Syntheses and characterisation of mercury complexes of sulfadiazine, sulfamerazine and sulfamethazine

Polyhedron 26 (2007) 967–974 www.elsevier.com/locate/poly

Syntheses and characterisation of mercury complexes of sulfadiazine, sulfamerazine and sulfamethazine G.M. Golzar Hossain, A.J. Amoroso *, A. Banu, K.M.A. Malik School of Chemistry, Cardiff University, Main Building, Cardiff, Wales CF10 3AT, United Kingdom Received 2 August 2006; accepted 22 September 2006 Available online 29 September 2006

Abstract The triple sulfa drugs, sulfadiazine, sulfamerazine and sulfamethazine, form a large number of metal complexes in different solvent media. The present studies show the synthesis and characterization of the Hg(II) complexes of sulfadiazine 1, sulfamerazine 2 and sulfamethazine 3 in dimethylformamide solution in presence of ammonia. The compounds were characterised by spectroscopic methods and crystal structures of the complexes were determined. All the compounds, 1, 2 and 3, crystallise in monoclinic crystal systems with the space groups of C2/c, C2/c and P21/c, respectively. Compounds 1 and 3 have eight coordinate ‘2+6’ geometries, with two tridentate sulfonamide ions and two DMF molecules in the coordination sphere. Complex 2 has a six co-ordinate, ‘2+4’ geometry which contains a short linear N–Hg–N moiety from co-ordinated sulfonamides. The IR spectral data suggest the binding of mercury atom to the sulfonamidic nitrogen atoms in agreement with the crystal structure determination.  2006 Elsevier Ltd. All rights reserved. Keywords: Triple sulfa drug; Mercury; Sulfadiazine; Sulfamerazine; Sulfamethazine

1. Introduction The co-ordination chemistry of mercury(II) differs from most other transition metals due to its large size and d10 configuration. Its interference in biological systems, and its potential as a toxin or as a medicine, has required a better understanding of its co-ordinative properties [1,2]. The stereochemistry of the ion is typically characterised by a co-ordination number of 2, but it is often expanded to an effective co-ordination number of ‘2+4’, due to its large Van der Waals radius [3]. In addition, the metal may be considered as a soft acceptor and one would expect it to interact best with soft bases. The three sulfa drugs, sulfadiazine, sulfamerazine and sulfamethazine, commonly called ‘triple sulfa drugs’, were introduced in medical therapy because they possessed *

Corresponding author. Tel.: +44 29 2087 4077; fax: +44 29 2087 4030. E-mail address: amorosoaj@cardiff.ac.uk (A.J. Amoroso).

0277-5387/$ - see front matter  2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2006.09.056

antibacterial activities. A few metal complexes of sulfa drugs such as copper [4], zinc [5–7], silver [8,9], cadmium [10] and mercury [11] complexes of sulfadiazine and copper [12] and cadmium [13] complexes of sulfamethazine have been reported. Metal complexes of sulfamerazine are not known and only the crystal structure of sulfamerazine has been reported. Many sulfonamide derivatives possess antibacterial activity including sulfamerazine which has strong antibacterial properties [14]. A few Hg complexes of sulfonamides are still used in topical medicine as an antiseptic, even though it is known that the interaction of heavy metal ions with biomolecules can have potentially toxic effects. The presence of several potential donor sites e.g., amino, pyrimido and sulfonamidic nitrogen; and sulfonyl oxygen atoms make them versatile complexing agents. This work describes the synthesis of new mercury complexes of ‘triple sulfa drugs’ and describes their solid state structure as determined by crystallography.

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R1

O H2N

S O

N N H

N R2

Sulfadiazine (sdr) when R1 and R2 are hydrogen (H) Sulfamerazine (smr) when R1 is H and R2 is methyl group (CH3) Sulfamethazine (smz) when R1 and R2 are methyl group (CH3)

The diversity of the coordination numbers for the mercury complexes can be found in the literature. In monoorganomercury(II) compounds, the primary bonds leave the Hg atom with enough residual acidity for it to be able to reach a coordination number of six when the donor atoms forming the secondary bonds are small. There are only a small number of Hg complexes with coordination number two [15]. However, Hg(II), has an extremely high affinity for thiol-containing compounds, and forms 1:2 metal: ligand linear complexes with them [16]. In this context, we will discuss the syntheses, spectroscopic characterization and X-ray crystal structure determination of the Hg complexes of sulfa drugs sulfamerazine sulfadiazine and sulfamethazine. 2. Experimental 2.1. General procedures Analar grade chemicals (SIGMA and BDH) were used as received. CHN microanalysis was carried out using a Perkin–Elmer 2400 CHN elemental analyzer. The IR spectra were recorded on a Nicolet 510 FTIR spectrometer, each compound was pressed into a KBr disk that was prepared in a sample holder by compressing a powdered sample with a 20-fold excess of dry KBr. NMR spectra were recorded on a Bruker Avance AMX-400 spectrometer. 1 H and 13C NMR spectra were obtained from a solution of the compounds in d6-DMSO. The chemical shifts are expressed in ppm relative to internal TMS.

of (CH3COO)2Hg (0.319 g, 1 mmol) was added with constant stirring. A white precipitate was formed and stirring continued for 6 h. It was filtered and dried over silica gel in a dessicator. The precipitate was dissolved in DMF and a few drops of ammonia was added and stirred for 30 min. The solution was filtered and left to crystallize. A few days later, white block crystals were obtained. The compound is soluble in DMF and DMSO but insoluble in water, alcohol and acetonitrile. Anal. Found: C, 36.89, H, 3.85; N, 16.53%. Calc. for C26H32HgN10O6S2: C, 36.94; H, 3.82; N, 16.57%. IR: (KBr disc): cm1, 3467(s), 3365(s), 3048(m), 2930, 1655(s), 1614(vs), 1588(vs), 1557(vs), 1506(vs), 1440(sh), 1414(vs), 1342(s), 1291(vs), 1184(w), 1127(sh), 1086(s), 994(w), 958(w), 907(s), 820, 682(s), 651(w), 574(vs), 547(vs), 518(vw), 457(vw), 416(w); 1 H NMR (400 MHz, DMSO-d6): d 8.50 [2H, d, J = 4.9, C(12/14)], 7.78 [2H, d, J = 8.5, C(16/20)], 6.98 [1H, t, J = 4.8, C(13)], 6.56 [2H, d, J = 8.6, C(17/19)], 5.92 [2H, s, (–NH2)]. 13C NMR (100.6 MHz, DMSO-d6): d 162.7 [C(12/14)], 158.8 [C(11)], 153.0 [C18], 130.6 [C(16/20)], 126.1 [C(15)], 114.7 [C(13)], 112.4 [C(17/19)]. 2.2.2. Preparation of the complex [Hg(smr)2] (2) As with the previous experiment, but sulfamerazine (0.530 g, 2 mmol) was used instead of sodium sulfadiazine. The compound is soluble in DMF and DMSO but insoluble in water, alcohol and acetonitrile. Anal. Found: C, 36.59, H, 3.02; N, 15.57%. Calc. for C22H22HgN8O4S2: C, 36.34; H, 3.05; N, 15.41%. IR: (KBr disc): cm1, 3436(s), 3317(s), 3228(m), 1632(vs), 1598(vs), 1571(vs), 1501(vs), 1465(sh), 1435(vs), 1392(vs), 1371(s), 1332(m), 1310(sh), 1281(vs), 1259(m), 1189(m), 1135(sh), 1093(s), 1010(w), 971(w), 945(w), 917(s), 869(w), 823, 792(s), 769(vw), 716(vw), 689(s), 635(w), 582 (vs) and 546; 1H NMR (400 MHz, DMSO-d6): d 8.37 [1H, d, J = 5.1, C(14)], 7.84 [2H, d, J = 8.5, C(16, 20)], 6.92 [2H, d, J = 5.1, C(17, 19)], 6.63 [1H, d J = 8.8, C(13)], 5.97 [2H, s, (–NH2)], 2.39 [3H, s, (CH3)]. 13C NMR (100.6, DMSO-d6): d 168.4 [C(11)], 161.4 [C(12)], 158.3 [C(14)], 152.9 [C(18)], 130.8 [C(15)], 126.2 [C(16/20)], 114.1 [C(17/19)], 112.2 [C(13)], 23.6 [CH3].

2.2. X-ray crystallography The crystallographic measurements for the complexes were made at 150 K on a Bruker Nonius Kappa CCD area detector using graphite monochromatised Mo Ka radia˚ . The structures were solved by direct tion, k = 0.71073 A methods (SHELXS-97) [17] and refined on F2 by full-matrix least squares (SHELXL-97) [18] using all unique data and parameters. The absorption correction was made by multi-scan method [19]. The hydrogen atoms on the amino groups of sulfa drugs in the complexes were located from the difference Fourier maps and refined freely. 2.2.1. Preparation of the complex [Hg(sdz)2(DMF)2] (1) Sodium salt of sulfadiazine (0.545 g, 2 mmol) was dissolved in hot methanol and to this, a methanolic solution

2.2.3. Preparation of the complex [Hg(smz)2(DMF)2] (3) With the same procedure in experiment 2.2.1 except the sodium salt of sulfamethazine (0.601 g, 2 mmol) was used instead of sodium sulfadiazine. The compound is soluble in DMF and DMSO but insoluble in water, alcohol and acetonitrile. Anal. Found: C, 39.72, H, 4.58; N, 15.51%. Calc. for C30H40HgN10O6S2: C, 39.97; H, 4.47; N, 15.54%. IR: (KBr disc): cm1, 3457(s), 3360(s), 3247(m), 2919, 1660(vs), 1599(vs), 1577(vs), 1547(vs), 1506, 1429(sh), 1393(vs), 1373(s), 1332(m), 1292(vs), 1258(m), 1194 (w), 1137(sh), 1086(s), 994(w), 965, 897(w), 820, 779(vw), 682(s), 635(w), 589(vs), 549(vs). 1H NMR (400 MHz, DMSO-d6): d 7.80 [2H, d, J = 8.6 Hz, C(16/ 20)], 6.57 [2H, d, J = 8.7, C(17/19)], 6.69 [1H, s, C(13)], 5.90 [2H, s, (–NH2)], 2.51 [6H, s, CH3]. 13C NMR

G.M. Golzar Hossain et al. / Polyhedron 26 (2007) 967–974

4. 1H NMR and

(DMSO-d6): d 167.9 [C(11)], 159.6 [C(12/14)], 152.8 [C(18)], 131.0 [C(15)], 126.3 [C(16/20)], 113.1 [C(17/C19)], 112.0 [C(13)], 23.5 [CH3].

13

969

C NMR spectra

Due to these compounds being insoluble in less polar solvents, 1H and 13C NMR spectra were obtained from a solution of the complex in d6-DMSO. The chemical shifts are expressed in ppm relative to internal TMS. The NMR data is presented in Tables 2–4. The data shows that while the ligands are present in the complex, they only display very small shifts in comparison to the free ligands. The most notable feature is the sulfonamidic proton and correspondingly the relatively large shift of the carbon signal (C11) next to the amide. Whether or not the structure of the complex is retained in solution, or if it exists as solvated cation and ligand anion can not be determined from these spectra.

3. IR spectra The infrared spectra of the complexes taken in the region 4000–400 cm1 were compared with those of the free ligands. The bands that appear between 3500 and 3400 cm1 due to asym(NH2) and sym(NH2) vibrations of the amino (–NH2) group [13–20] are modified with respect to those of the free respective ligands. These modifications are most probably due to the hydrogen bonding between complexes involving the NH2 and SO2 groups. The peak for the sulfonamidic (N–H) group in the free ligands at around 3125 cm1, are not present in the spectra of the complexes, confirming the deprotonation of the –SO2NH– moiety. The scissoring vibrations for the amino (–NH2) groups appear in the range of 1614–1662 cm1 and peaks due to phenyl ring appear at around 1547 and 1600 cm1. The peaks around 1325 and 1331 cm1 are assigned to mas(SO2), and those at 1155–1157 cm1 to msy(SO2), show significant changes upon complexation. The first one splits into two peaks at 1291–1386 cm1 and the second appears at around 1131–1194 cm1 in the complexes. The 945–965 cm1 bands in the ligands are assigned to m(S–N) [20] and are at higher frequencies (958– 1046 cm1) in all cases, as a consequence of coordination to the metal. This shift to higher frequencies is in accordance with the shortening of the S–N bond lengths, which have been observed in the crystal structures of complexes (see Table 1).

5. Crystal structure of the complexes 1, 2 and 3 Single crystals suitable for X-ray determination were obtained for the complexes by the slow evaporation of a DMF solution of the complex, in the presence of NH3. The crystal data and refinement details for the complexes are listed in Table 5. The crystal structures of the complexes [Hg(sdz)2(DMF)2] (1), [Hg(smr)2] (2) and [Hg(smz)2(DMF)2] (3) are shown in Figs. 1,3, and 5, respectively together with the crystallographic atom numbering scheme used. The selected bond lengths and angles are collected together in Table 6. The complexes [Hg(sdz)2(DMF)2] (1) and [Hg(smz)2(DMF)2] (3) have a ‘2+6’ geometry with the Hg atom lying on the two-fold axis. Both molecules contain two short ˚ ) as well Hg–N(11) amide distances (2.047(3)–2.050(3) A

Table 1 The IR spectra of the compounds 1–3 Complexes

–NH2

dNH2

Phenyl rings

(SO2)as

(SO2)sy

S–N

1 2 3

3467, 3365 3436, 3317 3457, 3360

1614 1632 1660

1588, 1557 1598, 1571 1599, 1577

1342, 1291 1371, 1281 1373, 1292

1184 1189 1194

994, 958 1010, 971 994, 965

Table 2 1 H NMR and

13

C NMR shift assignment of sulfadiazine and its Hg complex [Hg(sdz)2(DMF)2] (1) in DMSO-d6a

Assignment

1

N(11)–H C(11) C(12)–H/C(14)–H C(13)–H C(15) C(16)–H/C(20)–H C(17)–H/C(19)–H C(18) NH2

11.35

a b

1

H(HsdzH)

H1

8.50 7.00

8.48 6.98

7.75 6.58

7.78 6.56

6.00

13

13

158.6 157.5 115.9 125.1 130.3 112.6 153.4

162.7 158.8 114.7 126.1 130.6 112.4 153.0

C(HsdzH)

5.92 1

Relative to TMS with DMSO-d6 peak as reference ( H, 2.60 ppm, Dd = d(complex)  d(sdz).

C1

Dd (H)b

0.02 0.02 +0.03 0.02 +0.08

13

C, 43.5 ppm).

Dd (C)b +4.1 +1.3 1.2 +1.8 +0.3 0.2 0.4

970 Table 3 1 H NMR and

G.M. Golzar Hossain et al. / Polyhedron 26 (2007) 967–974

13

C NMR shift assignment of sulfamerazine and its Hg complex [Hg(smr)2] (2) in DMSO-d6a

Assignment

1

N(11)–H C(11) C(12) C(13)–H C(14)–H C(15) C(16)–H/C(20)–H C(17)–H/C(19)–H C(18) NH2 CH3

11.20

a b

6.62 8.37

6.63 8.37

7.69 6.95

7.84 6.92

6.07 2.41

5.97 2.39

13

13

13

164.3 157.5 112.1 156.8 130.1 124.9 114.7 152.9

168.4 161.4 112.2 158.3 130.8 126.2 114.1 152.9

23.3

23.6

C(smrH)

C2

Dd (H)b

+0.01 0.00 +0.15 0.03

Dd (C)b +4.1 +3.9 +0.1 +1.5 +0.7 +1.3 0.6 0.0

0.10 0.02

+0.3

Dd (H)b

Dd (C)b

13

C, 43.5 ppm).

C NMR shift assignment of sulfamethazine and its mercury complex (3) in DMSO-d6a

Assignment

1

N(11)–H C(11) C(12)/C(14) C(13)–H C(15) C(16)–H/C(20)–H C(17)–H/C(19)–H C(18) NH2 CH3

11.20

b

H2

Relative to TMS with DMSO-d6 peak as reference (1H, 2.60 ppm, Dd = d(complex)  d(smr).

Table 4 1 H NMR and

a

1

H(smrH)

1

H(smzH)

H3

6.45

6.57

7.69 6.60

7.80 6.69

5.98 2.22

5.90 2.51

Relative to TMS with DMSO-d6 peak as reference (1H, 2.60 ppm, Dd = d(complex)  d(smz).

13

13

165.6 157.0 112.3 130.8 125.4 114.0 153.2

167.9 159.6 113.1 131.0 126.3 112.0 152.8

23.4

23.5

C(smzH)

C3

+0.12 +0.11 0.09 0.08 +0.29

+2.3 +2.6 +0.8 0.3 +0.9 2.0 0.4 +0.1

13

C, 43.5 ppm).

Table 5 Crystal data and details of data collection and structure refinement for the complexes [Hg(sdz)2 (DMF)2] (1), [Hg(smr)2] (2) and [Hg(smz)2(DMF)2] (3) Empirical formula Formula weight Crystal system Space group ˚) a (A ˚) b (A ˚) c (A b () ˚ 3) V (A Z T (K) Crystal size (mm) Shape Colour Dcal h Range for data collection Reflection collected Unique reflections Rint Index ranges Goodness-of-fit on F2 Data/parameters Final R indices [I > 2r(I)] R indices (all data) ˚ 3) Largest difference in peak and hole (A

1

2

3

C26H32HgN10O6S2 845.33 monoclinic C2/c 20.0760(5) 8.3210(3) 19.8380(6) 108.6592(16) 3139.61(17) 4 150 0.12 · 0.10 · 0.08 block white 1.788 3.01–27.46 14 863 3570 0.0761 26 6 h 6 25; 10 6 k 6 10; 25 6 l 6 25 1.043 3570/214 0.0373/0.0629 0.0523/0.0679 1.248 and 0.895

C22H22HgN8O4S2 727.19 monoclinic C2/c 12.8834(5) 14.5693(5) 12.7683(6) 97.5505(14) 2375.86(17) 4 150 0.15 · 0.12 · 0.08 block white 2.033 3.19–27.46 16 902 2713 0.0866 16 6 h 6 16; 18 6 k 6 18; 16 6 l 6 16 1.107 2713/177 0.0386/0.0843 0.0465/0.0873 1.130 and 2.001

C30H40HgN10O6S2 901.43 monoclinic P21/c 12.4196(2) 8.8066(2) 17.0090(3) 107.9790(12) 1769.22(6) 2 150 0.16 · 0.12 · 0.10 block white 1.692 2.93–27.48 14 760 4042 0.0660 16 6 h 6 16; 11 6 k 6 11; 21 6 l 6 22 1.049 4042/235 0.0283/0.0631 0.0435/0.0685 0.509 and 0.983

G.M. Golzar Hossain et al. / Polyhedron 26 (2007) 967–974

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Fig. 3. X-ray structure of [Hg(smr)2] (2) showing crystallographic atom numbering scheme used. Thermal ellipsoids are drawn at 50% probability level. The hydrogen atoms are omitted for clarity. Fig. 1. X-ray structure of [Hg(sdz)2(DMF)2] (1) showing crystallographic atom numbering scheme used. Thermal ellipsoids are drawn at 50% probability level. The hydrogen atoms are omitted for clarity.

Fig. 4. Packing diagram of the complex [Hg(smr)2] (2) showing hydrogen bonds by open bonds and long interactions by dashed lines.

Fig. 2. Packing diagram of the complex [Hg(sdz)2(DMF)2] (1) showing the hydrogen bonds by dashed lines.

as six other longer Hg–O/N interactions. These interactions derive from the additional co-ordination of one sulfoxide and one pyrimidine donor of each sulfa drug ligand, as well as two molecules of DMF co-ordinated to each metal. The three donor atoms from each sulfa ligand (N(11), N(13) and O(12)) and the Hg atom all lie within

a plane. While at first it might appear that the six donors from the two sulfa ligands might define a distorted hexagonal planar array, the two planes defined by the ligands and the central mercury atom are slightly offset. The DMF molecules are coordinated to the Hg atom and may almost be considered as axial donors to the six equatorial donors of the sulfa ligands. By contrast, the [Hg(smr)2] complex 2 has a ‘2+4’ coordination geometry with two molecules of sulfamerazine coordinated with short Hg–N distances through the sulfonamidic nitrogen atoms. Due to the steric constraints of the ligand, the other donors (N(13) and O(12)) are in close

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Fig. 5. X-ray structure of [Hg(smz)2(DMF)2] (3) showing crystallographic atom numbering scheme used. Thermal ellipsoids are drawn at 50% probability level. Hydrogen atoms are omitted for clarity.

Table 6 ˚ ] and angles [] in the complexes Selected bond lengths [A [Hg(sdz)2(DMF)2] (1), [Hg(smr)2] (2) and [Hg(smz)2(DMF)2] (3) 1a

2a

3b

Bond Hg–N(11) Hg–O(1) Hg–O(12) Hg–N(13)

2.047(3) 2.713(3) 2.966(3) 2.938(4)

2.017(4) 2.832(4) 3.014(4)

2.050(3) 2.727(2) 3.027(2) 2.918(3)

S(11)–O(11) S(11)–O(12) S(11)–N(11) S(11)–C(15) N(11)–C(11) N(14)–C(18)

1.443(3) 1.444(3) 1.630(4) 1.759(4) 1.386(6) 1.384(6)

1.433(4) 1.444(2) 1.648(4) 1.749(5) 1.397(6) 1.369(7)

1.444(3) 1.445(2) 1.636(3) 1.756(3) 1.392(4) 1.375(4)

179.4(2) 76.93(12) 86.04(14) 104.34(9) 50.70(12) 128.79(9) 128.75(13) 126.69(12) 53.88(12) 153.79(9) 73.71(10) 162.73(16) 87.99(12) 92.09(12) 92.61(10) 113.06(10) 80.08(11) 127.1(4)

171.5(2) 97.96(17) 119.58(16) 105.93(11) 49.33(14) 112.71(11) 136.59(11) 116.93(15) 56.60(14) 112.71(11)

Angle N(11)–Hg–N(11 0 ) O(12)–Hg–O(12 0 ) N(13)–Hg–N(13 0 ) N(13)–Hg–O(12) N(13)–Hg–N(11) N(13)–Hg–O(12 0 ) N(13)–Hg–N(11 0 ) N(11)–Hg–O(12 0 ) N(11)–Hg–O(12) N(13 0 )–Hg–O(12) O(1 0 )–Hg–O(12) O(1)–Hg–O(1 0 ) N(11)–Hg–O(1) O(1)–Hg–N(11 0 ) O(1)–Hg–O(12) O(1)–Hg–N(13 0 ) O(1)–Hg–N(13) N(13)–C(11)–N(12)

128.0(5)

180.0 180.0 180.0(11) 104.12(7) 51.29(9) 75.88(7) 128.71(9) 127.17(9) 52.83(9) 75.88(7) 92.01(7) 180.0 94.75(9) 85.25(9) 87.99(7) 83.39(8) 96.61(8) 127.7(3)

Symmetry transformations used to generate equivalent atoms: (a) x, y, z + 1/2; (b) x, y + 1, z.

proximity to the sulfonamidic donor. The closeness of these donors leads to open spaces about the metal centre and an irregular co-ordination sphere. However, the open spaces about the metal centre are apparently not sufficiently large to fit two extra solvent molecule donors. While the comparative steric congestion of the metal centre, as compared to the sulfadiazine complex, might explain the lack of co-ordinated solvent molecules, there is no obvious reason why this molecule would be any more congested than the sulfamethazine complex (with an additional methyl substituent), whose crystal structure also has two co-ordinated solvent molecules. Ultimately, these crystal structures may be determined by crystal packing forces and the observed structures only offer suggestions of their structure in solution. In solution, the structure of 2 may be identical to that of 1 and 3. In complexes 1 and 3, the long Hg–O(1) distances from ˚ for 1 and 2.727(2) A ˚ for 3 are the DMF donors (2.713(3) A slightly shorter than the corresponding bond Hg–O(1) in ˚ ) [11]. The short Hg– [Hg(sdz)2(DMSO)2] (2.769(7) A ˚ for 1, 2.017(4) A ˚ for N(11) bond distances of 2.047(3) A ˚ for 3 are also comparable with those of 2 and 2.050(3) A ˚) [Hg(smpz)2] (2.071(4) A [13], [Hg(sdz)2(DMSO)2] ˚ ) [11], [Hg(mq)2] (2.041(6) and 2.031(6) A ˚ ) [21] (2.087(4) A ˚ ) [22] and [Hg(bpy)2(NO2psgly-N,O)]0.5H2O (2.14(2) A (where smpz, sdzH, mq and NO2psgly are sulfamethoxypiridazine, sulfadiazine, 4-methyl-2(1H)-quinoline and N2-nitrophenylsulfonylglycine, respectively). ˚ in 1, The C(18)–N(14) bond distances of 1.384(6) A ˚ in 2 and 1.375(4) A ˚ in 3 are in good agreement 1.369(7) A with the corresponding bond in the pure ligands [23]. It is also comparable with the corresponding bond found in the mercury–sulfadiazinato complex [Hg(sdz)2(DMSO)2] ˚ ]. Typically if the terminal amino group [11] [1.383(14) A ˚ are is co-ordinated, N–C bond lengths of about 1.413(9)A expected [13]. Interestingly, the geometry about the Hg atom in complexes 1 and 3 results in a mutually square planar arrangement of the sulfonamidic and solvent molecules donors. This arrangement is fairly regular showing only minor variations from ideal geometry of the mutually cis 90 and trans 180 angles. This is evident from the values of trans angles for N(11 0 )–Hg(1)–N(11) (179.4(2)) and O(1 0 )– Hg(1)–O(1) (162.7(2)) for 1 and 180.0 for 3. The cis angles vary from 88.0(1) to 92.1(2) in the complex 1 and 85.2(2)–94.8(2) in the complex 3. Complex 2 lies on a two-fold axis in which the sulfamerazinato ligands are bonded to the Hg-atom through the sulfonamidic nitrogen [N(11)] atom with a N(11)–Hg–N(11 0 ) angle of 171.5(2) indicating the ‘linearity’ of the complex. When bonded to mercury the ligand acts as a tridentate donor, albeit with two very long and one short interaction. Never the less, the ‘tridentate’ coordination mode of this ligand is particularly rare. Typically, ligands such as pyridyl sulfonamides form complexes where the ligand is monodentate or bidentate. Typical examples are of bidentate co-ordination where the nitrogen of the heterocycle

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Table 7 ˚ ) and angles ()] Dimensions of the hydrogen bonds in complexes 1, 2 and 3 [distances in (A D–H    A a

N14–H14A . . . O12 N14–H14B . . . N13b N14–H14A . . . N13c N14–H14B . . . O12d N14–H14A . . . O11e N14–H14B . . . O11f a b c d e f

Compounds

D–H

D  A

H  A


1 1 2 2 3 3

0.950(8) 0.949(5) 0.931(3) 0.937(6) 0.948(8) 0.949(8)

3.244(4) 3.210(2) 3.323(7) 3.173(7) 3.031(1) 3.038(7)

2.346(2) 2.452(1) 2.583(4) 2.399(7) 2.104(8) 2.223(4)

157.75(3) 136.74(3) 136.78(2) 139.93(5) 165.47(3) 143.46(6)

x  1/2, +y + 1/2,  z + 1/2. x  1/2, +y  1/2, +z. x + 1/2, +y  1/2, +z. x, y, +z + 1/2. x + 1, +y  1/2, z + 1/2. x, y + 1/2, +z + 1/2.

Fig. 6. Packing diagram of the complex [Hg(smz)2(DMF)2] (3) showing the hydrogen by dashed lines.

and the sulfonamidic nitrogen co-ordinate [24,25] or bidentate co-ordination of nitrogen of the heterocycle and the oxygen of the sulfoxide group co-ordinate [24–26]. The packing of these complexes in the solid state is strongly influenced by the extensive hydrogen bonding between (i) the amino (–NH2) group of one complex unit and the sulfonyl oxygen [N(14)–H(14A)    O(12) (of other ˚ with an angle of 157.75(3)] and complex unit): 2.346(2) A (ii) hydrogen bonding between the amino (–NH2) group of one complex unit and the pyrimido nitrogen atoms of the next unit, [N(14)–H(14B)    N(13) (other complex ˚ with an angle of 136.74(3)]. The packunit) = 2.452(1) A ing diagram of the complex [Hg(sdz)2(DMF)2] (1) is shown in Fig. 2 and dimensions of the hydrogen bonding is listed in Table 7. In the packing diagram of the complex 2 the amino group, sulfonyl oxygen and pyrimido nitrogen atoms are hydrogen bonded which is shown in Fig. 4 by dashed lines. Necessarily, the lack of DMF within the lattice leads to a different overall arrangement of hydrogen bonds, though the hydrogen bonding occurs between the same donors and acceptors See Fig. 5. However, on close inspection of the hydrogen binding network in 3, (Fig. 6), it can be seen

that now, the pyrimidine does not participate in hydrogen bonding and now both hydrogens of the amino group are hydrogen bonding to the sulfonyl oxygen of two different ligands. This change in hydrogen bonding is due, in some part, to the additional methyl group on the ligand which will sterically hinder the pyrimidine group. Acknowledgement The authors acknowledge the support of the School of Chemistry, Cardiff University, United Kingdom. Appendix A. Supplementary material CCDC 293146, 293147 and 293148 contain the supplementary crystallographic data for 1, 2 and 3. These data can be obtained free of charge via http://www.ccdc.cam. ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit @ccdc.cam.ac.uk. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/ j.poly.2006.09.056.

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