Synthesis, Structures,
and Photophysical Properties
of Ruthenium(II) Quinolinolato Complexes
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Abstract
Reaction of [Ru<sup>II</sup>(PR<sub>3</sub>)<sub>3</sub>Cl<sub>2</sub>] with 2-methyl<b>-</b>8-quinolinolate (MeQ)
in the
presence of Et<sub>3</sub>N in MeOH produced the neutral carbonyl
hydrido complexes [Ru<sup>II</sup>(MeQ)(PR<sub>3</sub>)<sub>2</sub>(CO)(H)] (R = Ph (<b>1</b>), MeC<sub>6</sub>H<sub>4</sub> (<b>2</b>), MeOC<sub>6</sub>H<sub>4</sub> (<b>3</b>)). An analogous
reaction occurs between [Ru<sup>II</sup>(PPh<sub>3</sub>)<sub>3</sub>Cl<sub>2</sub>] and MeQH in ethanol to give [Ru<sup>II</sup>(MeQ)(PPh<sub>3</sub>)<sub>2</sub>(CO)(CH<sub>3</sub>)] (<b>4</b>). The carbonyl,
hydride, and methyl ligands of these complexes are most likely derived
from the decarbonylation of ROH. Reaction of [Ru<sup>II</sup>(PPh<sub>3</sub>)<sub>3</sub>(CO)(H)<sub>2</sub>] with 5-substituted quinolinolato
ligands (XQ, X = H, Cl, Ph) produced the neutral complexes [Ru<sup>II</sup>(XQ)(PPh<sub>3</sub>)<sub>2</sub>(CO)(H)] (XQ = Q (<b>5</b>), ClQ (<b>6</b>), PhQ (<b>7</b>)). Treatment
of <b>1</b> and <b>5</b>–<b>7</b> with excess
KCN in MeOH following by metathesis with PPh<sub>4</sub>Cl afforded
PPh<sub>4</sub><sup>+</sup> salts of the anionic carbonyl dicyano
complexes [Ru<sup>II</sup>(XQ)(CO)(CN)<sub>2</sub>(PPh<sub>3</sub>)]<sup>−</sup> (XQ = MeQ (<b>8</b>), Q (<b>9</b>) ClQ (<b>10</b>), PhQ (<b>11</b>)). Under similar conditions,
reaction of <b>1</b> with excess CyNC in the presence of NH<sub>4</sub>PF<sub>6</sub> afforded [Ru<sup>II</sup>(MeQ)(CyNC)<sub>2</sub>(CO)(PPh<sub>3</sub>)]<sup>+</sup> (<b>12</b>). All complexes
have been characterized by IR, ESI/MS, <sup>1</sup>H NMR and elemental
analysis. The crystal structures of complexes <b>3</b>, <b>4</b>, <b>8</b>, and <b>12</b> have been determined
by X-ray crystallography. The UV and emission spectra of these complexes
have also been investigated. All complexes exhibit short-lived quinolinolate-based
LC fluorescence in solution at room temperature and dual emissions
derived from LC fluorescence and phosphorescence at 77 K glassy medium.
These emissions are relatively insensitive to the nature of the ancillary
ligands but are readily tunable by varying the substituents on the
quinolinolato ligand
