Synthesis, characterization and solid-state photoluminescence studies of six alkoxy phenylene ethynylene dinuclear palladium(ii) rods

Abstract

A rare family of six discrete binuclear [PdCl(PEt3)2] phenylene ethynylene rods with alkoxy side chains (methoxy, ethoxy and heptoxy) have been developed, and their solid-state photoluminescence results have been presented and discussed. The shorter bridging ligands are of the general formula H-C≡C-C6H2(R)2-C≡C-H, where R = H, OCH3, OC2H5, and OC7H15, whereas the longer ones are based on H-C≡C-C6H4-C≡C-C6H2(R)2-C≡C-C6H4-C≡C-H, where R = OCH3, OC2H5. These ligands display increasing length in both the main dimension (backbone length) as well as the number of carbons in the side chains (R, alkoxide side chain) that stem from the central phenylene moiety. The X-ray crystal structures of two of the prepared complexes are reported: one corresponds to a shorter rod, 1,4-bis[trans-(PEt3)2ClPd-C≡C]-2,5-diethoxybenzene (6c), while the second one is associated with a longer rod, the binuclear complex 1,4-bis[trans-(PEt3)2ClPd-4-(-C≡C-C6H4-C≡C)]-2,5-diethoxybenzene (7c). All new compounds were characterized by NMR spectroscopy ((1)H, (13)C{(1)H} and (31)P{(1)H}) as well as ESI-MS(TOF), EA, FTIR, UV-Vis, cyclic voltammetry and solid-state photoluminescence. Our work shows the influence of the alkoxy side chains on the electronic structure of the family of binuclear Pd rods by lowering its oxidation potential. In addition to this, the increase of the length of the bridge results in a higher oxidation potential. Solid state photoluminescence results indicate that Pd complexes are characterized by a marked decrease in both the emission intensity and the fluorescence lifetime values as compared to their ligands. This behaviour could be due to some degree of ligand-to-metal charge transfer.

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure–Property Relationships and Applications

“…In a recent work, discrete binuclear [PdCl­(PEt 3 ) 2 ] bridged by shorter and longer phenylene ethynylene rods 187a,b (Chart ) have been reported. Like the previous reports, the complexation with Pd­(II) led to marked decrease in both the emission intensity and the Φ F values compared to their ligands, attributed to LMCT . However, the absorption of the starting ligand and the resulting complex were very similar.…”

“…Like the previous reports, the complexation with Pd(II) led to marked decrease in both the emission intensity and the Φ F values compared to their ligands, attributed to LMCT. 374 However, the absorption of the starting ligand and the resulting complex were very similar. This work also reported the X-ray crystal structure of dinuclear rod 187b, which is the first of its kind (Figure 19b).…”

“…Copyright 2015 Elsevier Ltd. (b) X-ray crystal structures of 187b . Figure reproduced with permission from ref , which is licensed under a Creative Commons Attribution 3.0 Unported License 2015 The Royal Society of Chemistry.…”

Designing Poly(arylene ether sulfone)s with Platinum(II) Acetylide to Regulate Photophysical Properties toward Solid-State Nonlinear Limiters

“…The ultraviolet–visible (UV–vis) absorption spectra depicted in Figure a provide information about the ground-state properties of Fs-Pt-1, Fs-Pt-2, PAES-Pt-1–10%, and PAES-Pt-2–10% in THF, and more specific values are shown in Table . All the complexes showcase intense absorption in the near-ultraviolet region with negligible solvent effects (Figure S6), indicating the presence of localized π–π* transitions originating from the ethynyl aromatic ligands. − The longer conjugation length makes the maximum absorption bands (λ max ) appear to red-shift (Fs-Pt-1 and PAES-Pt-1–10%: ∼342 nm, Fs-Pt-2 and PAES-Pt-2–10%: ∼381 nm) but still ensures prominent optical transparency in most of the visible light region. Also, from 3 to 15% of Pt contents, almost no shift is noticed according to the λ max of the same series of the platinum acetylide monomers and polymers (Figure S7a,b), conforming the negligible proportion effect and ground-state interaction on the polymer chains.…”