Complexes of Zn2+, Cd2+, and Hg2+ with 2-(α-Hydroxybenzyl)thiamine Monophosphate Chloride

Article abstract of DOI:10.1021/ic950758x

The binding sites of Zn²⁺, Cd²⁺, and Hg²⁺ in complexes with 2-(α-hydroxybenzyl)thiamine monophosphate chloride, (LH)⁺Cl^-, have been investigated in the solid state [2-(α-hydroxybenzyl)thiamin monophosphate chloride monoprotonated at the phosphate group and protonated at N_1′ is denoted as (LH)⁺C1^-; therefore, the ligand monoprotonated at the phosphate group and deprotonated at N_1′ is L]. Complexes of formulae MLCl₂, M(LH)-Cl₃, and (MCl₄)^2-(LH)₂⁺ (M = Zn²⁺, Cd²⁺, and Hg²⁺) were isolated in aqueous and methanolic solutions, depending on pH. The crystal structure of the complex of formula HgL₂Cl₂ was solved, together with that of the free ligand (LH)⁺Cl^-, by X-ray crystallography. HgL₂Cl₂ crystallizes in C2/c, with a = 32.968(6) A?, b = 7.477(2) A?, c = 21.471(4) A?,β= 118.19(1)°, V = 4665(2) A?³, and Z = 4. (LH)⁺C^l- crystallizes in Cc, with a = 10.951(3) A?, b = 17.579(4) A?, c = 13.373(3) A?, β= 105.36(2)°, V = 2482.4(10) A?³3, and Z = 4. Mercury(II) binds to the N(1′) of the pyrimidine ring. Both ligands are in the S conformation [φ_T = -98.1(9)° and φ_p = 176.1(10)° for HgL₂Cl₂ and φ_T = 104.1(5)° and φ_p = 171.9(6)° for (LH)⁺Cl^-]. ³¹P and ¹³C NMR spectra, together with vibrational spectra (IR/Raman), are used to deduce the binding sites of the metal and the protonation states of the ligand at various pH values. It is found that solid-state ³¹P NMR spectroscopy is particularly useful in characterizing these complexes as the ³¹P shielding tensors are sensitive to the state of the phosphate group. On the other hand, the ³¹P NMR spectra indicate that direct bonding between Zn²⁺ and Cd²⁺ to the phosphate can occur under certain preparation conditions. Solid-state ¹³C NMR and vibrational (IR/Raman) spectroscopic results are also in agreement with the other techniques.

Full text of DOI:10.1021/ic950758x

Inorg. Chem. 1996, 35, 6513-6519
6513
Complexes of Zn2+, Cd2+, and Hg2+ with 2-(r-Hydroxybenzyl)thiamine Monophosphate
Chloride
Katerina Dodi,† Ioannis P. Gerothanassis,† Nick Hadjiliadis,*,† Andre Schreiber,‡
Robert Bau,‡ Ian S. Butler,§ and Patrick J. Barrie|,
Department of Chemistry, University of Ioannina, Ioannina 45-110, Greece, Department of Chemistry,
University of Southern California, Los Angeles, California 90089-1062, Department of Chemistry,
McGill University, 801 Sherbrooke Street West, Montreal, PQ, H3A 2K6 Canada, and Department of
Chemistry, University College London, 20 Gordon Street, London WC1H OAJ, U.K.
ReceiVed June 15, 1995X
The binding sites of Zn2+, Cd2+, and Hg2+ in complexes with 2-(R-hydroxybenzyl)thiamine monophosphate
chloride, (LH)+Cl-, have been investigated in the solid state [2-(R-hydroxybenzyl)thiamin monophosphate chloride
monoprotonated at the phosphate group and protonated at N1′ is denoted as (LH)+Cl-; therefore, the ligand
monoprotonated at the phosphate group and deprotonated at N1′ is L]. Complexes of formulae MLCl2, M(LH)-
Cl3, and (MCl4)2-(LH)2+ (M ) Zn2+, Cd2+, and Hg2+) were isolated in aqueous and methanolic solutions, depending
on pH. The crystal structure of the complex of formula HgL2Cl2 was solved, together with that of the free ligand
(LH)+Cl-, by X-ray crystallography. HgL2Cl2 crystallizes in C2/c, with a ) 32.968(6) Å, b ) 7.477(2) Å, c )
21.471(4) Å, â ) 118.19(1)°, V ) 4665(2) Å3, and Z ) 4. (LH)+Cl- crystallizes in Cc, with a ) 10.951(3) Å,
b ) 17.579(4) Å, c ) 13.373(3) Å, â ) 105.36(2)°, V ) 2482.4(10) Å3, and Z ) 4. Mercury(II) binds to the
N(1′) of the pyrimidine ring. Both ligands are in the S conformation [ΦT ) -98.1(9)° and ΦP ) 176.1(10)° for
HgL2Cl2 and ΦT ) 104.1(5)° and ΦP ) 171.9(6)° for (LH)+Cl-]. 31P and 13C NMR spectra, together with
vibrational spectra (IR/Raman), are used to deduce the binding sites of the metal and the protonation states of the
ligand at various pH values. It is found that solid-state 31P NMR spectroscopy is particularly useful in characterizing
these complexes as the 31P shielding tensors are sensitive to the state of the phosphate group. On the other hand,
the 31P NMR spectra indicate that direct bonding between Zn2+ and Cd2+ to the phosphate can occur under
certain preparation conditions. Solid-state 13C NMR and vibrational (IR/Raman) spectroscopic results are also in
agreement with the other techniques.
Introduction
The pyrophosphate derivative of thiamine (vitamin B1) is
well-known to require the presence of divalent metal ions, such
as Mg2+ and Ca2+ in ViVo and Co2+, Zn2+, Mn2+, Cd2+ etc. in
Vitro, to act as a cofactor for enzymes involved in catalyzing
reactions such as the decarboxylation of R-keto acids or the
transfer of aldehyde and acyl groups (decarboxylase, transke-
tolase, etc.).1,2 It has been suggested that the metal acts as a
bridge between the apoenzyme and the thiamine cofactor.2
Because of this, there have been a number of studies attempting
to establish the role of the divalent cation by determining the
metal-binding site to the thiamine derivative.3 However, in
many cases ionic salt complexes form with a metal-containing
anion balancing the positive charge located on the thiazolium
ring.4,5 In those cases where direct bonding to thiamine is
observed, the metal normally forms a covalent bond to the N(1′)
site of the pyrimidine ring;6,7 however, complexes with coor-
dination to the hydroxyethyl oxygen of thiamine7,8 or the
pyrophosphate group of the pyrophosphate derivative are also
known.9 So-called “active aldehyde” derivatives (1, 2) are
known intermediates in the enzymatic process,10 and it has been
found that Zn2+, Cd2+, and Hg2+ bind to the N(1′) site of the
active aldehyde derivatives of thiamine (containing no phosphate
group) in both the solid state and solution.11,12
In this paper, we report solid-state NMR and vibrational
spectroscopy results on Zn2+, Cd2+, and Hg2+ complexes of
the active aldehyde derivative 2-(R-hydroxybenzyl)thiamine
monophosphate chloride [denoted (LH)+Cl- throughout this
paper for convenience] prepared at pH 3.5 and 5.5-6.0.
* Corresponding author.
† University of Ioannina.
‡ University of Southern California.
§ McGill University.
| University College London.
Current address: Dept. of Chemical Engineering, University of
Cambridge, Pembroke Street, Cambridge CB2 3RA, UK.
X Abstract published in AdVance ACS Abstracts, September 15, 1996.
(1) Scrutton, M. C. Inorg. Biochem. 1973, 1, 3.
(2) Schellenberger, A. Angew. Chem., Int. Ed. Engl. 1967, 6, 1024.
(3) Louloudi, M.; Hadjiliadis, N. Coord. Chem. ReV. 1994, 135, 429.
(4) Richardson, M. F.; Franklin, K.; Thomson, D. M. J. Am. Chem. Soc.
1975, 97, 3204.
(6) Cramer, R. E.; Maynard, R. B.; Ibers, J. A. J. Am. Chem. Soc. 1981,
103, 76.
(7) Aoki, K.; Yamazaki, H.; Adeyemo, A. Inorg. Chim. Acta 1991, 180,
117.
(8) Hu, N. H. Inorg. Chim. Acta 1991, 186, 209.
(9) Aoki, K.; Yamazaki, H. J. Am. Chem. Soc. 1980, 102, 6878.
(10) Breslow, R. J. Am. Chem. Soc. 1958, 80, 3719.
(5) Aoki, K.; Tokuno,T.; Takagi, K.;Hirose, Y.; Suh, I. H.; Adeyemo A.
O.; Williams, G. N. Inorg. Chim. Acta 1993, 210, 17.
S0020-1669(95)00758-0 CCC: $12.00 © 1996 American Chemical Society

6514 Inorganic Chemistry, Vol. 35, No. 22, 1996
Dodi et al.
4. Preparation of the (LH)2+(MCl4)2- Complexes (M ) Zn2+
,
Preparations at lower pH values have a tendency to form ionic
salt complexes of the type [LH+]2[MCl4]2- with no direct
binding between metal and thiamine. The spectroscopic results
provide indirect information on the metal-binding site. In
particular, the 31P solid-state NMR results enable the principal
components of the 31P shielding tensor to be obtained, which
sheds light on the state of the phosphate group and, hence, on
the mode of metal binding. The spectroscopic studies are
complemented by single-crystal X-ray structure determinations
of the uncomplexed molecule (LH)+Cl- prepared at pH 3.5 and
the mercury complex HgL2Cl2. Unfortunately we have not been
able to prepare crystals of Zn2+ or Cd2+ complexes with L of
sufficient quality for X-ray structure determination. However,
the agreement between the conclusions drawn from the spec-
troscopic data and the crystal structure of the Hg2+ complex
means that we can be fairly confident about inferences based
solely on spectroscopic data for the other complexes. It is found
for the first time that direct binding of the metal to the
monophosphate group can occur for the Zn2+ and Cd2+
complexes for preparations at certain pH values.
Cd2+, Hg2+). These were prepared by following the procedure used
for the MLCl2 complexes by adjusting the pH of both the ligand and
the metal chloride to about 1-1.5 using 0.1 N HCl solution (yields ∼
50%).
5. Preparation of HgL2Cl2. Equimolar amounts (1 mmol) of HgCl2
and the ligand (LH)+Cl- were mixed in aqueous solutions (20-30 mL)
after adjusting the pH to 5.5-6, using 0.1 N KOH solution. After the
mixture was stirred for 24 h at room temperature, the resulting
precipitate was filtered and washed with small quantities of water,
methanol, and ether. It was dried first at room temperature and then
at 55-60 °C in Vacuo, in the presence of CaCl2. The crystal structure
indicated that one molecule of water was present per thiamine unit
(yield ∼ 90% based on HgCl2).
6. Preparation of HgL2Cl2 Crystals. An aqueous solution (10
mL 10-2 M) of the ligand (LH)+Cl- and 10 mL of a 10-2 M solution
of HgCl2 in a mixture of ethanol and hexane (3:2) were mixed in a test
tube. The tube was left in the refrigerator, and after about 10 days
crystals of the complex appeared at the interface of hexane and water.
7. Deuteration Experiments. The deuterated ligands at various
pH’s and the complexes were prepared by dissolving small amounts
(30-40 mg) in about 1 mL of D2O, followed by lyophilization. The
deuterated HgL2Cl2 complex was prepared by carrying out the
preparation in D2O solution on a smaller scale (0.1 mmol).
Methods. 1. Crystal Structures. (a) The Ligand 2-(r-Hydroxy-
benzyl)thiamine Monophosphate Chloride Trihydrate ((LH)+Cl-‚
3H2O). A crystal of size 0.2 × 0.2 × 0.6 mm was mounted in a glass
capillary. Intensity data were collected with ω-scans, using a variable
Experimental Section
Materials. Thiamine monophosphate chloride was purchased from
Sigma Chemical Co. and used without further purification. ZnCl2,
CdCl2, and HgCl2 and all other chemicals used were from Aldrich AG.
Preparation of the Compounds. 1. Preparation of the Ligand
2-(r-Hydroxybenzyl)thiamine Monophosphate Chloride (LH)+Cl-.
2-(R-Hydroxybenzyl)thiamine monophosphate chloride was prepared
by employing a method analogous to that used for the preparation of
2-(R-hydroxybenzyl)thiamine11 but using thiamine monophosphate
chloride as the starting material.
scan speed (6.00-60.0° min-1 in ω) and a scan width of 2.0°.
A
Siemens P4 diffractometer with graphite-monochromated Mo KR
radiation was used for preliminary examination and data collection.
The lattice parameters were determined from a least-squares fit of the
setting angles of 45 reflections up to 2θmax of 25°. Three standard
reflections were recorded at 1000 reflection intervals, and random
deviations were detected during data collection. A total of 4159
reflections was measured with 4.0° < 2θ < 45.0°, having indices of
-7 < h < 11, -9 < k < 18, and -14 < l < 12. The data were
reduced and corrected for Lorentz polarization effects and averaged
(Rint ) 0.040) to 1832 unique reflections, 1752 of which had F > 4.0σ-
(F). The space group was determined to be Cc. The structure was
solved via direct methods. It was refined (on F) by using full-matrix
least squares with anisotropic displacement parameters of all non-
hydrogen atoms and a common isotropic displacement parameter for
the H-atoms, which were placed in geometrically calculated positions.
A total of 307 parameters was refined to R ) 0.035, wR ) 0.042, and
(∆/σ)max ) 0.091. The programs used were SHELX 76 (Sheldrick,
1976) and TEXSAN (Molecular Structure Corporation Version 1.6,
1993).
(b) The Complex Bis[2-(r-hydroxybenzyl)thiamine]mercury(II)
Dichloride (HgL2Cl2). A crystal of size 0.2 × 0.4 × 0.5 mm was
mounted in a glass capillary. Intensity data were collected with ω-scans,
using a variable scan speed (6.0-60.0° min-1 in ω) and a scan width
of 2.0°. A Simens P4/RA diffractometer with graphite-monochromated
Cu KR radiation was used for preliminary examination and data
collection. The lattice parameters were determined from a least-squares
fit of 55 reflections up to a maximum 2θ of 56°. Four standard
reflections were recorded every 1000 reflections, and only random
deviations were detected during data collection. A total of 3396
reflections with 4.0° < 2θ < 102.5°, -33 < h < 32, -1 < k <7, and
-21 < l < 19 was measured. The data were reduced and corrected
for Lorenz polarization effects and averaged (Rint ) 0.041) to 2508
unique reflections, 2149 of which had F > 4.0σ(F). The space group
was determined to be C2/c. The structure was solved via direct
methods. It was refined (on F) by using full-matrix least squares with
anisotropic displacement parameters for all non-hydrogen atoms and a
common isotropic displacement parameter for the H-atoms, which were
placed in geometrically calculated positions. A total of 289 parameters
was refined to R ) 0.049, wR ) 0.058, and (∆/σ)max ) 0.009. The
programs used were SHELX 76 (Sheldrick, 1976) and TEXSAN
(Molecular Structure Corporation, Version 1.6, 1993).
Various forms of the ligand were prepared by dissolving 100 mg in
aqueous solutions at pH 6, 3.5, and 1 by using 0.1 N solutions of KOH
or HCl. The solutions were then evaporated to dryness. To help
evaporation, small quantities of ethanol were added to the aqueous
solution of the ligand at pH 1. Solution proton undecoupled 31P NMR
spectra of the ligand at pH 1 indicate partial hydrolysis upon heating,
3
increasing with time (absence of the characteristic JP-H coupling
constant). This reaction was not investigated further at present. They
were dried first at room temperature and then at 55-60 °C in Vacuo.
Crystals of (LH)+Cl- were obtained by dissolving a small amount
of product in water (pH 3.5) in a small test tube and putting it in a
stoppered erlenmeyer flask containing ethanol. After diffusion of the
ethanol into the water solution at room temperature over several days,
crystals of (LH)+Cl- appeared in the test tube. The crystal structure
indicated that three molecules of water were also present per thiamine
unit cell.
2. Preparation of the MLCl2 Complexes (M ) Zn2+, Cd2+).
These complexes were prepared by mixing equimolar (1 mmol) amounts
of (LH)+Cl- and the metal chlorides (ZnCl2, CdCl2) in methanolic
solutions (20-30 mL). The pH meter was calibrated with aqueous
buffer solutions. Then 0.1 N KOH solution was added to both
methanolic solutions of the ligand and the metal chloride up to pH
5.5-6 (pH meter reading) and filtered from any insoluble material prior
to mixing. The resulting white precipitates, after the mixture was stirred
for about 2 h at room temperature, were filtered and washed with small
quantities of methanol and ether. They were then dried in Vacuo in
the presence of CaCl2 first at room temperature followed by heating to
50-60 °C. Elemental analysis suggested that three water molecules
were present per thiamine unit for both ZnLCl2 and CdLCl2 (yields ∼
50%).
3. Preparation of the M(LH)Cl3 Complexes (M ) Zn2+, Cd2+).
These were prepared as in the previous case by adjusting the pH to
about 3.5. The best agreement with elemental analysis was for a single
water molecule of crystallization to be present per thiamine unit (yields
∼ 50%).
(11) Louloudi, M.; Hadjiliadis, N.; Feng, J. A.; Sukumar, S.; Bau, R. J.
Am. Chem. Soc. 1990, 112, 7233.
(12) Louloudi, M.; Hadjiliadis, N.; Butler, I. S. J. Chem. Soc., Dalton Trans.
1992, 1401.
2. 13C and 31P CP/MAS NMR Spectra. Solid-state 31P NMR
spectra were acquired by using cross-polarization (CP), magic-angle
spinning (MAS), and high-power proton decoupling at 121.5 MHz on

Complexes of a Thiamine Monophosphate Chloride
Inorganic Chemistry, Vol. 35, No. 22, 1996 6515
Table 1. Summary of Crystal Data and Refinement Results for
(LH)+Cl-‚3H2O and HgL2Cl2‚H2O
acid. Following the proposal of Mason,15 the principal components
are given using the convention δ11 > δ22 > δ33, together with the span,
Ω, defined as δ11 - δ33, and the skew, κ, defined as 3(δ22 - δiso)/Ω.
To enable easy comparison with existing literature, values of the
anisotropy, ∆σ, and the asymmetry parameter, η, are also quoted: when
C19H30N4O8PSCl C38H46HgCl2N8O12P2S2
space group
a, Å
b, Å
Cc
C2/c
10.951(3)
17.579(4)
13.373(3)
105.36(2)
2482.4 (10)
4
32.968(6)
7.477(2)
21.471(4)
118.19(1)
4665(2)
4
δ11 - δ22 < δ22 - δ33, ∆σ ) 0.5(δ11 + δ22) - δ33 and η ) (δ22
-
δ11)/(δ33 - δiso); when δ11 - δ22 > δ22 - δ33, ∆σ ) 0.5(δ33 + δ22) -
δ11 and η ) (δ22 - δ33)/(δ11 - δiso).16 13C CP/MAS NMR spectra
were obtained by using the same conditions as described previously,
with chemical shifts quoted relative to TMS.12
c, Å
â, deg
V, Å3
molecules/unit cell
formula weight
cryst dimens, mm
calcd density, g cm-3
537.9
1204.4
3. Vibrational Spectroscopy. The IR spectra were obtained on a
Perkin-Elmer 783 instrument using either KBr disks or Nujol mulls.
The Raman spectra were obtained by using a Spex 1403 spectrometer
with a Spectra-Physics Model 2020 argon ion laser. Excitations were
performed with a wavelength of 514.5 mm.
4. Elemental Analyses. The elemental analyses of all forms of
ligands and the complexes were carried out in our laboratory by using
an EA-1108 Carlo Erba analyzer.
0.2 × 0.2 × 0.7
0.2 × 0.4 × 0.5
1.439
1.715
absorption coefficient (µ), 0.353
9.04
mm-1
data collectionn
wavelength, Å
2θmax, deg
0.7107
1.5418
45
4159
102.5
3396
total no. of reflections
measd
Results and Discussion
no. of independent
reflections
1832
2508
2149
Crystal Structures. Details of the crystal structure deter-
minations of (LH)+Cl- and HgL2Cl2 and relevant structural
information are given in Tables 1-4, and the structures are
shown in Figures 1 and 2. Both structures contain four
molecules per unit cell, and the water molecules present are
stabilized by a mixure of hydrogen bonds and electrostatic and
stacking interactions.
no. of reflections observed 1752
(F > 4.0σ(F))
no. of variable parameters 307
289
final agreement factors
R ) 0.035
wR ) 0.042
1.101
R ) 0.049
wR ) 0.058
1.209
GOF
scan type
scan speed, deg/min
ω
ω
variable
6.00-60.00 in ω
2.00
variable
6.00-60.00 in ω
2.00
The structure of the uncomplexed molecule (LH)+Cl-‚3H2O
shows no unexpected features. The molecule is in the so-called
S conformation, as has been found previously for other C(2)-
substituted thiamine derivatives.3 The torsional angles ΦT )
C5′-C3,5′-N3-C2 and ΦP ) N3-C3,5′-C5′-C4′ defining the
relative orientation of pyrimidine and thiazolium rings, are
104.1(5)° and 171.9(6)°, respectively.17 This is generally
attributed to an electrostatic interaction between S(1) and O(11)
accompanied by partial charge migration.3 The observed
scan range (ω), deg
a Brucker MSL-300 multinuclear spectrometer. Spinning rates of 1.8-
10 kHz were employed. The spectra obtained at the slow spinning
rates enabled the principal components of the 31P shielding tensor to
be obtained by simulation of the spinning sideband intensities using
an iterative fit procedure based on the method of Herzfeld and
Berger.13,14 The contact time used was 3 ms, and recycle delays were
2.5-15 s. Chemical shifts are relative to extermal 85% phosphoric
Table 2. Atomic Coordinates (×104) for C19H30N4O8PSCl and C38H46HgCl2N8O12P2S2
C19H30N4O8PSCl
C38H46HgCl2N8O12P2S2
x
y
z
x
y
z
Cl(1)
S(1)
P(1)
O(5δ)
O(5ꢀ)
O(5æ)
O(5γ)
C(5â)
C(5R)
C(5)
2415(1)
1501(1)
1781(1)
361(1)
-2479(1)
-2542(1)
173(1)
4270(1)
6624(1)
5641(1)
5242(1)
4721(1)
6414(1)
6136(1)
6725(1)
6779(1)
7316(1)
8341(1)
8560(1)
7732(1)
9178(1)
9607(1)
10335(1)
10044(1)
10747(1)
11767(1)
12117(1)
11412(1)
11779(1)
12529(1)
7731(1)
6663(1)
8315(1)
7942(1)
8495(1)
9390(1)
9764(1)
9226(1)
5781(1)
3350(1)
2840(1)
Hg(1)
Cl(1)
S(1)
0
457
-905(6)
191(4)
2500
-704(1)
2077(1)
2293(1)
2015(3)
1866(2)
2724(2)
2305(2)
2170(3)
3485(3)
242(3)
97(3)
660(3)
1656(3)
-34(4)
545(3)
2316(2)
4435(2)
2891(2)
5398(4)
2889(4)
3538(4)
2207(4)
2822(4)
3414(4)
3420(4)
4266(4)
5407(4)
4746(4)
3635(5)
4757(5)
4551(5)
3896(5)
3097(6)
5052(6)
4910(5)
3999(5)
4218(6)
3994(7)
5432(5)
5233(6)
5731(7)
5538(9)
4876(10)
4381(8)
4567(7)
3435(6)
2773(6)
152(1)
238(1)
784(1)
P(1)
-1408(4)
-1964(13)
-380(11)
-908(10)
-756(11)
-3329(10)
160(14)
2542(13)
4026(13)
4435(14)
2498(13)
3381(16)
3915(15)
3252(16)
2540(16)
3657(20)
3385(17)
879(17)
2197(15)
3309(16)
5184(17)
-381(18)
-797(15)
-463(20)
-807(22)
-1437(21)
-1765(19)
-1389(17)
2553(17)
1486(18)
2438(1)
2336(1)
2173(1)
3476(1)
3683(1)
2826(1)
2912(1)
1895(1)
1094(1)
3961(1)
1692(1)
2515(1)
3282(1)
4033(1)
4055(1)
3336(1)
2530(1)
1752(1)
4945(1)
-14(1)
-598(1)
488(1)
O(11)
O(5γ)
O(5δ)
O(5ꢀ)
O(5æ)
O(w)
N(1′)
N(3′)
N(4R′)
N(3)
C(2′)
C(4′)
C(5′)
C(6′)
C(2R′)
C(3,5′)
C(2)
-653(1)
-776(1)
-1635(1)
-2023(1)
-2035(1)
-2439(1)
-2754(1)
-1721(1)
-2450(1)
-3017(1)
-3535(1)
-4010(1)
-3948(1)
-3467(1)
-3015(1)
-2578(1)
-4445(1)
-3284(1)
-3408(1)
-4016(1)
-4483(1)
-5159(1)
-5348(1)
-4873(1)
-4204(1)
-3400(1)
-865(1)
-1348(1)
C(4)
N(3)
C(2)
C(4R)
C(3,5′)
C(5′)
C(6′)
N(1′)
C(2′)
N(3′)
C(4′)
N(4R′)
C(2R′)
C(10)
O(11)
C(1′′)
C(2′′)
C(3′′)
C(4′′)
C(5′′)
C(6′′)
Ow(3)
Ow(1)
Ow(2)
872(3)
693(3)
-526(4)
1382(3)
1816(3)
1962(3)
1734(3)
1588(4)
1786(4)
1286(4)
1138(4)
675(5)
384(5)
526(5)
986(4)
2095(4)
1811(4)
C(5)
C(4)
C(4R)
C(10)
C(1′′)
C(2′′)
C(3′′)
C(4′′)
C(5′′)
C(6′′)
C(5R)
C(5â)
1298(1)
1776(1)
1441(1)
636(1)
153(1)
4567(1)
1847(1)
-856(1)

6516 Inorganic Chemistry, Vol. 35, No. 22, 1996
Dodi et al.
Table 3. Bond Distances (Angstroms) in (LH)+Cl-‚3H2O and
HgL2Cl2‚H2O
Table 4. Selected Bond Angles (Degrees) of (LH)+Cl-‚3H2O and
HgL2Cl2‚H2O
bond
(LH)+Cl-‚3H2O
HgL2Cl2‚H2O
angle
(LH)+Cl-‚3H2O
HgL2Cl2‚H2O
Hg(1)-Cl(1)
Hg(1)-Cl(1A)
Hg(1)-N(1′)
Hg(1)-N(1′A)
P(1)-O(5γ)
P(1)-O(5ꢀ)
P(1)-O(5δ)
P(1)-O(5æ)
O(5γ)-C(5â)
C(5â)-C(5R)
C(5)-C(5R)
S(1)-C(5)
2.391
2.391
2.341
2.341
Cl(1)-Hg(1)-N(1′)
Cl(1)-Hg(1)-Cl(1A)
N(1′)-Hg(1)-Cl(1A)
N(1′)-Hg(1)-N(1′A)
C(2)-S(1)-C(5)
109.9(3)
129.6(2)
103.2(2)
96.5(5)
1.606(5)
1.585(8)
1.505(6)
1.503(5)
1.452(8)
1.526(9)
1.491(10)
1.756(7)
1.698(9)
1.338(8)
1.415(9)
1.482(8)
1.529(9)
1.419(8)
1.529(9)
1.393(11)
1.424(10)
1.382(12)
1.399(11)
1.406(9)
1.402(11)
1.475(10)
1.513(8)
1.363(9)
1.360(8)
1.361(10)
1.491(10)
1.323(9)
1.362(8)
1.334(9)
1.436(10)
1.600(9)
1.566(9)
1.492(6)
1.480(8)
1.414(15)
1.509(16)
1.494(21)
1.713(11)
1.694(13)
1.301(15)
1.414(17)
1.486(17)
1.503(18)
1.424(17)
1.525(17)
1.391(23)
1.404(23)
1.369(23)
1.369(31)
1.402(21)
1.372(15)
1.500(18)
1.511(13)
1.352(15)
1.348(12)
1.353(18)
1.496(14)
1.303(15)
1.353(11)
1.319(15)
1.432(19)
91.4(4)
105.2(3)
111.5(4)
116.9(3)
105.0(3)
110.3(3)
107.3(3)
118.3(4)
91.1(6)
O(5γ)-P(1)-O(5δ)
O(5δ)-P(1)-O(5ꢀ)
O(5δ)-P(1)-O(5æ)
O(5γ)-P(1)-O(5ꢀ)
O(5γ)-P(1)-O(5æ)
O(5ꢀ)-P(1)-O(5æ)
P(1)-O(5γ)-C(5â)
Hg(1)-N(1′)-C(2′)
Hg(1)-N(1′)-C(6′)
C(2′)-N(1′)-C(6′)
C(2′)-N(3′)-C(4′)
C(3,5′)-N(3)-C(2)
C(3,5′)-N(3)-C(4)
C(2)-N(3)-C(4)
N(1′)-C(2′)-N(3′)
N(3′)-C(4′)-C(5′)
C(4′)-C(5′)-C(6′)
C(4′)-C(5′)-C(3,5′)
C(6′)-C(5′)-C(3,5′)
N(1′)-C(6′)-C(5′)
N(3)-C(3,5′)-C(5′)
S(1)-C(2)-N(3)
109.4(5)
111.1(5)
115.6(4)
105.0(4)
105.5(5)
109.6(5)
121.0(9)
125.5(6)
116.9(8)
114.9(9)
119.4(11)
123.0(11)
122.6(9)
114.3(11)
125.4(9)
118.9(10)
115.8(9)
120.2(10)
123.9(12)
124.8(12)
110.9(9)
112.1(9)
119.4(9)
121.7(9)
111.5(10)
126.8(11)
112.3(11)
112.7(9)
105.0(11)
110.2(10)
S(1)-C(2)
C(2)-N(3)
N(3)-C(4)
119.4(6)
117.7(6)
123.3(6)
121.9(5)
114.6(6)
123.4(6)
121.7(6)
116.4(5)
119.4(6)
124.3(6)
121.2(6)
113.9(6)
111.4(5)
121.7(6)
121.4(5)
110.7(5)
127.5(6)
111.8(5)
106.6(5)
103.8(6)
113.0(5)
C(4)-C(4R)
C(2)-C(10)
C(10)-O(11)
C(10)-C(1′′)
C(1′′)-C(2′′)
C(2′′)-C(3′′)
C(3′′)-C(4′′)
C(4′′)-C(5′′)
C(5′′)-C(6′′)
C(6′′)-C(1′′)
N(3)-C(3,5′)
C(3,5′)-C(5′)
C(5′)-C(6′)
C(6′)-N(1′)
N(1′)-C(2′)
C(2′)-C(2R′)
C(2′)-N(3′)
N(3′)-C(4′)
C(4′)-N(4R′)
C(4′)-C(5′)
S(1)-C(2)-C(10)
S(1)-C(5)-C(5R)
S(1)-C(5)-C(4)
C(4)-C(5)-C(5R)
C(5)-C(5R)-C(5â)
O(5γ)-C(5â)-C(5R)
O(11)-C(10)-C(2)
O(11)-C(10)-C(1′′)
S(1)‚‚‚O(11) distance in (LH)+Cl- is 2.703(11) Å. There is a
stacking interaction between the aromatic rings of the pyrimidine
and the benzyl rings [average distance 3.113(9) Å]. The P(1)-
O(5γ) and P(1)-O(5ꢀ) bonds lengths are 1.606(5) and 1.585(8)
Å, respectively, indicating that there is probably an O(5ꢀ)-H
bond. By contrast, the P(1)-O(5æ) and P(1)-O(5δ) bonds are
significantly shorter at 1.503(5) and 1.505(6) Å, respectively,
implying that these are P-O (terminal) bonds and, thus, that
the phosphate group is in the monoanionic form.
A close examination of the structure of HgL2Cl2‚H2O reveals
a number of interesting features. In this complex, the coordina-
tion around the mercury atom is pseudotetrahedral with Hg-
Cl and Hg-N bond lengths of 2.391 and 2.341 Å, respectively,
and some deviations from the purely tetrahedral bond angle. A
crystallographic 2-fold rotation axis passes through the Hg atom.
It is noticeable that the Hg-Cl bond length is shorter and the
Hg-N bond length is longer than those in the related complex
Hg[2-(R-hydroxybenzyl)thiamine]Cl3.11 The C(2′)-N(1′)-
C(6′) bond angle of 114.9(9)° and the C(4′)-N(4R′) bond length
of 1.319(15) Å in HgL2Cl2 are smaller than those found in other
structures of protonated and metalated thiamine derivatives3
[e.g., compare 119.4(6)° and 1.334(9) Å for (LH)+Cl-]. These,
both angle and length, have previously been interpreted as being
functions of the Lewis acid strength of the bonded metal for
complexes of the type MLCl3,18 e.g., following the order Zn2+
< Cu+ < Cd2+ < Hg2+ < Pt2+ for the angle, but the smaller
Figure 1. Crystal structure of 2-(R-hydroxybenzyl)thiamine mono-
phosphate chloride [(LH)+Cl-‚3H2O].
Figure 2. Crystal structure of HgL2CL2.
(13) Herzfeld, J.; Berger, A. E. J. Chem. Phys. 1980, 73, 6021.
(14) Hawkes, G. E.; Sales, K. D.; Lian, L. Y.; Gobetto, R. Proc. R. Soc.
London A 1989, 424, 93.
angle and length here are probably simply a reflection of the
different stoichiometry.
(15) Mason, J. Solid State Nucl. Magn. Reson. 1993, 2, 285.
(16) Haeberlen, U. High Resolution NMR in Solids: Selective Averaging.
AdV. Magn. Reson. Suppl. 1976, 1, 9.
As in the case of (LH)+Cl-‚3H2O and other active aldehyde
(17) Pletcher, J.; Sax, M. J. Am. Chem. Soc. 1972, 94, 3998.
derivatives, the molecule is in the S conformation [ΦT )

Complexes of a Thiamine Monophosphate Chloride
Inorganic Chemistry, Vol. 35, No. 22, 1996 6517
Table 5. Principal Components of 31P, the Chemical Shift Tensor of 2-(R-Hydroxybenzyl)thiamine Monophosphate Chloride and Its
Complexes with Zn(II), Cd(II), and Hg(II)a,b
complex
pH
δiso
1.2
0.7
0.5(br)
0.3(w)
-2.3
-4.1
2.9(br)
1.7
0.0(w)c
-1.4(w)c
2.4
δ11
δ22
δ33
∆σ
η
Ω
K
L
6.0
3.5
6.0
3.5
75.2
72.4
57.6
59.9
68.6
65.6
60.1
68.3
13.0
11.2
-5.7
7.3
10.4
14.1
-0.9
11.7
-84.6
-81.5
-49.8
-67.9
-85.9
-92.0
-51.1
-74.9
128.7
123.3
-85.3
101.5
125.3
131.9
-86.1
114.9
0.73
0.74
0.78
0.78
0.70
0.5
160.0
153.8
107.4
127.8
154.4
157.7
111.2
143.2
0.22
0.21
-0.18
0.16
0.25
0.35
-0.10
0.21
(LH)+Cl-
ZnLCl2
Zn(LH)Cl3
CdLCl2
6.0
0.87
0.74
HgL2Cl2 (powder)
HgL2Cl2 (crystals)
6.0
6.0
61.0
59.6
14.9
15.9
-68.7
-67.9
106.7
105.6
0.65
0.62
129.7
127.5
0.29
0.32
2.4
a The chemical shifts are given in ppm relative to 85% H3PO4 using the convention δ11 > δ22 > δ33. The other parameters quoted are defined
in the Experimental Section. b The isotropic chemical shifts are accurate within 0.2 ppm, except for the peaks marked as broad (br) for which the
accuracy is within 1 ppm. The estimated uncertainties in the shielding tensor components are within (1.5 ppm for the strong narrow peaks, (3
ppm for ZnLCl2, and ( 6 ppm for the broad overlapped resonance in CdLCl2. c Weak peaks (w) were not simulated due to the extent of peak
overlap.
-98.1(9)°, ΦP ) 176.1(10)°]. As a consequence, the S(1)‚‚‚O(11)
distance is 2.711(14) Å, which is the shortest found thus far
for substituted thiamine complexes with divalent cations. This
is important as, according to Hogg,19 the S(1)‚‚‚O(11) electro-
static interaction is responsible for the O-H proton liberation
during the enzymatic process. As for (LH)+Cl-‚3H2O, there
is also a stacking interaction between the pyrimidine and benzyl
aromatic rings [average distance 3.371(13) Å]. The angle
between the pyrimidine and thiazolium planes in HgL2Cl2‚H2O
is 73.3(8)°, which again is smaller than that found for related
complexes [e.g., compare 80.4(6)° for (LH)+Cl-‚3H2O]. This
may be of importance as it has been suggested that those
complexes with smaller angles between these planes are more
susceptible to oxidation from thiamine to thiochrome.3
HgL2Cl2‚H2O contains two long P-O distances and two short
P-O distances with the latter attributed to P-O (terminal)
bonds, implying that, as in the case of (LH)+Cl-, the phosphate
group is in the monoanionic form (see Table 3).
Solid-State 31P NMR Spectroscopy. There have been a
number of studies correlating 31P chemical shift tensors with
structural parameters, and it is normally possible to distinguish
between monoanionic and dianionic phosphate environments
fairly easily on the basis of their anisotropy.20,21 Figure 3 shows
spectra of the uncomplexed phosphate ester and its zinc and
cadmium complexes. Both the full spinning sideband manifold
at slow spinning speeds and the isotropic peak region at fast
Figure 3. 31P CP/MAS NMR spectra of (a) L, pH 6; (b) ZnLCl2, pH
6; (c) Zn(LH)Cl3, pH 3.5; and (d) CdLCl2, pH 6. The spinning speeds
spinning speeds are shown. Analysis of the slow spinning speed
spectra gives the principal components of the 31P shielding tensor
reported in Table 5.
were 2-2.6 kHz for the slow spinning spectra (left-hand side) and 11.2
kHz for the fast spinning spectra (right-hand side; an expansion of only
the center band is shown).
The uncomplexed molecules L and (LH)+Cl- prepared at pH
6.0 and 3.5, respectively, give identical anisotropy parameters
within experimental error. The anisotropies observed (large
positive ∆σ values) are characteristic of monoanionic phosphate
enviroments.20-22 For instance, the monoanionic form of the
2′-phosphate group in NADPH has been found to have anisot-
ropy parameters ∆σ ) 130 ppm and η ) 0.56.22 This
assignment of the rate of the phosphate group is in agreement
with the interpretation of the P-O bond lengths derived from
the crystal structure discussed earlier.
for the uncomplexed molecule, the anisotropy parameters are
very different. This implies a difference in electronic shielding
at the 31P nucleus and so indicates a major change in the local
phosphorus environment. The negative values of ∆σ and κ
suggest that dianionic phosphate is present;20,22 however, the
asymmetry parameter, η, is rather higher than expected for a
dianionic phoshate environment. Thus, we believe that the 31
P
shielding tensor components provide clear evidence for direct
binding of the metal to the phosphate group. Literature values
of 31P shielding tensors of phosphates covalently bonded to
metals are not available to our knowledge.
A single peak, though rather broad, is observed for ZnLCl2.
While the isotropic chemical shift is similar to that observed
The zinc complex prepared at pH 3.5 [Zn(LH)Cl3] gives three
peaks in its31P NMR spectrum. Two major peaks are observed,
and these may well be due to crystallographically different
phosphorus sites in the same phase, while the third peak is weak
and so is probably just a minor impurity. Both of the major
peaks have shielding anisotropies comparable to that of the
(18) Cramer, R.; Maynard, R.; Evangelista, R. J. Am. Chem. Soc. 1984,
106, 111.
(19) Hogg, J. Bioorg. Chem. 1988, 10, 233.
(20) Olivieri, A. J. Magn. Reson. 1990, 88, 1.
(21) Un, S.; Klein, M. P. J. Am. Chem. Soc. 1989, 111, 5119.
(22) Gerothanassis, I. P.; Barrie, P. J.; Birdsall, B.; Feeney, J. Eur. J.
Biochem. 1994, 226, 211.

6518 Inorganic Chemistry, Vol. 35, No. 22, 1996
Dodi et al.
Table 6. Selection of Isotropic 13C Chemical Shifts of
2-(R-Hydroxybenzyl)thiamine Chloride, (LH)+Cl-, and Its
Complexes with Zn2+, Cd2, and Hg2+ (δ in ppm from TMS)
compound
(LH)+Cl-
L
ZnLCl2
CdLCl2
pH
C(2′)
C(6′)
C(5â)
3.5
6
6
162.1
163.2
167.3
166.3
164.4
164.1
161.9
162.6
162.6
167.1
129.7
128.6
130.5
130.3
130.5
130.3
129.7
129.6
129.8
131.6
63.6
63.1
65.1
64.9
67.2
67.1
67.5
67.3
67.3
65.9
6
Zn(LH)Cl3
Cd(LH)Cl3
(ZnCl4)2-(LH)2
3.5
3.5
1
1
1
+
+
(CdCl4)2-(LH)2
(HgCl4)2-(LH)2
HgL2Cl2
+
6
not been successful. It is, however, an indication of the power
of 31P solid-state NMR spectroscopy that such a prediction can
be made for these complexes in the absence of other data.
Solid-State 13C NMR Spectroscopy. 13C solid-state NMR
spectroscopy has developed into a routine complement to X-ray
crystallography, and it can, in favorable cases, distinguish
between different protonation and/or metalation states.
Chemical shifts of selected carbon atoms are included in Table
6. Assignments were based on comparisons with previous
results reported on complexes with 2-(R-hydroxybenzyl)-
thiamine12 and cross-polarization interrupted-decoupling experi-
ments.23
Comparison of the spectra of the ligand at pH’s 3.5
[(LH)+Cl-] and 6 (L) reveals that it is protonated at N1′ and
deprotonated at the phosphate group at pH 3.5 and deprotonated
at both sites at pH 6. Thus, the carbon atoms near N1′ of
(LH)+Cl-, i.e., C2′ and C6′, appear at 162.1 and 129.7 ppm,
respectively. For L, however, they shift downfield and upfield
by 1.1 ppm, respectively. The C5â atom near the phosphate
group, on the other hand, occurs at 63.6 ppm for (LH)+Cl- and
63.1 ppm for L, respectively. The ligand forms are presented
here:
Figure 4. 31P CP/MAS NMR spectra of (a) HgL2CL2, powdered sample
(spinning speed ) 2290 Hz) and (b) HgL2CL2 crystals as used in the
single-crystal X-ray structure determination (spinning speed ) 2030
Hz).
uncomplexed phosphate ester, thus clearly indicating that no
metal binding to the phosphate group occurs at this pH.
The cadmium complex, CdLCl2, prepared at pH 6 gives a
broad peak (ca. 58% of total area), a strong narrow peak (ca.
36%), and two weak narrow peaks. Analysis of the sidebands
from the broad peak gives tensor components similar to those
of ZnLCl2, in which direct metal-phosphate bonding was
deduced. On the other hand, the chemical shift tensor of the
strong narrow peak is similar to that of the uncomplexed
phosphate. Hence, this sample appears to be a mixure of two
phases: one with cadmium directly bonded to the phosphate
group and one with cadmium bonded elsewhere [probably the
N(1′) group of the pyrimidine ring].
Two samples of HgL2Cl2 were analyzed by 31P CP/MAS
NMR spectroscopy (see Figure 4). The first of these was a
polycrystalline powder prepared by precipitation from aqueous
solution, while the second was a batch of the crystals used in
the single-crystal X-ray structure determination (reported earlier
in this paper). In contrast to the situation for ZnLCl2 and
CdLCl2, both samples of HgL2Cl2 give a single sharp 31P
resonance. Analysis of the spinning sideband intensities
revealed that the two samples have identical tensor components,
as reported in Table 5. The shielding anisotropy parameters
are indicative of monoanionic phosphate and show little
difference from the uncomplexed molecule, indicating that
mercury does not bind directly to the phosphate group. This is
in agreement with the single-crystal X-ray structure determi-
nation discussed earlier, which showed that the mercury binds
only to the N(1′) group of the pyrimidine ring. Further, the
NMR results are indicative of phosphate in the monoanionic
form, which is in agreement with the fact that the crystal
structure shows P-O distances characteristic of two P-O
(terminal) bonds.
It is worth mentioning that the 31P NMR spectra and analyses
were in fact performed before suitable crystals of HgL2Cl2
became available for structure determination. The prediction
based on NMR results that mercury did not bind to the
phosphate group was subsequently confirmed by the crystal
structure. The prediction that metal phosphate bonding does
occur at pH 6 for the zinc complex and for one component of
the cadmium mixture prepared at pH 6 has not been confirmed
by crystallography, as attempts to prepare suitable crystals have
Addition of MCl2 (M ) Zn2+, Cd2+, Hg2+) to a freshly prepared
solution of the ligand at pH 1 results in the precipitation of the
+
corresponding (MCl4)2-(LH)2 complexes.

Complexes of a Thiamine Monophosphate Chloride
Inorganic Chemistry, Vol. 35, No. 22, 1996 6519
Table 7. Characteristic IR and Raman Bands (cm-1) of 2-(R-Hydroxybenzyl)thiamine Monophosphate Chloride, (LH)+Cl-, and Its Complexes
with Zn2+, Cd2+, and Hg2+
Raman
νPsO
IR
a
compound
(LH)+Cl-
L
pH
δNH2
νCdN
νMsCl
δNH2
νCdN
νPsO
νMsCl
3.5
6
6
3.5
1
6
3.5
1
1
1654, 1620
1599
1174
1675 (1185)
1670 (1185)
1655
1690, 1660 (1170)
1680 (1170)
1660
1688, 1660sh
1675 (1185)
1680 (1205)
1697 (1205)
1658
1610
1625
1620
1658
1622
1620
1660
1660
1620
1160
1130
1150
1200
1215
1155
1175
1215
1217
1158
ZnLCl2
1620
1602
1601
1601
1602
1600
1602
1601
1603
1160
1188
1188
1159
1181
1187
1187
1159
291
290m
320, 285
295
282
328, 285
255
Zn(LH)Cl3
(ZnCl4)2-(LH)2
CdLCl2
1660, 1624
1657, 1620
1630
1625
1660
1661
1618
323, 300, 290
338, 304
280, 262
283
259
262
+
+
Cd(LH)Cl3
(CdCl4)2-(LH)2
(HgCl4)2-(LH)2
HgL2Cl2
+
270, 255
270
6
277
a The numbers in parentheses are the δND2 vibrations.
Cd2+, Hg2+), and near 1620 cm-1 when it is metalated, also
following the order Hg2+ < Cd2+ < Zn2+ < H+, as in the case
of the same complexes with 2-(R-hydroxybenzyl)thiamine.11,27
For the complexes ZnLCl2 and CdLCl2, prepared at pH 6,
the C2′ shifts downfield by 3-4 ppm and the C6′ shifts by about
2 ppm, compared to the deprotonated ligand (L) at the same
pH. Also, the C5â atom adjacent to the phosphate group shifts
downfield by about 2 ppm, again compared to L. These results
strongly indicate simultaneous bonding of the metals at N1′ and
the phosphate group.
In the series Zn(LH)Cl3 and Cd(LH)Cl3, prepared at pH 3.5,
again C2′ and C6′ shift upfield by ∼1 ppm and downfield by
∼2 ppm, respectively, compared to L (Table 6), again implying
metalation at N1′. The chemical shift of the C5â atom near the
phosphate group, on the other hand, appears near 67.00 ppm.
These complexes therefore may have a zwitterionic structure
with the MCl3- moiety bonded to N1′ and the phosphate group
protonated.3,11,24
Evidence for the metalation or protonation of the phosphate
group, on the other hand, is given from the positions of the
νP-O bands, occurring at lower frequencies (1130-1160 cm-1
)
when it is deprotonated and metalated and at higher frequencies
(1175-1215 cm-1) when it is protonated.28 Similar behavior
is also observed for the band at the same range of frequencies
of the Raman spectra, again assigned to νP-O (see Table 7).
Finally, assignments for the νM-Cl bands are also included
in Table 7.
Conclusions
The binding sites of Zn2+, Cd2+, and Hg2+ in complexes with
2-(R-hydroxybenzyl)thiamine monophosphate chloride, (LH)+Cl-,
have been explored. Both the N(1′) site and the phosphate group
may be metal-binding sites of importance in determining the
enzymatic action of the ligand. The crystal structure of HgL2-
Cl2 indicates that the S conformation is adopted, with metal
binding solely to the N(1′) group of the pyrimidine ring. Metal
binding to the phosphate group is inferred from the 31P NMR
spectra of ZnLCl2 and one component of the CdLCl2 sample.
31P NMR spectra and the other techniques allow one to conclude
the protonation states of the phosphate group. In general, it
seems that 31P shielding tensors will be useful in characterizing
the binding of metal cations to the phosphate group in molecules
of biological interest.
The series (MCl4)2-(LH)2+, on the other hand, prepared at
pH 1, shows that C2′, C6′, and C5â chemical shifts comparable
to the protonated ligands may rather be ionic salts.4,25,26
Finally, in the complex HgL2Cl2 containing Hg-N1′ bonds
and a deprotonated monoanionic phosphate group, as was also
shown by the X-ray crystal structure, the C2′ appears at 167.1
ppm, shifted downfield by 3.9 ppm, and the C6′ appears at 131.6
ppm, shifted downfield by 3.00 ppm, compared to L.
Vibrational Spectroscopy. Bands that can be assigned to
δNH2 and νCdN of the pyrimidine ring and νPsO and νMsCl
of the ligand and the complexes, in the IR and Raman spectra,
are included in Table 7. In the region 1600-1700 cm-1 of the
IR spectra, both δNH2 and νCdN of pyrimidine are expected.
In fact, deuteration experiments have shown that the νCdN of
the pyrimidine ring of (LH)+Cl- occurs at 1658 cm-1, while
the δNH2 occurs at 1675 cm-1. The same frequencies appear
at 1610 and 1670 cm-1, respectively, for L (Table 7). The
νCdN band is shown near 1660 cm-1 whenever the N1′ is
Supporting Information Available: Tables of elemental analyses
of the complexes, anisotropic displacement coefficients, hydrogen atom
coordinates, electrostatic contacts and hydrogen-bonding interactions,
best weighted least-squares planes for pyrimidine, thiazole, and benzyl
rings, and various torsional angles for both (LH)+Cl-‚3H2O and HgL2-
Cl2‚H2O (16 pages). Ordering information is given on any current
masthead page.
protonated, i.e., (LH)+Cl- and (MCl4)2-(LH)+ (M ) Zn2+
,
2
(23) Xialing, W.; Shanmin, Z.; Xaewen, W. J. Magn. Reson. 1988, 77,
343.
(24) Hadjiliadis, N.; Markopoulos, J.; Pneumatikakis, G.; Katakis, D.;
Theophanides, T. Inorg. Chim. Acta 1977, 25, 21.
(25) Hadjiliadis, N.; Yannopoulos, A.; Bau, R. Inorg. Chim. Acta 1983,
69, 109.
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123.
IC950758X
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47A, 445.
(28) Khalil, V. J.; Brown, T. I. J. Am. Chem. Soc. 1964, 86, 5113.