Synthesis and Properties of a Novel Series of Organometallic Merocyanines Combining the Potent Electron-Donating [(CpFeCO)2(μ-CO)(μ-C=CH−)] Fragment with Tropylium-Type Acceptors

Abstract

The potent electron‐donating group [(CpFeCO)2(µ‐CO)(µ‐C=CH−)] was combined with different tropylium‐based acceptors yielding the push‐pull complexes [(CpFeCO)2(µ‐CO)(µ‐C=CH−CH=A)][BF4] where =A represents [=CH−(η7‐C7H6)Cr(CO)3]+ (5), [={C10H7}]+ (azulenylium) (7) [={C10H4Me2iPr}]+ (guaiazulenylium) (8). Crystal structures of the precursor complexes [(CpFeCO)2(µ‐CO)(µ‐C=CH−CH=CH−C7H7)] (3), [(CpFeCO)2(µ‐CO){µ‐C=CH−CH=CH−(η6‐C7H7)Cr(CO)3}] (4) and the push‐pull derivative 5 are presented. Whereas complexes 3 and 4 demonstrate localised carbon−carbon double and single bonds in the π‐bridge between the diiron moiety and the seven‐membered ring a small but distinct π‐bond delocalisation can be observed in the π‐linker of the cationic derivative 5. From the NMR spectroscopic results a correlation between the 13C NMR shift of the bridging carbon atom µ‐C of the diiron unit and the coupling constant J(1H‐1H) of the β‐ and γ‐protons of the π‐bridge was found. This correlation indicates an increased π‐bond delocalisation throughout the conjugated bridge with respect to the electron‐accepting capability in the order tricarbonyl(η7‐cycloheptatrienylium)chromium < guaiazulenylium < azulenylium implying a predominantly charge‐delocalised form in the case of the azulenylium complex 7. Considerably large first hyperpolarisabilities β were determined for 5 and 8 by means of hyper‐Rayleigh scattering. Based on the two‐level model β0 values were calculated and related to the bond‐length alternation in the π‐linker. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Synthesis and electrochemical studies of organometallic cobalt(III) complexes with substituted benzonitrile chromophores: NMR spectroscopic data as a probe on the second-order non-linear optical properties

“…These results seem to indicate that NMR spectroscopic data might be used to give an insight of the role played by the organometallic fragment on the first hyperpolarizability response of complexes containing the same chromophore. Within the same scope to relate NMR spectroscopic parameters with first hyperpolarizabilities, other authors reported a correlation between 1 H-1 H coupling constants and the first hyperpolarizability of organometallic merocyanines [27]. The linear trend found in this work can be useful to predict first hyperpolarizabilities of other monocyclopentadienylmetal complexes containing p-NCC 6 H 4 NO 2 or p-NC(C 6 H 4 ) 2 NO 2 chromophores if the degree of electronic communication between the corresponding organometallic fragment and nitrile derivatives is known.…”

Conducting Azulene−Thiophene Copolymers with Intact Azulene Units in the Polymer Backbone

“…At zero TFA concentration, the polymer exhibits two strong absorption bands at 238 and 386 nm in the UV region of the spectrum associated with the π-π* transition of the thiophene ring and the azulene moiety, respectively. Upon addition of TFA, a new band at 694 nm was observed which was attributed to the formation of azulenium cation radicals 16,17 (refer to later discussion on the EPR study). In fact, an increase in the TFA concentration (<30%, v/v) and a rise in absorbance in intensity of the band at 694 nm (1.78 eV) are concomitant with a gradual bleaching of the π-π* transition band at 386 nm.…”

Recent advances in the functionalization of azulene through Rh‐, Ir‐, Ru‐, Au‐, Fe‐, Ni‐, and Cu‐catalyzed reactions

“…After filtering the reaction mixture and overlaying the filtrate with diethyl ether, the air‐stable merocyanine salts 195 and 196 were separated (Scheme 71). [ 108 ]…”

“…The hyper‐Rayleigh scattering (HRS) tests were successful in determining the nonlinear optical characteristics of 196 , and the lesser β0 value may be explained by a smaller bond length variation even though the guaiazulenylium cation is a much stronger electron acceptor. [ 108 ]…”

“…After filtering the reaction mixture and overlaying the filtrate with diethyl ether, the air-stable merocyanine salts 195 and 196 were separated (Scheme 71). [108] The reaction of the formyl-substituted μ-vinylidene complex 197 with azulene 1 and guaiazulene 6 was proposed as an alternative synthetic pathway to 195 and 196. In high yields, the isolation of 195 and 196 was achieved by condensation of 197 with an equimolar quantity of azulene or guaiazulene in THF with a substantial excess of HBF 4 198 (Scheme 72).…”