CHAPTER 12 • 119Sn Mossbauer Spectroscopy Studies: Organotin(lV) Salts and Complexes
237
Table 12.4. 119Sn Mossbauer parameters for DNA condensates (gels) obtained by interaction with DNA
of complexes ofMe2Sn(IV) and MeSn(IV) with 2-mercaptopyridine (HSPy)a and 2-mercaptopyrimidine
(HSPym)a
No. System
b
t
I'1F
T C
T C
References
,
2
(mms-')
(mms-')
(mms-')
(mms-')
Me 2 SnCI(SPy)+DNA
Rossi 1994;
doublet A:
1.31 - 1.26 3.96 - 4.55 0.70 - 0.86 0.70 - 0.86
Barone 1997;
doublet B
1.07 - 1.19 2.89- 3.28 0.84- 1.06 0.84 - 1.06
Barbieri et al. 1999
2 Me 2 SnCI(SPym)+DNA
doublet A:
1.24 - 1.38 4.41 - 4.47 0.75 - 0.81 0.75 - 0.81
doublet B
1.18-1.27 3.13 - 3.18 0.92 - 1.12 0.92-1.12
3 MeSnCI 2 (SPy)+DNA
0.57
2.19
0.85
0.88
Rossi 1994;
Barone 1997
4 MeSnCI 2 (SPym)+DNA 0.55
2.21
0.87
0.87
5 MeSnCI (SPY)2+DNA
0.53
2.01
1.07
1.02
6 MeSnCI (SPym)2+DNA 0.55
2.07
1.18
0.93
Barone 1997
(unpublished data)
a See Fig. 12.2.
b DNA condensates obtained by addition of ethanol solutions of the MenSn(lV)-SPy, SPym complexes
to aqueous buffered calf thymus DNA, the molar ratios r = [Sn) / [DNA monomer) = 1.0 being
employed for all samples; % C2HsOH $ 50 in the supernatants.
C See note b to Table 12.2. Average data, measured at 77.3 K, are reported, or data intervals. Data for
lyophilized specimens essentially correspond to the values for gelled systems here reported.
d Spectra fitted with two Lorentzian doublets, indicating the occurrence of two coordination sites to Sn.
in line with systems organotin chlorides-DNA (Table 12.2), and in analogy to assumptions for Et2SnCl2( o-phenanthroline)-DNA (Li et al. 1996b). The structure of tin environments in the DNA condensates, as extracted from the point-charge model treatment of the experimental LVJ 119Sn Mossbauer parameters (Table 12,4), are reported
in Fig. 12.3, where a further dissociation of N ~ Sn bonds is also accounted for, in
line with the orders of the magnitude of related stability constants (Sn-Sthio] > Snphosphate> Sn-Nhet; Hynes and O'Dowd 1987). Water coordination to tin is also taken
into account (Rossi 1994; Barone 1997).
Additional information on the nature of the interaction of complexes organotin(IV)-2-mercaptopyridine and -pyrimidine with DNA is extracted from the dynamics of tin by variable temperature 119Sn Mossbauer spectroscopy, effected on the representative DNA condensates listed in Table 12.5.
From the data in Table 12.5, the following is inferred:
1. The dynamics of tin in the assumed systems Me2Sn(SPym)(DNA monomer) and
MeSn(SPy)z(DNA monomer) consistently differ from data for MeSn(IV) and
Me2Sn(IV) complexes with S, N chelators (Barbieri A et al. 1995).
ii. Slopes of In(Arl A77.3) vs. T functions practically coincide in the gel and lyophilized
absorbers Me2Sn(SPym)(DNA monomer), being of the order of magnitude as
Alk2Sn(DNA monomerh, gel and lyophilized (Table 12.3).
237
Table 12.4. 119Sn Mossbauer parameters for DNA condensates (gels) obtained by interaction with DNA
of complexes ofMe2Sn(IV) and MeSn(IV) with 2-mercaptopyridine (HSPy)a and 2-mercaptopyrimidine
(HSPym)a
No. System
b
t
I'1F
T C
T C
References
,
2
(mms-')
(mms-')
(mms-')
(mms-')
Me 2 SnCI(SPy)+DNA
Rossi 1994;
doublet A:
1.31 - 1.26 3.96 - 4.55 0.70 - 0.86 0.70 - 0.86
Barone 1997;
doublet B
1.07 - 1.19 2.89- 3.28 0.84- 1.06 0.84 - 1.06
Barbieri et al. 1999
2 Me 2 SnCI(SPym)+DNA
doublet A:
1.24 - 1.38 4.41 - 4.47 0.75 - 0.81 0.75 - 0.81
doublet B
1.18-1.27 3.13 - 3.18 0.92 - 1.12 0.92-1.12
3 MeSnCI 2 (SPy)+DNA
0.57
2.19
0.85
0.88
Rossi 1994;
Barone 1997
4 MeSnCI 2 (SPym)+DNA 0.55
2.21
0.87
0.87
5 MeSnCI (SPY)2+DNA
0.53
2.01
1.07
1.02
6 MeSnCI (SPym)2+DNA 0.55
2.07
1.18
0.93
Barone 1997
(unpublished data)
a See Fig. 12.2.
b DNA condensates obtained by addition of ethanol solutions of the MenSn(lV)-SPy, SPym complexes
to aqueous buffered calf thymus DNA, the molar ratios r = [Sn) / [DNA monomer) = 1.0 being
employed for all samples; % C2HsOH $ 50 in the supernatants.
C See note b to Table 12.2. Average data, measured at 77.3 K, are reported, or data intervals. Data for
lyophilized specimens essentially correspond to the values for gelled systems here reported.
d Spectra fitted with two Lorentzian doublets, indicating the occurrence of two coordination sites to Sn.
in line with systems organotin chlorides-DNA (Table 12.2), and in analogy to assumptions for Et2SnCl2( o-phenanthroline)-DNA (Li et al. 1996b). The structure of tin environments in the DNA condensates, as extracted from the point-charge model treatment of the experimental LVJ 119Sn Mossbauer parameters (Table 12,4), are reported
in Fig. 12.3, where a further dissociation of N ~ Sn bonds is also accounted for, in
line with the orders of the magnitude of related stability constants (Sn-Sthio] > Snphosphate> Sn-Nhet; Hynes and O'Dowd 1987). Water coordination to tin is also taken
into account (Rossi 1994; Barone 1997).
Additional information on the nature of the interaction of complexes organotin(IV)-2-mercaptopyridine and -pyrimidine with DNA is extracted from the dynamics of tin by variable temperature 119Sn Mossbauer spectroscopy, effected on the representative DNA condensates listed in Table 12.5.
From the data in Table 12.5, the following is inferred:
1. The dynamics of tin in the assumed systems Me2Sn(SPym)(DNA monomer) and
MeSn(SPy)z(DNA monomer) consistently differ from data for MeSn(IV) and
Me2Sn(IV) complexes with S, N chelators (Barbieri A et al. 1995).
ii. Slopes of In(Arl A77.3) vs. T functions practically coincide in the gel and lyophilized
absorbers Me2Sn(SPym)(DNA monomer), being of the order of magnitude as
Alk2Sn(DNA monomerh, gel and lyophilized (Table 12.3).