 35 which may be attributed to the co-existing MWNTs that could act as an electrical wire to reduce lm resistance.…”

Lanthanide Photoluminescence in Heterometallic Polycyanidometallate-Based Coordination Networks

“…Following the promising optical properties of 3D Ln III –[Pt II (CN) 4 ] 2− networks, a considerable number of the related d–f cyanido-bridged coordination polymers revealing photoluminescent functionalities were reported (Table 2) [80,81,82,83,84,85,86,87,88]. The insertion of 2,2’:6’2”-terpyridine (terpy) into the self-assembled Ln III –Pt II system resulted in the one-dimensional [Ln III (terpy)(H 2 O) 2 (NO 3 )][Pt II (CN) 4 ]· n (solvent) (Ln = Eu, Tb) zig-zag chains (Figure 4a) [81,87].…”

“…The insertion of 2,2’:6’2”-terpyridine (terpy) into the self-assembled Ln III –Pt II system resulted in the one-dimensional [Ln III (terpy)(H 2 O) 2 (NO 3 )][Pt II (CN) 4 ]· n (solvent) (Ln = Eu, Tb) zig-zag chains (Figure 4a) [81,87]. Under UV light excitation of various wavelengths, the EuPt chains exhibits exclusively the sharp emission peaks assigned to Eu III which clearly indicates the efficient dual acceptor–donor intramolecular energy transfer from both terpy ligand and [Pt II (CN) 4 ] 2− ions to 4f metal centre (Figure 4b) [81].…”

“…Thus, only the terpy-to-Tb 3+ energy transfer is efficient while the analogous Pt II -to-Tb 3+ process is partial. It leaves two distinguishable emission sources that can be selectively induced, giving the excitation-dependent visible photoluminescence (Figure 4b) [87]. The crucial role of direct coordination of both terpy and [Pt II (CN) 4 ] 2− ions to the 4f metal centre was precisely investigated for the Eu III –terpy–Pt II system, for which three different crystalline phases, two cyanido-bridged chains, a zig-zag-type [Eu III (terpy)(H 2 O) 2 (NO 3 )][Pt II (CN) 4 ]·MeCN, and a ladder-type [Eu III (terpy)(H 2 O) 3 ] 2 [Pt II (CN) 4 ] 3 ·2H 2 O, along with an ionic salt, [Eu III (terpy)(H 2 O) 2 (CH 3 COO) 2 ] 2 ·{Pt II (CN) 4 }·3H 2 O, were obtained.…”

“…The similar effect was also presented for the Tb III –Pt II systems with terpy and its 4’-chloro-2,2’:6’2”-terpyridine (terpyCl) derivative. The related cyanido-bridged chains, bearing the directly bonded organic ligand, 4f and 5d metal centres, reveal at least partial dual terpy- and Pt II -to-Tb 3+ energy transfers while the ionic salts with non-coordinated tetracyanidoplatinates(II) show the green Tb 3+ emission sensitized only by terpy, and the other coordinated ligands [87]. …”