Linear and Third-Order Nonlinear Optical Properties of Fe(η⁵-C₅Me₅)(κ²-dppe)- and trans-Ru(κ²-dppe)₂-Alkynyl Complexes Containing 2-Fluorenyl End Groups

Abstract

The synthesis and characterization of a set of redox-active iron and ruthenium alkynyl complexes of general formula [[M]Cl (1-p) {C≡CC 6 H 5-m (C≡CFlu) m } (1+p) ][PF 6 ] n are reported (n = 0-1; m = 1-2; [M] = [Fe(η 5-C 5 Me 5)(κ 2-dppe)] and p = 1 or [M] = [trans-Ru(κ 2-dppe) 2 ] and p = 0-1). The linear and third-order nonlinear optical properties of these new organometallic complexes featuring phenylalkynyl ligands functionalized by 2-fluorenyl (Flu) groups were studied in their stable redox states. Their first electronic transitions are assigned with the help of DFT calculations. We show here that these compounds possess significant third-order NLO responses in the near-IR range for molecules of their size. In particular, the remarkably large 2PA activities of the new Ru(II) compounds in the 600-800 nm range (Z-scan) make them attractive nonlinear chromophores. Structure-property studies emphasize the importance of para-vs. meta-connection of the 2-fluorenylethynyl units on the phenylalkynyl core, and also reveal that upon progressing from mono-to bis-alkynyl complexes, a further increase of the 2PA cross-section can be obtained while maintaining linear transparency in the visible range.

Triarylisocyanurate‐Based Fluorescent Two‐Photon Absorbers

“…For instance, cross‐sections above 400 GM were found for the known isocyanurate derivatives 21 and 22 (Scheme ) . However, the metal centers in these isocyanurates strongly quench the emission of the appended organic core and 21 or 22 are essentially non‐luminescent at ambient temperatures . In contrast to these organometallic derivatives, the purely organic cyclotrimers presently reported are strongly fluorescent, allowing envisioning practical applications such as fluorescence imaging for these two‐photon absorbers.…”

Fluorenylporphyrins functionalized by electrochromic ruthenium units as redox-triggered fluorescence switches

“…A similar band is found at 373 nm in 4. 13 The fluorescence spectra for 2 and 3 are similar in toluene with two Q bands at ca. 659 and 724 nm for 2' (Figures S5-S6).…”

“…Such bands are characteristic of the fluorenylethynylruthenium moiety on oxidation. 13,14 Thus, the absorption spectra of 2 n+ (n = 0, 1) is merely the sum of those of 3 and 4 n+ in each redox state (ESI; Figures S10a-b). A similar statement can be made for the spectrum of 1 n+ when compared to those of 6 and 5 n+ ( Figures S11a-b), in line with a weak electronic coupling between the organoruthenium endgroup and the porphyrin ring in both dyads, regardless of its oxidation state.…”

“…Finally, these results will be discussed and rationalized in the light of the available data from A-C and from isoelectronic Fe(II) and Ru(II) alkynyl complexes. 13,14,15 As shown in Scheme 1, the desired organometallic compound 2 can be synthesized from porphyrin 3 16 6 ] in good yield. 17 The reaction mixture was stirred at room temperature and its progress was followed by 31…”

Impact of the Subunit Arrangement on the Nonlinear Absorption Properties of Organometallic Complexes with Ruthenium(II) σ-Acetylide and Benzothiadiazole as Building Units §

“…The σ (2) values of these ruthenium complexes are moderately large: 1700 GM for Ru-2 and 280 GM for Ru-1, even though they are somehow lower than those of recently reported Ru(II) alkynyl complexes [25,26]. Interestingly, the dinuclear complex Ru-2 showed a significant enhancement (~6 times) of σ (2) with respect to the mononuclear complex Ru-1, though the magnitudes of the OPA spectra were almost the same.…”