Donor/acceptor organotriiron(II) hydrazone chromophores: structural, spectroscopic and electrochemical properties

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

“…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.…”

“…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].…”

Dipolar Organoiron Pyranylideneacetaldehyde Hydrazone Complexes: Synthesis, Characterization, Crystal Structure, Linear and Nonlinear Optical Properties

“…Ϸ 10 Hz) assigned to the deshielded imine proton, and the low-field position (δ = 9.21-9.48 ppm) of the acidic benzylic N-H signal appear in their expected regions. [13,14] On the other hand, the vinylic 3-H resonance of the methylenepyran core (see Figure 1 for labelling scheme), which is common to the three compounds under investigation, appears as a doublet ( 4 J H,H = 2.0 Hz) for 4 and as a singlet for 5 and 6, at δ = 6.24, 6.38, and 6.85, respectively. Like the 3-H signal, 5-H also appears as a singlet, which strongly indicates that compound 6 is isolated as a single isomer about the C-2=C(exocyclic) double bond, even though the starting pyranic aldehyde 3 is a mixture of (Z) and (E) isomers.…”

“…[7] On the other hand, the cationic isolobal electron-acceptor counterparts of ferrocene, namely the robust mixed-sandwich derivatives [CpFe(η 6 -arene)] + , [8] have also been the subject of intense investigations within the domains of arene functionalization, [9] electron transfer and redox processes, [10] photochemistry, [11] and, in one case, as an organometallic chromophore to achieve second-order NLO responses. [12] Along this line, some of us have thoroughly investigated organometallic dipolar chromophores in which the electron-withdrawing cationic organometallic fragment [CpFe(η 6 -arene)] + (A) is connected to a potent donating organic [13] or ferrocenyl [14] subunit (D) by an asymmetric -NR-N=CR-(R = H, Me) hydrazone conjugated bridge (π), and have shown that in such D-π-A-type systems an effective electron delocalization or electronic interaction between the electron-donating and -accepting termini takes place through the entire hydrazone skeleton. Others of us have recently reported on donor-acceptor pentacarbonylmetal methylenepyran Fischer-type methoxycarbene complexes (metal = Cr, W).…”