Terpyridine Zn(II), Ru(III), and Ir(III) Complexes: The Relevant Role of
the Nature of the Metal Ion and of the Ancillary Ligands on the
Second-Order Nonlinear Response of Terpyridines Carrying Electron
Donor or Electron Acceptor Groups
Francesca Tessore,* Dominique Roberto, Renato Ugo, and Maddalena Pizzotti
Dipartimento di Chimica Inorganica, Metallorganica e Analitica dell’UniVersita ` di Milano, Centro
di Eccellenza CIMAINA, Unita ` di Ricerca di Milano dell’INSTM e Istituto di Scienze e Tecnologie
Molecolari del CNR, Via G. Venezian, 21-20133 Milano, Italy
Silvio Quici and Marco Cavazzini
Istituto di Scienze e Tecnologie Molecolari del CNR, Via C. Golgi, 19-20133 Milano, Italy
Silvia Bruni
Dipartimento di Chimica Inorganica, Metallorganica e Analitica dell’UniVersita ` di Milano, Via G.
Venezian, 21-20133 Milano, Italy
Filippo De Angelis
Istituto di Scienze e Tecnologie Molecolari del CNR, c/o Dipartimento di Chimica, UniVersita ` di
Perugia, Via Elce di Sotto 8-06123 Perugia, Italy
Received June 15, 2005
Coordination of 4′-(C
6
H
4
-p-X)-2,2′:6′,2′′-terpyridines [X ) NO
2
, NBu
2
,(E)-CHdCH-C
6
H
4
-p-NBu
2
,(E,E)-(CHdCH)
2
-
C
6
H
4
-p-NMe
2
] to Zn(II), Ru(III), and Ir(III) metal centers induces a significant enhancement of the absolute value of
the second-order nonlinear optical (NLO) response of the terpyridine, measured by means of both electric field
induced second harmonic generation and solvatochromic methods. By varying the nature of the metal center, the
enhanced second-order NLO response shifts from positive to negative. Such a shift is controlled by electronic
charge-transfer transitions, such as metal-to-ligand or ligand-to-metal transitions, in addition to the intraligand charge
transfer. The enhancement generated by coordination is also controlled by the chelation effect and by fine-tuning
of the ancillary ligands.
Introduction
In recent years organometallic and coordination com-
pounds have attracted increasing attention as new chro-
mophores for second-order nonlinear optical (NLO) re-
sponses. In particular, they may offer additional flexibility
by introducing new electronic charge-transfer transitions
between the metal and the ligand, and a response, tunable
by virtue of the nature, oxidation state, and coordination
sphere of the metal center.
1,2
In particular, the effects of
coordination of various push-pull ligands, such as substi-
tuted pyridines,
3a-e,g
bipyridines,
4
and phenanthrolines,
3b,f
have been extensively studied for a series of metal com-
plexes. For instance when these push-pull ligands bear a
NR
2
electron donor substituent, a significant increase was
usually reported upon coordination of
λ
, which is the
projection of the vectorial component of the quadratic hyper-
polarizability tensor along the dipole moment direction,
* E-mail: francesca.tessore@unimi.it.
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J. A., Meyer, T. J., Eds.; Elsevier Pergamon: Oxford, UK, 2004; Vol.
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Properties of Inorganic Compounds; Plenum Press: New York, 1999.
(c) Heck, J.; Dabek, S.; Meyer-Friedrichsen, T.; Wong, H. Coord.
Chem. ReV. 1999, 190-192, 1217-1254.
(2) (a) Le Bozec, H.; Renouard, T. Eur. J. Inorg. Chem. 2000, 229-239.
(b) Di Bella, S. Chem. Soc. ReV. 2001, 30, 355-366.
Inorg. Chem. 2005, 44, 8967-8978
10.1021/ic050975q CCC: $30.25 © 2005 American Chemical Society Inorganic Chemistry, Vol. 44, No. 24, 2005 8967
Published on Web 10/22/2005