Preparation, characterization and electrochemical and X-ray structural studies of new conjugated 1,1′-ferrocenediyl-ended [CpFe-arylhydrazone]⁺salts

Pentamethylcyclopentadienyl organoiron(II) hydrazone complexes: Synthesis, spectroscopic characterization, and second-order nonlinear optical properties. X-ray crystal structure of

“…From deconvolutions of the spectra with Gaussian curves, these two CT transitions give rise to two to four absorption bands ( Table 3). The data of Table 3 indicate that linear optical properties (i.e., energies and intensities of the absorption bands corresponding to the above-mentioned CT transitions) of 3-6 are in agreement with those reported for other D-p-A systems having the [CpFe(g 6 -arene)] + fragment as electron acceptor linked to an organic or organometallic electron-donating group [13][14][15][16][17][18][19]21]. The broadening of the low-energy band is probably the result of the overlap of broad d-d visible bands of the cationic sandwich fragment [9,45].…”

“…As expected from previous work [13][14][15][16][17][18], both the mono-and binuclear organoiron hydrazones 4 and 5 are stereoselectively formed as the sterically less hindered trans-isomer (about the N@C double bond) as indicated by the unique set of signals in their 1 H and 13 C NMR spectra (see Section 4). The sandwich moiety [Cp * Fe(g 6 -C 6 H 5 -)] + is clearly identified by the characteristic sharp singlet and the upfield multiplet of the Cp * and phenyl proton resonances observed at d ca.…”

“…For both complexes, this latter resonance splits into two peaks separated by 0.1 ppm. This could result from a possible equilibrium between a g 6 -aminoarene and a g 5 -iminocyclohexadienyl coordination modes to the Cp * Fe + moiety, as supported by theoretical work [11] and previous solid-state studies [13][14][15][16][17][18]30]. In compound 4, the carbon atoms of the coordinated C 6 -ring are upfield shifted relative to those of the free mesityl ring.…”

“…The lowering of the oxidation potentials of 3-6 thus, the observation of the waves, results from the permethylation of the cyclopentadienyl ring. Such an oxidation wave has never been observed for any analogous organometallic hydrazones in the unsubstituted Cp series [13][14][15][16][17][18]. DFT calculations have shown that the HOMO of a complexed aniline has a large contribution from the HOMO of the free amine [11].…”

“…In the last few years, we have been interested in monoand dinuclear dipolar hydrazone D-p-A type organometallic chromophores, in which the electron-withdrawing cationic organometallic fragment [CpFe(g 6 -arene)] + (A) is connected to a potent donating organic [13][14][15] or ferrocenyl [16][17][18] subunits (D) by the asymmetric -NR-N@CR-(R = H, Me) hydrazone conjugated bridge (p), and shown that in such D-p-A type systems an electronic cooperativity between the electron-donating and electronaccepting termini takes place through the entire hydrazone skeleton. Very recently, we used the powerful electronwithdrawing ability of this cationic mixed sandwich to prepare dipolar organometallic chromophores to achieve second-order nonlinear optical (NLO) responses [19].…”