Compromise between conjugation length and charge-transfer in nonlinear optical η5-monocyclopentadienyliron(II) complexes with substituted oligo-thiophene nitrile ligands: Synthesis, electrochemical studies and first hyperpolarizabilities

Benzo[c]thiophene Chromophores Linked to Cationic Fe and Ru Derivatives for NLO Materials: Synthesis Characterization and Quadratic Hyperpolarizabilities

“…The resonances are in the range usually observed for monocationic ruthenium(II) and iron(II) complexes. The same general behaviour of the NMRresonanceshasbeenobservedpreviouslyinrelatedoligothiophene iron(II) [14] and ruthenium(II), [13] and 1,2-di(2-thienyl)ethene iron(II) and ruthenium(II) [12] complexes. The optical absorption spectra of the complexes at concentrations of 1.0 ϫ 10 -5 m were recorded in chloroform and DMF.…”

“…[46] Commercial reagents were used without further purification. Organometallic starting materials were prepared following methods described in the literature: [Fe(η 5 -C 5 H 5 )-(dppe)I], [14] [Ru(η 5 [47] Compounds 1-3 were prepared following published procedures [35] with some modifications (see details below). 5-(3-Thiophen-2-yl-benzo[c]thiophenyl)thiophene-2-carbaldehyde (5) was prepared following a published procedure [48] but with a different purification method (see details below).…”

“…The magnitude of this π-back-donation is thus higher for the iron(II) compound, as expected considering the better π-donating ability of the iron(II) moiety. The benzo[c]thiophene derivatives described here show more effective π-back-donation than those possessing terthiophene units with an acceptor nitro end-group in related oligothiophene iron(II) [14] and ruthenium(II) [13] complexes. Moreover, less effective π-back-donation was found in comparison with parent 1,2-di(2-thienyl)ethene iron(II) and ruthenium(II) [12] complexes, which possess one vinylidene unit between the two thiophene rings.…”

“…Among the organometallic compounds presenting this structural feature, our group and others have carried out systematic studies on η 5 -monocyclopentadienylmetal complexes with benzene or oligothiophene conjugated chains coordinated to the metal centres through nitrile or acetylide linkages. [8,[12][13][14][15][16][17][18] In particular, very efficient NLO responses were found when strong electron donors such as iron and ruthenium organometallic moieties were coupled with strong electron acceptors like NO 2 .…”

Synthesis of organometallic Ru(II) and Fe(II) complexes containing fused rings hemi-helical ligands as chromophores. Evaluation of non-linear optical properties by HRS

“…In particular, structures presenting the metal centre and the chromophore in the same plane, have been found of potential interest for second-order optical nonlinearities, due to the charge delocalization through a d metal -p * ligand interaction. This is widely illustrated in the literature by the families of g 5 -monocyclopentadienyl iron and ruthenium molecular materials presenting p-nitrobenzonitriles [7][8][9][10], p-nitrobenzoacetylides [11][12][13], nitrothienylacetylides [14] and thiophene derivatives [15]. Although the first molecular hyperpolarizability of purely organic push-pull molecules increases strongly with the length of the conjugated chain [16,17], this is not the case for the benzoderivatives, due to the torsion angle between the rings.…”