CHAPTER 12 • 119Sn Mossbauer Spectroscopy Studies: Organotin(lV) Salts and Complexes
233
Table 12.2. 1195n Mossbauer parameters of DNA condensates (gels) formed by interaction with mono-,
di- and triorganotin(IV) moieties
No. Compound or system
a
t
AE'
rb
rb
Reference
1
2
(mms- 1 )
(mms- I )
(mms- I )
(mms- I )
MeSnCll(EtOH)n + DNA, 0.56
2.19
0.91
0.90
Posante 1996
r = 0.33
2
id., r= 0.5
0.56
2.25
0.83
0.80
3
id.,r= 1.0
0.56
2.17
0.86
0.72
4
id., r = 0.2-1.2c
0.56 ±0.01
2.17 ±0.04 0.85 ±0.07 0.75 ±0.05
5
Me 2 SnCI 2 (EtOH)n + DNA, 1.26
4.39
0.90
0.79
Barbieri and
r= 0.4
Silvestri 1991
6
id.,r= 1.0
1.33
4.44
0.91
0.91
7
Et 2 SnCI 2 (EtOH)n + DNA,
1.39
4.49
0.89
0.77
Barbieri et al.
r=0.6
1992
8
id.,r= 1.0
1.43
4.40
0.74
0.99
9
MelSnCI(EtOH)n + DNA,
1.31
3.77
0.89
0.82
r=2.4
10
EtjSnCI(EtOH)n + DNA,
1.49
3.86
0.85
0.88
r= 1.0; 1.2
11
id., r= 2.4
1.47
3.83
0.86
0.82
12
MejSn(Hp); + DNA;
1.32
3.80
0.89
0.78
aq. sol., r = 1.20-1.56
13
id., pellet, r = 2.4
1.38
3.84
0.93
0.75
a No.1-II, 13: DNA condensed phases obtained by addition to aqueous (buffered) DNA of: 1-11,
ethanol solutions of organotin chlorides; 73, MelSn(lV) in Hp at acid pH; Mossbauer spectra were
taken on the gelled phases, separated by centrifugation and frozen to 77.3 K. r = [Sn]! [DNA monomer] (DNA monomer = mononucleotide unit, average MW being 315 in calf thymus (native) DNA).
No. 12, aqueous solution frozen at 77.3 K.
b 8= isomer shih with respect to RT CaSnO l or BaSnOj ; AE = nuclear quadrupole splitting; r= full
width at half height of the resonant peaks. Spectra were taken at 77.3 K (liquid N2 temperature)
unless otherwise stated.
c Average data from 27 spectra in the r range indicated, with standard error.
ing to tin by two adjacent phospho diester groups of the DNA chain, and by a phosphodiester adjacent to Sn in the toroidal (Bloomfield 1996) DNA condensate, thus originating the apparent polymeric nature of tin bonding environment (Posante 1996).
Systems Alk 2 SnCI2(EtOH)n + DNA (Alk = Me, Et, No. 5-8, Table 12.2), appear to consist of species Alk2Sn(DNA monomerh, according to molecular dynamics studies on
lyophilized condensates (Barbieri et a1.1992; Barbieri et a1.1995; Posante 1996). Tin environment in gelled and lyophilized systems would be of trans-R2 octahedral type, such
as in Fig. 12.1b. In freeze-dried specimens, two coordination sites of type 12.1b would
occur for each system, according to the fitting of each experimental spectrum with
two symmetric doublets: Me2Sn(DNA monomerh, Mexp = 4.44 mm S-I, CSnC = 180°,
a~d LlEexp = 3.52 mm S-I, CSnC = 143\Et2Sn(DNA monomer}z, LlEexp = 4.35 mm S-I,
CSnC = 180
0
,andMexp = 3.56 mm s-I,CSnC = 145°; angles are estimated by point-charge
233
Table 12.2. 1195n Mossbauer parameters of DNA condensates (gels) formed by interaction with mono-,
di- and triorganotin(IV) moieties
No. Compound or system
a
t
AE'
rb
rb
Reference
1
2
(mms- 1 )
(mms- I )
(mms- I )
(mms- I )
MeSnCll(EtOH)n + DNA, 0.56
2.19
0.91
0.90
Posante 1996
r = 0.33
2
id., r= 0.5
0.56
2.25
0.83
0.80
3
id.,r= 1.0
0.56
2.17
0.86
0.72
4
id., r = 0.2-1.2c
0.56 ±0.01
2.17 ±0.04 0.85 ±0.07 0.75 ±0.05
5
Me 2 SnCI 2 (EtOH)n + DNA, 1.26
4.39
0.90
0.79
Barbieri and
r= 0.4
Silvestri 1991
6
id.,r= 1.0
1.33
4.44
0.91
0.91
7
Et 2 SnCI 2 (EtOH)n + DNA,
1.39
4.49
0.89
0.77
Barbieri et al.
r=0.6
1992
8
id.,r= 1.0
1.43
4.40
0.74
0.99
9
MelSnCI(EtOH)n + DNA,
1.31
3.77
0.89
0.82
r=2.4
10
EtjSnCI(EtOH)n + DNA,
1.49
3.86
0.85
0.88
r= 1.0; 1.2
11
id., r= 2.4
1.47
3.83
0.86
0.82
12
MejSn(Hp); + DNA;
1.32
3.80
0.89
0.78
aq. sol., r = 1.20-1.56
13
id., pellet, r = 2.4
1.38
3.84
0.93
0.75
a No.1-II, 13: DNA condensed phases obtained by addition to aqueous (buffered) DNA of: 1-11,
ethanol solutions of organotin chlorides; 73, MelSn(lV) in Hp at acid pH; Mossbauer spectra were
taken on the gelled phases, separated by centrifugation and frozen to 77.3 K. r = [Sn]! [DNA monomer] (DNA monomer = mononucleotide unit, average MW being 315 in calf thymus (native) DNA).
No. 12, aqueous solution frozen at 77.3 K.
b 8= isomer shih with respect to RT CaSnO l or BaSnOj ; AE = nuclear quadrupole splitting; r= full
width at half height of the resonant peaks. Spectra were taken at 77.3 K (liquid N2 temperature)
unless otherwise stated.
c Average data from 27 spectra in the r range indicated, with standard error.
ing to tin by two adjacent phospho diester groups of the DNA chain, and by a phosphodiester adjacent to Sn in the toroidal (Bloomfield 1996) DNA condensate, thus originating the apparent polymeric nature of tin bonding environment (Posante 1996).
Systems Alk 2 SnCI2(EtOH)n + DNA (Alk = Me, Et, No. 5-8, Table 12.2), appear to consist of species Alk2Sn(DNA monomerh, according to molecular dynamics studies on
lyophilized condensates (Barbieri et a1.1992; Barbieri et a1.1995; Posante 1996). Tin environment in gelled and lyophilized systems would be of trans-R2 octahedral type, such
as in Fig. 12.1b. In freeze-dried specimens, two coordination sites of type 12.1b would
occur for each system, according to the fitting of each experimental spectrum with
two symmetric doublets: Me2Sn(DNA monomerh, Mexp = 4.44 mm S-I, CSnC = 180°,
a~d LlEexp = 3.52 mm S-I, CSnC = 143\Et2Sn(DNA monomer}z, LlEexp = 4.35 mm S-I,
CSnC = 180
0
,andMexp = 3.56 mm s-I,CSnC = 145°; angles are estimated by point-charge