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. 2017 Nov 1:849-#008211850:306-314.
doi: 10.1016/j.jorganchem.2017.03.026. Epub 2017 Mar 16.

Synthesis, structure, photophysical and electrochemical properties of Ru(TFA)(CO)(PPh3)2(L) (L=2-phenylpyridine, 2- p-tolylpyridine) and Ru(CO)(PPhMe2)2(L)(L') (L= TFA, H) (L'= bipyridine, L'= 4,4'-dimethylbipyridine) relationships between ancillary ligand structure and luminescent properties

Shyam Pohkrel  1 , Dan Decato  1 , Edward Rosenberg  1 , J B Alexander Ross  1 , Michelle Terwilliger  1
Affiliations

Synthesis, structure, photophysical and electrochemical properties of Ru(TFA)(CO)(PPh3)2(L) (L=2-phenylpyridine, 2- p-tolylpyridine) and Ru(CO)(PPhMe2)2(L)(L') (L= TFA, H) (L'= bipyridine, L'= 4,4'-dimethylbipyridine) relationships between ancillary ligand structure and luminescent properties

Shyam Pohkrel et al. J Organomet Chem. .

Abstract

The synthesis, structure and photophysical properties of the complexes [Ru[(CO)(TFA) (PPh3)2(L)] [(L = ppy = 2-phenylpyridine, (1a); L = 2-(p-tolyl)pyridine] (1b), are reported. The complexes were characterized by UV-VIS, IR and NMR and by single-crystal X-ray diffraction techniques. We also report the synthesis, structure and photophysical properties of [Ru(CO)(L)(PPhMe2)2(L')]+[PF6]- [L' = bipyridine, L = TFA, (3a); L = H, (3b) and L = H, L' = 4,4'-dimethlyl bipyridine (3c)]. These compounds were characterized by UV-VIS, IR and NMR techniques and by a single crystal X-ray diffraction in the case of 3a. The solid state structure of [Ru(Me2PhP)2(CO)2(TFA)2 (2) which is the starting material for the synthesis 3a-3c is also reported to verify the trans relationship of the less bulky PPhMe2 and for comparison with the previously reported PPh3 analogs. The purpose of this study was to determine the impact, if any, of replacing bpy with ppy in the case of 1a and alkylation of the benzene ring in the case of 1b on the photophysical and electrochemical properties compared to related Ru(bpy) complexes. In contrast to the bpy analogs 1a and 1b showed reversible 1e- oxidations and blue-shifted MLCT absorptions. In the case of 3a-3c we were interested in the effect on the photophysical properties of substituting PPh3 with the less bulky but more electron donating PPhMe2. There were only minor changes in the photophysical and electrochemical properties relative to the previously reported PPh3 analogs.

Keywords: 2-Phenyl pyridine; Bipyridine; Electrochemistry; Phosphine ligands; Photophysical properties; Ru complexes.

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Figures

Fig. 1.
Fig. 1.
Solid-state structure of 1a showing the 50% probability ellipsoids. All hydrogen atoms have been omitted for clarity. Ru(1)-P(1) = 2.3758(3), Ru(1)-P(2) = 2.4108(3), Ru(1)-O(2) = 2.1957(9), Ru(1)-N(1) = 2.1528(11), Ru(1)-C(1) = 2.0432(13), Ru(1)-C(14) = 1.8457(13) Å; P(1)-Ru(1)-P(2) = 178.807(12), O(2)-Ru(1)-P(1) = 87.24(3), O(2)-Ru(1)-P(2) = 93.95(3), N(1)-Ru-P(1) = 92.35(3), C(14)-Ru(1)-C(1) = 90.90(6), C(6)-C(1)-Ru(1) = 114.93(9)°.
Fig. 2.
Fig. 2.
Solid-state structure of 1b showing the 50% probability ellipsoids. All hydrogen atoms have been omitted for clarity. Ru(1)-P(1) = 2.375(6), Ru(1)-P(2) = 2.4200(6), Ru(1)-O(2) = 2.2026(16), Ru(1)-N(1) = 2.1541(18), Ru(1)-C(2) = 2.036(2), Ru(1)-C(1) = 1.848(2) Å; P(1)-Ru(1)-P(2) = 177.37(2), O(2)-Ru(1)-P(1) = 88.14(4), O(2)-Ru(1)-P(2) = 94.50(4), N(1)-Ru-P(1) = 93.04(5), C(1)-Ru(1)-C(2) = 90.67(9), C(7)-C(2)-Ru(1) = 115.09(16)°.
Fig. 3.
Fig. 3.
Methyl region of complex 2 (left); methyl region of complex 3a (right).
Fig. 4.
Fig. 4.
Solid-state structure of 2 showing the 50% probability ellipsoids. All hydrogen atoms have been omitted for clarity. Ru(1)-P(1) = 2.3810(8), Ru(1)-P(2) = 2.3790(8), Ru(1)-O(3) = 2.103(2), Ru(1)-O(5) = 2.0968(19), Ru(1)-C(1) = 1.862(3), Ru(1)-C(2) = 1.875(3) Å, P(1)-Ru(1)-P(2) = 176.30(3), O(3)-Ru(1)-P(1) = 87.60(6), O(3)-Ru(1)-P(2) = 92.17(6), O(3)-Ru(1)-O(5) = 79.64(8)°
Fig. 5.
Fig. 5.
Solid-state structure of (3a) showing the 50% probability ellipsoids. All hydrogen atoms and the PF6 anion have been omitted for clarity. Ru(1)-P(1) = 2.3755(12), Ru(1)-P(2) = 2.3785(12), Ru(1)-O(2) = 2.089(3), Ru(1)-N(1) = 2.053(4), Ru(2)-N(2) = 2.102(4), Ru(1)-C(1) = 1.868(5) Å. P(1)-Ru(1)-P(2) = 175.49(6), O(2)-Ru(1)-N(2) = 89.71(14), C(1)-Ru(1)-N(1) = 95.22(18), N(1)-Ru(1)-N(2) = 78.61(15), C(1)-Ru(1)-O(2) = 96.46(18)°.
Fig. 6.
Fig. 6.
Complex 3a showing the possible π-π stacking of the phosphine phenyl and the bpy aromatic rings.
Fig. 7.
Fig. 7.
CV of a 1.0 mM solution of 1a and 1b in CH2Cl2 containing 0.10 M[NBu4][PF6], at a glassy carbon working electrode.
Fig. 8.
Fig. 8.
CV of a 1.0 mM solution of 3b and 3c in CH2Cl2 containing 0.10 M[NBu4][PF6], at a glassy carbon working electrode.
Fig. 9.
Fig. 9.
Emission (left) and excitation (right) spectra for 3c measured in CH2Cl2.
Scheme 2.
Scheme 2.
Synthesis of 3a-3c starting with 2.
Scheme 1.
Scheme 1.
Synthesis of 1a and 1b.
See this image and copyright information in PMC

References

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