Synthesis and Characterization of Redox-Active Mononuclear Fe(κ²-dppe)(η⁵-C₅Me₅)-Terminated π-Conjugated Wires

Abstract

International audienceSeveral new redox-active Fe(κ2-dppe)(η5-C5Me5) arylacetylide complexes featuring pendant ethynyl (Fe(κ2-dppe)(η5-C5Me5)[{C≡C(1,4-C6H4)}nC≡CH] (1b-d; n = 1-3), Fe(κ2-dppe)(η5-C5Me5)[C≡C(1,3-C6H4)C≡CH] (2)) or ethenyl (Fe(κ2-dppe)(η5-C5Me5)[C≡C(1,4-C6H4)CH═CH2] (3)) groups have been synthesized and characterized under their Fe(II) and Fe(III) states. In contrast to the known ethynyl Fe(III) complex [Fe(κ2-dppe)(η5-C5Me5)(C≡CH)][PF6] (1a[PF6]), most of the new Fe(III) derivatives turned out to be kinetically stable in solution. A consistent picture of the electronic structure of the latter complexes in both redox states emerged from experimental data and DFT calculations. This study revealed that beyond the first 1,4-phenylene ring, modification or extension of the carbon-rich linker using (4-phenylene)ethynylene spacers will have only a minor influence on their electronic properties in their ground state, while still maintaining some (weak) electronic interaction along the carbon-rich backbone

Covalent Immobilization of Redox-Active Fe(κ2-dppe)(η5-C5Me5)-Based π-Conjugated Wires on Oxide-Free Hydrogen-Terminated Silicon Surfaces

“…26,27 Comparison of spectra of organoiron-modified porous Si(100) surfaces with that of hydrogen-terminated porous Si(100) evidenced ν CCFe vibration bands characteristic of the immobilized organometallic center at 2054, 2048, and 2046 cm −1 for Si-1b−d, respectively (Figure 3a), which are consistent with the values and trends observed for the complexes (Figure 3b). 18 In the ν CC stretching vibration region (i.e., between 1600 and 1400 cm −1 ), the presence of a band at 1589 ± 2 cm −1 in the spectrum of Si-1b−d can be ascribed to the 1,4-phenylene spacer, while the CHCH unit bound to the silicon surface at 1570 cm −1 are not always plainly detected but show up as a shoulder to the previous peaks. 28 This is somewhat comparable to the value near 1620 cm −1 attributed to the ν CHCH 2 mode for 3.…”

“…Toward this aim, using a photochemical grafting protocol previously communicated, 17 we have now isolated the corresponding monolayers on Si−H (Chart 1), starting from a series of mononuclear Fe(κ 2 -dppe)(η 5 -C 5 Me 5 ){[CC(1,4-C 6 H 4 )] n CCH} (1a−d; n = 0−3), Fe(κ 2 -dppe)(η 5 -C 5 Me 5 )[CC(1,3-C 6 H 4 )CCH] (2), and Fe(κ 2 -dppe)(η 5 -C 5 Me 5 )[CC(1,4-C 6 H 4 )CHCH 2 ] (3) complexes previously synthesized. 18 From such functional interfaces, electrochemical studies on 1a−d-modified Si−H surfaces (Si-1a−d) should reveal the incidence of the phenylethynyl spacer extension on the interfacial electrontransfer characteristics, while comparison among Si-1b, Si-2, and Si-3 should bring complementary information on the topological and structural features which are determining for this property with this kind of unsaturated spacer.…”

“…The synthesis of the organometallic Fe(II) precursors 1b−d, 2, and 3 has been previously reported. 18 17 from the photochemical grafting reaction initially developed by Chidsey and co-workers for phenylacetylene or styrene. 21,22 Attempts at thermal grafting (100°C overnight) were also performed but were found to yield redox-active films with a lower surface coverage and a more pronounced oxidation of the underlying silicon.…”

Validation of a computational protocol to simulate near IR phosphorescence spectra for Ru(II) and Ir(III) metal complexes

“…Therefore, computationally oriented chemists can provide crucial information on these molecules, especially thanks to the very recent developments in this area [13][14][15][16]. Furthermore, Density Functional Theory (DFT) and its TimeDependent extension (TD-DFT) are increasingly used to get electronic and vibrational information from small-to large-size systems thanks to the strong improvements in hardware and software [17][18][19][20][21][22][23]. Among all its possibilities, the DFT approach can be used for the prediction or confirmation of compounds [21,24,25] and the explanation of the luminescent and spectroscopic properties of multi-scale systems [13, [26][27][28][29][30][31][32][33].…”

Vibronic coupling to simulate the phosphorescence spectra of Ir(III)-based OLED systems: TD-DFT results meet experimental data

“…[18][19][20][21][22][23] Moreover, Density Functional Theory (DFT) and its time dependent extension (TD-DFT) are now routinely used to get both electronic and vibrational information from small organic to large-size organometallic and transition metal complexes systems. [10,[24][25][26][27][28][29][30] Indeed, DFT calculations are now accurate enough to predict or confirm the stability or existence of compounds, and they can also explain the luminescent and/or spectroscopic properties of complex systems. [31][32][33][34][35][36][37][38][39][40] In the field of spectroscopy calculations, Vlcek Jr. and Zális among other authors, have shown how DFT and TD-DFT are useful tools to study d 6 metal complexes.…”