Chapter 12
119Sn Mossbauer Spectroscopy Studies on the
Interaction of Organotin(lV) Salts and Complexes
with Biological Systems and Molecules
R. Barbieri· 1. Pellerito· G. Ruisi . A. Silvestri· A. Barbieri-Paulsen· G. Barone
S. Posante . M. Rossi
12.1
Introduction
Organotin(IV) compounds are widely spread out in the environment (Blunden and
Chapman 1986), owing to their industrial uses (Blunden et al. 1985; Evans 1998). Interacting with living organisms, effects are provoked on biological systems and functions
(Thayer 1984; Arakawa 1998; Smith 1998).
119Sn Mossbauer spectroscopy (whose principles are sketched in a recent review by
Barbieri et al. 1998) has been employed in a number of studies on bonding and structure of organotins in biological systems, as well as bound to biological molecules. The
speciation of triorganotins spiked to estuarine sediments (see Section 12.2) was effected
by comparison of the spectra of pure triorganotins, in the solid state, with spectra of
spiked samples, obtaining information about the nature of the tin derivative in a given
sediment. In fact, Mossbauer spectroscopy cannot be employed as a microanalytical
technique for the determination of trace elements (Barbieri et al. 1998); organotins in
relatively low amounts could be investigated employing Rn 119snX4_n derivatives, synthesized from 119Sn metal samples. In the case of organotin(IV) complexes with biological molecules, possibly with known stoichiometry, the structure and bonding of the
tin environment are generally determined at a high degree of certainty by the pointcharge model treatment of the parameter nuclear quadrupole splitting, t.E (Barbieri
et al. 1998, and refs. therein). The eventual degradation to inorganic derivatives, and
in a special way the formation of Sn(II) compounds, is detected by the magnitude of
the parameter isomer shift, (j (Barbieri et al. 1998). Structural information is also extracted from (j / QSn correlations, QSn being the partial charge on tin atoms (Barbieri
and Silvestri 1984).
In the present review, besides the speciation studies above mentioned, 119Sn Mossbauer determinations of structure and bonding are reported and discussed for organotins coordinated to biological system components, to hemoglobin and to nucleic acids. Particular emphasis is given to unpublished work on the interaction with DNA,
and tin bonding and structures in the obtained DNA condensates, by mono-organotin
derivatives as well as by RnSn(IV) complexes; systems RnSn(IV)-aminoacid-DNA are
reported and discussed in the context of protein-nucleic acids interactions. [Annotation: It seems worthwhile to note that the actual scientific activity at the Department
of Inorganic Chemistry, University of Palermo, concerning research on organotin
chemistry (extended to environmental interactions) as well as Mossbauer spectroscopy investigations, originates from studies started at the University of Padua, as far
as Italian sources are concerned. In fact, pioneering work on organometals was effected
by G. Semerano and 1. Riccoboni around 1935-1941 at the Institute of Physical Chem-
119Sn Mossbauer Spectroscopy Studies on the
Interaction of Organotin(lV) Salts and Complexes
with Biological Systems and Molecules
R. Barbieri· 1. Pellerito· G. Ruisi . A. Silvestri· A. Barbieri-Paulsen· G. Barone
S. Posante . M. Rossi
12.1
Introduction
Organotin(IV) compounds are widely spread out in the environment (Blunden and
Chapman 1986), owing to their industrial uses (Blunden et al. 1985; Evans 1998). Interacting with living organisms, effects are provoked on biological systems and functions
(Thayer 1984; Arakawa 1998; Smith 1998).
119Sn Mossbauer spectroscopy (whose principles are sketched in a recent review by
Barbieri et al. 1998) has been employed in a number of studies on bonding and structure of organotins in biological systems, as well as bound to biological molecules. The
speciation of triorganotins spiked to estuarine sediments (see Section 12.2) was effected
by comparison of the spectra of pure triorganotins, in the solid state, with spectra of
spiked samples, obtaining information about the nature of the tin derivative in a given
sediment. In fact, Mossbauer spectroscopy cannot be employed as a microanalytical
technique for the determination of trace elements (Barbieri et al. 1998); organotins in
relatively low amounts could be investigated employing Rn 119snX4_n derivatives, synthesized from 119Sn metal samples. In the case of organotin(IV) complexes with biological molecules, possibly with known stoichiometry, the structure and bonding of the
tin environment are generally determined at a high degree of certainty by the pointcharge model treatment of the parameter nuclear quadrupole splitting, t.E (Barbieri
et al. 1998, and refs. therein). The eventual degradation to inorganic derivatives, and
in a special way the formation of Sn(II) compounds, is detected by the magnitude of
the parameter isomer shift, (j (Barbieri et al. 1998). Structural information is also extracted from (j / QSn correlations, QSn being the partial charge on tin atoms (Barbieri
and Silvestri 1984).
In the present review, besides the speciation studies above mentioned, 119Sn Mossbauer determinations of structure and bonding are reported and discussed for organotins coordinated to biological system components, to hemoglobin and to nucleic acids. Particular emphasis is given to unpublished work on the interaction with DNA,
and tin bonding and structures in the obtained DNA condensates, by mono-organotin
derivatives as well as by RnSn(IV) complexes; systems RnSn(IV)-aminoacid-DNA are
reported and discussed in the context of protein-nucleic acids interactions. [Annotation: It seems worthwhile to note that the actual scientific activity at the Department
of Inorganic Chemistry, University of Palermo, concerning research on organotin
chemistry (extended to environmental interactions) as well as Mossbauer spectroscopy investigations, originates from studies started at the University of Padua, as far
as Italian sources are concerned. In fact, pioneering work on organometals was effected
by G. Semerano and 1. Riccoboni around 1935-1941 at the Institute of Physical Chem-