Ferrocene and Azulene - a Promising Combination for NLO Materials
Rudolf Herrmann*, Gabriele Wagner and Cordt Zollfrank
Institut für Organische Chemie und Biochemie der Technischen
Universität München, Lichtenbergstr.4,
D - 85747 Garching (Germany)
Dedicated to Prof. Peter L. Pauson on the occasion of his 70th birthday
Materials exhibiting non-linear optical (NLO) properties are of great interest
for the development of optical devices. They generally contain a donor - acceptor
combination connected by a conjugated bridge. Since both ferrocene (donor) and
azulene (donor: five-membered ring, acceptor: seven-membered ring) derivatives
are known to exhibit NLO properties to some degree
[1 - 8],
we became interested in the potential of molecules containing both groups.
Syntheses
Experimental
Optical Properties of New Compounds
While amine 4 and the alcohols 6 and 7 have optical
properties similar to a superposition of that of the starting materials,
cation 3 (connecting ferrocene and azulene with the five-membered ring)
exhibits a much stronger band at 691 nm (epsilon = 4190),
demonstrating the delocalization of the positive charge.
The alkenes 8 and 9, obtained as a 9:1 mixture,
contain ferrocene, azulene (connected with the seven-membered ring), and
an additional substituent at the double bond. The UV spectrum of 8a (R = H)
shows
absorptions in the visible region (396 nm, epsilon = 8720) not present in the parent compounds
(UV/VIS spectra of cation 3 and alkene 8a in acetone), and a solvatochromic effect of the lowest
energy band (502 nm in acetone, 482 nm in hexane).
Calculations of Second Order Hyperpolarizabilities (beta)
For discussion, here is the e-mail-link: R.Herrmann, TU München
Research group of Priv.Doz. Dr. Rudolf Herrmann, May 25th 1995
