Res. Chem. Intermed.
, Vol. 31, No. 1–3, pp. 25–38 (2005)
Also available online - www.vsppub.com
Photophysical and transition metal ion signaling properties
of some 4-amino-1,8-naphthalimide derivatives
SANDIP BANTHIA, MOLOY SARKAR and ANUNAY SAMANTA
School of Chemistry, University of Hyderabad, Hyderabad 500 046, India
Received 15 March 2004; accepted 10 April 2004
Abstract—Photophysical and transition metal ion signaling behaviour of several 4-amino-1,8-
naphthalimide derivatives in aprotic solvents, tetrahydrofuran and acetonitrile, are reported. The
weakly ﬂuorescent nature of the ﬂuorophore–spacer–receptor systems (1a, 1b) compared to the parent
ﬂuorophore is shown to be due to photoinduced electron transfer (PET) between the terminal moieties
of the systems. PET is found to be more efﬁcient in polar medium. These systems show reasonably
good ‘off–on’ ﬂuorescence signaling in the presence of the transition metal ions. On the other hand,
2, 3a and 3b show unusual absorption and ﬂuorescence behavior in acetonitrile in the presence of
. These spectral changes have been found to be particularly useful for speciﬁc signaling of Cu
in acetonitrile. The present study also reveals that reduction of Cu
in this solvent aided by
the hydrogen atom of the 4-amino group of the ﬂuorophore leads to the observed spectral changes.
Keywords: 4-Amino-1,8-naphthalimide; ﬂuorophore–spacer–receptor system; ﬂuorescence signaling;
transition metal; aprotic solvent; photo-induced electron transfer.
Design and synthesis of chromo- and ﬂuorosensors [1–5] for selective recognition
of biologically important cations, such as Zn
[6–8], are active areas of
contemporary research. Most of the ﬂuorescent sensors reported to date comprise
crown ether, thia-crown ether, aza-crown ether or cryptands as the ionophore.
However, these systems lack selectivity in their signaling behaviour. Fabbrizzi
et al. have reported speciﬁc recognition of Cu
where the sensing action involves
ﬂuorescence quenching [9, 10]. Very recently, a case of ﬂuorescence enhancement
, even in the presence of other metal ions, has been reported . Zheng
et al. have recently developed a ﬂuorescent chemosensor selective for Cu
the ﬂuorescence quenching property of the metal ion .
To whom correspondence should be addressed. E-mail: firstname.lastname@example.org