Synthesis and crystal structure of coinage metal(I) complexes with tetrazole (Htetz) and triphenylphosphine ligands, and their antimicrobial activities. A helical polymer of silver(I) complex [Ag(tetz)(PPh3)2](n) and a monomeric gold(I) complex [Au(tetz)(PPh3)]

Article abstract of DOI:10.1016/S0020-1693(99)00401-6

Two novel coinage metal(I)-triphenylphosphine complexes with a heterocyclic ligand, [Ag(tetz)(PPh₃)₂](n) (1) and [Au(tetz)(PPh₃)] (2) (Htetz = tetrazole) were synthesized from a reaction in dichloromethane of the precursor complex [Ag(tetz)](n) with PPh₃ and from a reaction in acetone of [AuCl(PPh₃)] with Htetz in the presence of aqueous NaOH, respectively, and isolated as colorless needle crystals for both 1 and 2. The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction. These d¹⁰ complexes were also fully characterized by elemental analyses, TG/DTA and FT-IR in the solid-state, solution NMR (³¹P, ¹H and ¹³C, as well as ¹⁰⁹Ag for 1) spectroscopies and solution molecular weight measurements. Complex 1, is composed of a helical polymer, a 2₁ helix with a pitch 9.471 ?, formed by a bridged tetrazolate of an AgNP₂ core in the solid-state, but it was present as a monomer in solution. In contrast to 1, complex 2 consisted of a monomeric two-coordinate AuNP core without gold(I)-gold(I) interaction both in the solid-state and in solution. The molecular structures of 1 and 2 were compared with those of the corresponding triazole complexes, i.e. silver(I) complexes [Ag(1,2,3-triz)(PPh₃)₂](n) (3) and [Ag(1,2,4-triz)(PPh₃)₂](n) (4) both as helical polymers, a monomeric gold(I) complex [Au(1,2,3-triz)(PPh₃)] (5) and a dimeric gold(I) complex [Au(1,2,4-triz)(PPh₃)]₂ (6) through an intramolecular gold(I)-gold(I) bond; the structures of complexes 3-6 being recently determined by X-ray crystallography. The antimicrobial activities of 1, its precursor [Ag(tetz)](n) and 2 were compared and key factors affecting them discussed. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(99)00401-6

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 298 (2000) 24–32
Synthesis and crystal structure of coinage metal(I) complexes with
tetrazole (Htetz) and triphenylphosphine ligands, and their
antimicrobial activities. A helical polymer of silver(I) complex
[Ag(tetz)(PPh3)2]n and a monomeric gold(I) complex
[Au(tetz)(PPh3)]
Kenji Nomiya a,*, Ryusuke Noguchi a, Munehiro Oda b
a Department of Materials Science, Faculty of Science, Kanagawa Uni6ersity, Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan
b Meiji Cell Technology Center, Meiji Milk Products Co., Ltd., Odawara, Kanagawa 250-0862, Japan
Received 1 July 1999; accepted 28 July 1999
Abstract
Two novel coinage metal(I)-triphenylphosphine complexes with a heterocyclic ligand, [Ag(tetz)(PPh3)2]n (1) and [Au(tetz)(PPh3)]
(2) (Htetz=tetrazole) were synthesized from a reaction in dichloromethane of the precursor complex [Ag(tetz)]n with PPh3 and
from a reaction in acetone of [AuCl(PPh3)] with Htetz in the presence of aqueous NaOH, respectively, and isolated as colorless
needle crystals for both 1 and 2. The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction. These d10
complexes were also fully characterized by elemental analyses, TG/DTA and FT-IR in the solid-state, solution NMR (31P, 1H and
13C, as well as 109Ag for 1) spectroscopies and solution molecular weight measurements. Complex 1, is composed of a helical
,
polymer, a 21 helix with a pitch 9.471 A, formed by a bridged tetrazolate of an AgNP2 core in the solid-state, but it was present
as a monomer in solution. In contrast to 1, complex 2 consisted of a monomeric two-coordinate AuNP core without
gold(I)–gold(I) interaction both in the solid-state and in solution. The molecular structures of 1 and 2 were compared with those
of the corresponding triazole complexes, i.e. silver(I) complexes [Ag(1,2,3-triz)(PPh3)2]n (3) and [Ag(1,2,4-triz)(PPh3)2]n (4) both as
helical polymers, a monomeric gold(I) complex [Au(1,2,3-triz)(PPh3)] (5) and a dimeric gold(I) complex [Au(1,2,4-triz)(PPh3)]2 (6)
through an intramolecular gold(I)–gold(I) bond; the structures of complexes 3–6 being recently determined by X-ray crystallog-
raphy. The antimicrobial activities of 1, its precursor [Ag(tetz)]n and 2 were compared and key factors affecting them discussed.
© 2000 Elsevier Science S.A. All rights reserved.
Keywords: Tetrazole; Triphenylphosphine; Silver(I) complexes; Gold(I) complexes; Crystal structures
We have been interested in the structure-biological
activity correlation of the coinage metal complexes
[12–17].
1. Introduction
There is currently considerable interest in the coordi-
nation chemistry of coinage metals such as silver(I) and
gold(I) with biological or medicinal activities [1–11].
The molecular design and structural determination of
such silver(I) and gold(I) complexes composed of the
same ligands are an intriguing aspect of bioinorganic
chemistry, inorganic syntheses and metal-based drugs.
One recently highlighted topic in the coordination
chemistry of coinage metal(I) atoms is concerned with
the helicity (Table 1) [18–25], i.e. properties as helical
polymers of d10 metals, most of which have been re-
cently observed in silver(I) complexes, e.g. several sin-
gle-stranded helices such as [Ag(pydz)](NO3) (pydz=
pyridazine), [Ag(pydz)](OTf) (OTf=CF3SO3) and
[Ag(pydz)2](BF4) [18], [Ag(2,2%-biimidazole)](NO3) [23],
and the double helix of [Ag(bpp)](OTf) (bpp=1,3-
bis(4-pyridyl)propane) [22]. Chiral helical polymers
* Corresponding author. Tel.: +81-463-59 4111; fax: +81-463-58
9684.
E-mail address: nomiya@info.kanagawa-u.ac.jp (K. Nomiya)
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00401-6

K. Nomiya et al. / Inorganica Chimica Acta 298 (2000) 24–32
25
[Au(1,2,4-triz)(PPh3)]2 (6) [12], all of which have been
derived from reactions of the precursor [AuCl(PPh3)]
with N-heterocycles. In the dimeric complex 6, the
aurophilic interaction with gold(I)–gold(I) bond dis-
such as [Ag(S-Hpyrrld)]n (H2pyrrld=(S)-(−)-2-
pyrrolidone-5-carboxylic acid) [17], [Ag(R,R-DIOP)-
(NO3)]n (R,R-DIOP=(4R,5R)-trans-4,5-bis[(diphenyl-
phosphino)methyl]-2,2-dimethyl-1,3-dioxolane)
[20],
,
tance 3.1971(6) A has been found, whereas in the
and {[Ag(R,R-J)](OTf)}n (R,R-J=(4R,5R)-4,5-bis(2-(2-
pyridyl)ethyl)-1,3-dioxolane) [24], have been recently
found. Also, the double helical polymer in the gold(I)
complex has been elucidated for Cs2Na[Au2(tma)-
(Htma)] (myocrisine; H3tma=thiomalic acid) showing
antiarthritic action [25]. A second topic of interest is
the d10–d10 interaction between two closed shell
cations, or the aurophilic interaction, many examples
of which have been recently reported and reviewed
[26–33].
Transformation of polymeric silver(I) complexes
composed of N-heterocyclic ligands to their tertiary
phosphine derivatives has resulted in the formation of
monomers, oligomers, or helical polymers [14,16,34,35];
e.g. a reaction of a polymer [Ag(im)]n (Him=imida-
zole) with 3 equiv. of PPh3 gave a monomeric species
closely related gold(I) complex 5, it has not been
observed.
Thus, from a synthetic viewpoint, the helicity of the
PPh3 derivatives and the different reactivity of the
precursors have been found as significant differences in
the silver(I) and gold(I) complexes. In a viewpoint of
the biological activities, e.g. antimicrobial activities, the
polymeric silver(I) precursors [Ag(im)]n and [Ag(triz)]n
have shown wide spectra of antimicrobial activities
against bacteria, yeast and even mold, whereas their
PPh3 derivatives have shown poor activities [16]. On the
other hand, the antimicrobial test of the gold(I) com-
plexes has been scarcely reported.
In this work, we have examined synthesis and X-ray
crystallography of the silver(I) and gold(I) complexes
using another heterocyclic ligand, tetrazole (Htetz), in
the presence of auxiliary ligand PPh3. From a reaction
of the polymeric precursor [Ag(tetz)]n with 3 equiv. of
PPh3 in dichloromethane, light- and thermally-stable,
colorless needle crystals of [Ag(tetz)(PPh3)2]n (1) were
obtained in good yield. The analogous gold(I) complex
[Au(tetz)(PPh3)] (2) was obtained as colorless needle
crystals in good yield from a stoichiometric reaction of
the precursor [AuCl(PPh3)] with Htetz in acetone in the
presence of aqueous NaOH.
[Ag(im)(PPh3)3] [14,16],
a reaction of a polymer
[Ag(pz)]n (Hpz=pyrazole) with PPh3 formed the dinu-
clear [Ag2(pz)2(PPh3)2] and [Ag2(pz)2(PPh3)3] complexes
[34], and a reaction of polymers [Ag(1,2,3-triz)]n
(Htriz=triazole) and [Ag(1,2,4-triz)]n with 3 equiv. of
PPh3 provided single-stranded helical polymers
[Ag(1,2,3-triz)(PPh3)2]n (3) and [Ag(1,2,4-triz)(PPh3)2]n
(4) [13]. These PPh3 derivatives have never been isolated
from reactions of the precursors such as [AgCl(PPh3)3]
and [AgCl(PPh3)2]2 with N-heterocycles under alkaline
conditions. On the other hand, the corresponding
gold(I) complexes have been isolated as monomers or
dimers, but not as polymers, such as [Au(im)(PPh3)]
[14], [Au(pz)(PPh3)] [15], [Au(1,2,3-triz)(PPh3)] (5) and
Table 1
Comparison of silver(I) and gold(I) complexes with helical polymer structures
,
Complexes
Screw axis
A pitch of the helix (A)
Ref.
[Ag(pydz)](NO3)
[Ag(pydz)](CF3SO3)
[Ag(pydz)2](BF4)
[Ag(R,R-DIOP)(NO3)]n
{[Ag(R,R-J)](OTf)}n
[Ag(2,2%-biimidazole)](NO3)
[Ag(2,4%-bipy)]X (X=NO3−, ClO4−
{[Ag(bpp)](OTf)}n
[Ag(1,2,3-triz)(PPh3)2]n (3)
[Ag(1,2,4-triz)(PPh3)2]n (4)
21
21
41
21
21
3.68
5.40
11.166
[18]
[18]
[18]
[20]
[24]
[23]
[19]
[22]
[13]
[13]
[17]
a
16.186
a
c
c
c
31
c
)
double helix
21
21
21
double helix
21
21.1
9.12
9.53
a
[Ag(S-Hpyrrld)]n
Cs2Na[Au2(tma)(Htma)]
[Ag(tetz)(PPh3)2]n (1)
12.736
c
[25]
b
9.471
a Chiral helical polymer.
b This work.
c Not described.

26
K. Nomiya et al. / Inorganica Chimica Acta 298 (2000) 24–32
Herein, we report the full details of the synthesis,
solution were recorded at 25°C in 5 mm outer diameter
tubes on a Jeol JNM-EX 400 FT-NMR spectrometer
with a Jeol EX-400 NMR data processing system. H
crystallization and structural characterization of 1 and
2, as well as the results of their antimicrobial tests. Their
crystal structures were determined by single-crystal X-
ray diffraction. Complex 1 was a novel helical polymer,
a 21 helix, formed by a bridged tetrazolate of the AgNP2
core in the solid-state, while 2 consisted of a monomeric
two-coordinate AuNP core. In 2, no gold(I)–gold(I)
interaction was observed. Solution molecular weight
measurement revealed that complex 1 was a monomer
in solution. The compositional characterization of 1 and
2 was also performed by elemental analysis, ther-
mogravimetric and differential thermal analysis (TG/
DTA) and the structural characterization by FT-IR and
1
and 13C{1H} NMR spectra of the complex were mea-
sured in CDCl3 or CD2Cl2 solution with reference to an
internal TMS. Chemical shifts are reported on the l
scale and resonances downfield of TMS (l=0) are
recorded as positive. 31P{1H} NMR spectra were mea-
sured in CDCl3 or CD2Cl2 solution with reference to an
external standard of 25% H3PO4 in H2O in a sealed
capillary. Chemical shifts are reported as negative for
resonances upfield of H3PO4 (l=0).
109Ag NMR (18.45 MHz) were recorded at 25°C in
10 mm outer diameter tubes on a Jeol JNM-EX 400
FT-NMR spectrometer equipped with a Jeol NM-
40T10L low-frequency tunable probe. 109Ag NMR
spectra of the complexes were measured in CDCl3
solution with reference to an external standard of satu-
rated AgNO3–D2O solution by a substitution method.
Chemical shifts were recorded as positive for reso-
nances downfield of AgNO3 (l=0). Spectral parame-
ters for 109Ag NMR include: pulse width 13.2 ms;
acquisition time 0.390 s; recycle time 1.39 s; sweep width
21008 Hz.
1
solution NMR (31P, H and 13C, as well as 109Ag for 1).
The molecular structures of 1 and 2 were compared with
those of related silver(I) and gold(I) complexes 3–6, the
structures of which have been recently determined by
X-ray crystallography. Mention is also made of the
antimicrobial activities of complexes 1 and 2, and of the
precursor complex [Ag(tetz)]n, evaluated by MIC (mini-
mum inhibitory concentration).
2. Experimental
2.3. Syntheses
2.1. Materials and reagents
2.3.1. Preparation of precursor complex [Ag(tetz)]n
To a clear solution of 0.700 g (10.0 mmol) of tetrazole
in 20 ml water was added a colorless solution of 0.849
g (5.0 mmol) of AgNO3 dissolved in 10 ml water. To the
white suspension formed were added 5.0 ml of 1.0 M
aqueous NaOH (5.0 mmol), followed by stirring for 1 h.
White precipitates were collected on a Buchner funnel
(Whatman No. 5), washed twice each with 100 ml water,
100 ml ethanol and 100 ml acetone, and dried in vacuo
for 2 h. Colorless powder obtained in 0.85 g (95.9%)
yield was light-stable, insoluble in most solvents, and
explosive around 230°C when the sample is rapidly
heated, i.e. at a rate of 4°C min−1. (Note: no explosion
occurred on slow heating at a rate of 1°C min−1.) Anal.
Calc. for CHN4Ag or [Ag(tetz)] as a monomeric unit: C,
6.79; H, 0.57; N, 31.67. Found: C, 6.85; H, 0.64; N,
31.14%. TG/DTA data: no weight loss was observed
before decomposition temperature; decomposition be-
gan around 225°C with exothermic peaks at 225 and
361°C, which were observed at a rate of heating of 1°C
min−1. Some prominent IR bands at 1700–400 cm−1
region (KBr disc): 1636w, 1443w, 1430m, 1275m,
1180m, 1147s, 1120m, 1053w, 1010m, 995m, 892vs,
The following were used as received: tetrazole,
AgNO3, NaAuCl4·2H2O, NaOH, triphenylphosphine,
dichloromethane, ethanol, diethyl ether, hexane, light
petroleum (b.p.: 30–60°C), hexane, acetone, benzene
(all from Wako); CD2Cl2, CDCl3, D2O (Isotec).
[AuCl(PPh3)] was prepared according to literature meth-
ods [36–38]. Benzene should be used in a fume hood as
it is toxic.
2.2. Instrumentation/analytical procedures
CHNS elemental analyses were performed using a
Perkin–Elmer PE2400 series II CHNS/O analyzer.
Thermogravimetric (TG) and differential thermal analy-
sis (DTA) were carried out using a Rigaku TG 8101D
and TAS 300 data processing system. TG/DTA mea-
surements were run under air with a temperature ramp
of 1°C min−1 between 20 and 500°C. IR spectra were
recorded on a Jasco FT-IR 300 spectrometer in KBr
discs at room temperature (r.t.).
Molecular weight measurements in solution based on
the vaporimetric method using a vapor pressure os-
mometer were done by Mikroanalytishes Labor Pascher
(Remagen, Germany) and evaluated for 13.50 mg of
complex 1 dissolved in 1.1262 g of chloroform.
708vs cm−1
.
2.3.2. Preparation of [Ag(tetz)(PPh3)2]n (1)
1H NMR (399.65 MHz), 13C{1H} NMR (100.40
MHz) and 31P{1H} NMR (161.70 MHz) spectra in
[Ag(tetz)]n (0.177 g, 1.0 mmol) and 0.787 g (3.0 mmol)
of PPh3 were dissolved in 50 ml dichloromethane.

K. Nomiya et al. / Inorganica Chimica Acta 298 (2000) 24–32
27
After the solution was stirred for 1 h, it was filtered
through a folded filter paper (Whatman No. 2). The
clear colorless filtrate was added dropwise to 250 ml
diethyl ether. During 2 h-standing, colorless needle
crystals formed. They were collected on a membrane
filter (JG 0.2 mm), washed twice with 100 ml diethyl
ether, and dried in vacuo for 2 h. Light- and thermally-
stable, colorless needle crystals obtained in 0.68 g
(96.7%) yield were soluble in chloroform and dichloro-
methane, but insoluble in water, diethyl ether, light
petroleum and hexane. Anal. Calc. for C37H31N4P2Ag
or [Ag(tetz)(PPh3)2] as a monomer unit: C, 63.35; H,
4.45; N, 7.99. Found: C, 63.58; H, 4.50; N, 8.00%.
TG/DTA data: no weight loss was observed before
decomposition temperature; decomposition began
gradually around 229°C with an exothermic peak at
229°C. Molecular weight measurement: 710 in CHCl3;
calc. 701.5 for [Ag(tetz)(PPh3)2]. Some prominent IR
bands at 1700–400 cm−1 region (KBr disc): 1487m,
1434s, 1177w, 1128w, 1094m, 1073w, 1025w, 994w,
hexane and water. Anal. Calc. for C19H16N4PAu or
[Au(tetz)(PPh3)]: C, 43.20; H, 3.05; N, 10.60. Found: C,
43.46; H, 2.74; N, 10.30%. TG/DTA data: no weight loss
was observed below decomposition temperature; decom-
position began around 190°C with exothermic peaks at
190 and 433°C. Some prominent IR bands in the
1700–400 cm−1 region (KBr disc): 1478m, 1434vs,
1310w, 1179w, 1169w, 1150w, 1101vs, 1061m, 1021m,
997m, 968w, 745s, 711m, 691vs, 546vs, 511s, 499s cm−1
.
1H NMR (CD2Cl2, 25°C): l 7.54 (15H, m, aryl), 8.55
(1H, s, H5) ppm. 13C NMR (CD2Cl2, 25°C): l 128.4 (d,
JCP 64.3 Hz, phenyl), 129.9 (d, JCP 11.0 Hz, phenyl),
132.8 (s, phenyl), 134.7 (d, JCP 12.9 Hz, phenyl), 149.1
(C5) ppm. 31P NMR (CD2Cl2, 25°C): l 31.0 ppm.
2.4. X-ray crystallography
The two compounds [Ag(tetz)(PPh3)2]n (1) and
[Au(tetz)(PPh3)] (2) formed colorless, needle crystals by
a
slow evaporation in the solvent mixture of
742s, 694vs, 510m, 504m, 435w cm−1
.
1H NMR
dichloromethane–diethyl ether and by a vapor diffusion
with benzene/hexane as the internal/external solvent
system, respectively. Within one day’s standing of the
solutions at r.t., crystals of sufficient quality suitable for
single-crystal X-ray diffraction studies were grown.
Each of the single crystal 1 and 2 was mounted on
glass fiber and transferred to a Rigaku AFC5S diffrac-
tometer. Cell contents and orientation matrix of 1 and
2 were obtained from the least-squares refinement of 25
reflections. The reflection data were collected using
v–2q scan with graphite-monochromated Mo Ka radi-
ation at r.t. The intensities of three standard reflections
that were measured after every 150 reflections remained
constant throughout the data collection. The data were
corrected for Lorentz and polarization effects and em-
pirical absorption corrections based on PSI scan were
applied to the data. For the overall averaged transmis-
sion curve, the transmission factors of 1 and 2 were in
the range 0.924–0.999 and 0.688–1.000, respectively.
For complex 2, secondary extinction effects were cor-
rected to the data (coefficient 4.78850e-08). The struc-
tures were solved by direct methods followed by
subsequent difference Fourier calculation and refined by
a full-matrix least-squares procedure using the TEXSAN
package [39]. All non-hydrogen atoms were refined
anisotropically and hydrogen atoms isotropically.
Switching the position of C5/N2 in tetrazole produced
higher R and R% factors.
(CDCl3, 25°C): l 7.17 (30H, m, aryl), 8.07 (1H, s, H5)
ppm. 13C NMR (CDCl3, 25°C): l 128.8 (d, JCP 11.1 Hz,
phenyl), 129.9 (s, phenyl), 132.9 (d, JCP 20.2 Hz,
phenyl), 133.8 (d, JCP 16.6 Hz, phenyl), 150.5 (C5) ppm.
31P NMR (CDCl3, 25°C): l 7.23 ppm. 109Ag NMR
(CDCl3, 25°C): l 1036.5 ppm.
2.3.3. Preparation of [Au(tetz)(PPh3)] (2)
[AuCl(PPh3)] (0.495 g, 1.0 mmol) and 0.070 g (1.0
mmol) of tetrazole were dissolved in 80 ml acetone. To
this solution was added 1.0 ml of 1.0 M aqueous NaOH
(1.0 mmol). During 4 h stirring, white powder of NaCl
was produced and it was removed through a folded filter
paper (Whatman No. 2). The obtained colorless clear
filtrate was evaporated to dryness at 50°C with a rotary
evaporator. The residue was dissolved in 30 ml benzene,
followed by filtering through a folded filter paper (What-
man No. 2). The clear filtrate was added dropwise into
250 ml hexane. White precipitates formed, which were
collected on a membrane filter (JG 0.2 mm), washed with
light petroleum (2×20 ml) and dried in vacuo for 2 h.
Crystallization was performed by a vapor diffusion
method. The obtained white powder was redissolved in
10 ml benzene and the solution was filtered through a
folded filter paper (Whatman No. 2). The colorless
filtrate was used as an internal solution and hexane as
an external solvent for the vapor diffusion. After 6 h at
r.t., colorless needle crystals began to form. After 24 h,
the crystals were collected on a membrane filter (JG 0.2
mm), washed twice with 100 ml light petroleum, and
dried in vacuo for 2 h. Yield was 0.28 g (52.3%).
Relatively light- and thermally-stable, colorless needle
crystals obtained as compound 2 were soluble in ace-
tone, benzene, dichloromethane, chloroform and
DMSO, but insoluble in diethyl ether, light petroleum,
A summary of crystal data, data collection, and
refinement for 1 and 2 is given in Table 2.
2.5. Antimicrobial acti6ities
Antimicrobial activities of silver(I) and gold(I) com-
pounds were estimated by a minimum inhibitory concen-
tration (MIC: mg ml−1) as usual [13,14,16].

28
K. Nomiya et al. / Inorganica Chimica Acta 298 (2000) 24–32
Table 2
materials, the MIC of the test material was defined at
this point of dilution.
SCD, GP and PD media were purchased from
Nissui.
Summary of crystal data of the complexes [Ag(tetz)(PPh3)2]n (1) and
[Au(tetz)(PPh3)] (2) a,b
1
2
Formula
M
Crystal system
Space group
C37H31N4P2Ag
701.49
monoclinic
P21/n (no. 14)
14.587(2)
9.471(3)
24.653(2)
92.104(9)
3403(1)
1432
4
1.369
0.2×0.1×0.1
C19H16N4PAu
528.30
monoclinic
P21/c (no. 4)
9.650(3)
16.860(2)
11.866(4)
108.56(3)
1830.1(9)
1008
3. Results and discussion
3.1. Compositional characterization
,
a (A)
,
b (A)
,
c (A)
The molecular formulas of the precursor [Ag(tetz)]n
obtained as a white powder, [Ag(tetz)(PPh3)2]n (1) iso-
lated in 96.7% (0.68 g) yield as colorless needle crystals,
and [Au(tetz)(PPh3)] (2) isolated in 52.3% (0.28 g) as
colorless needle crystals, were consistent with all data of
i (°)
3
,
V (A )
F(000)
Z
4
Dcalc (g cm−3
)
1.917
0.3×0.1×0.1
25 (27.2–29.8)
the elemental analysis, TG/DTA, FT-IR and H, 13C
1
Crystal size (mm)
No. of reflections used for 25 (20.1–23.7)
unit cell dimension (2q
range (°))
and 31P NMR spectra presented in Section 2.3. In these
complexes, the IR measurements showed that the tetz
ligand coordinated to the metal(I) center as a tetrazo-
late anion, but not as a neutral tetrazole, because the
multiple vibrational bands due to NꢀH stretchings ob-
served in the free Htetz in the 3100–2600 cm−1 region
disappeared.
,
Radiation (u/A)
Mo Ka
Mo Ka
,
,
(u=0.71069 A)
(u=0.71069 A)
Scan mode
ꢀ–2q
ꢀ–2q
Scan width (°)
Scan speed (min−1
2q Range (°)
0.63+0.30 tan q
8
6–55
7.16
8606
8289
3915 (I\2.00|(I)) 2566 (I\2.00|(I))
0.044, 0.036
1.32
1.21+0.30 tan q
8
6–55
81.62
4559
4363
)
v (cm−1
)
From the single-crystal X-ray analysis described
later, the silver(I) and gold(I) compounds 1 and 2 are
shown to be polymer and monomer in the solid-state,
respectively.
On the other hand, molecular weight measurement in
CHCl3 solution revealed that complex 1 was present as
a monomeric species in solution. Although the gold(I)
complexes with an AuNP core have been present as
monomers and/or dimers in the solid-state, as observed
in 5 and 6, all of them are present as a monomer in
solution. It is possible that complex 2 is also present as
a monomer in solution.
Total reflections
Unique reflections
Observed reflections
R, R%
Goodness-of-fit
0.030, 0.019
1.24
a R=ꢀ[ꢁFoꢁ−ꢁFcꢁ]/ꢀꢁFoꢁ.
b R%=[ꢀ(w[ꢁFoꢁ−ꢁFcꢁ]2/[ꢀw(ꢁFoꢁ)2]1/2, with w=4Fo2/[|2(Fo2)].
Bacteria and yeast were inoculated into 5 ml of liquid
medium (SCD medium for bacteria and GP medium
for yeast), and cultured for 24 h at 35°C and 48 h at
30°C, respectively. The cultured fluids were adjusted to
the cell concentration of 106–107 ml−1 and used for
inoculation in the MIC test. As for the mold culture,
the agar slant (PD agar medium) for one week
cultivation at 27°C was washed with saline containing
0.05% Tween 80. The spore suspension obtained was
adjusted to the concentration of 106 ml−1 and used for
inoculation in the MIC test.
3.2. Crystal and molecular structures
Single crystals suitable for single-crystal X-ray analy-
sis were obtained for 1 and 2. The molecular structures
of 1 and 2 with the atom numbering scheme are de-
picted in Figs. 1 and 2, respectively. Selected bond
distances and angles with their estimated standard devi-
ations are listed in Table 3.
Complex 1 was a helical polymer, a 21 helix, consist-
ing of the AgI(PPh3)2 fragments bridged by tetrazolate
anions as shown in Fig. 1(a) and (b). The bond angles
around the silver(I) atom decrease in the order:
PꢀAgꢀP\PꢀAgꢀN\NꢀAgꢀN. The geometry of the
silver(I) atom is described as distorted tetrahedral coor-
dination. In complex 1, two PPh3 and two tetrazolates
coordinate to a silver(I) center via P1, P2, N1 and N3i
atoms. The N1i and N3 atoms coordinate to the adja-
cent silver(I) atoms (symmetry operation, (i) −x+3/2,
y−1/2, −z+3/2). Thus, the [Ag(tetz)(PPh3)2] moiety
is arranged helically along the b axis. The pitch of the
The test materials, [Ag(tetz)]n, [Ag(tetz)(PPh3)2]n (1),
[Au(tetz)(PPh3)] (2) and the free ligand, Htetz, were
added to each culture medium and then diluted two
times with each culture medium. Each one ml of culture
medium containing various concentrations of test
materials was inoculated with 0.1 ml of the
microorganism suspension prepared above.
Bacteria were cultured for 24 h at 35°C, yeast for 48
h at 30°C and mold were cultured for one week at
25°C, then the growth of microorganism was observed.
When no growth of microorganism was observed in the
medium containing the lowest concentration of test

K. Nomiya et al. / Inorganica Chimica Acta 298 (2000) 24–32
29
Fig. 1. (a) Molecular structure of the local coordination around each silver(I) center of [Ag(tetz)(PPh3)2]n (1) with 50% probability ellipsoids
(symmetry operations: (i) −x+3/2, y−1/2, −z+3/2; (ii) −x+3/2, y+1/2, −z+3/2); (b) top and (c) side views of the helical polymer
structure. In (c), black and small open circles represent nitrogen and carbon atoms, respectively.
The helical polymer 1, a 21 helix, can be compared
with several examples of infinite helical species of sil-
ver(I) and gold(I) complexes listed in Table 1.
helix, i.e. the distance between the silver(I) atoms of
,
Ag-tetz-Ag-tetz-Ag is 9.471 A (Fig. 1(c)). Among the
four nitrogen atoms of tetrazolate, N1 and N3 atomsfl
participate in the coordination. A single-stranded heli-
cal polymer of 1 has been accomplished with bridging
tetrazolates of the [Ag(PPh3)2] core. The formation of
this polymer is similar to that of [Ag(1,2,3-
triz)(PPh3)2]n (3) and [Ag(1,2,4-triz)(PPh3)2]n (4), both
21 helices.
The AgꢀP1 and AgꢀP2 distances are 2.441(1) and
,
2.456(1) A, respectively in complex 1. These distances
,
are longer than that of [Ag2(pz)2(PPh3)2] (2.376(1) A)
[34], and similar to those of [Ag(1,2,4-triz)(PPh3)2]n (4)
,
,
(2.441–2.469 A) [13], [AgCl(PPh3)2]2 (2.467–2.472 A)
,
[40] and [Ag2(pz)2(PPh3)3] (2.370–2.484 A) [34], but

30
K. Nomiya et al. / Inorganica Chimica Acta 298 (2000) 24–32
the Rietveld analysis using conventional X-ray powder
diffraction data [35], but similar to those of 3 (2.326–
,
,
2.327 A) [13] and of 4 (2.309–2.321 A) [13].
The neutral complex 2 was a discrete monomer con-
sisting of the AuN(PPh3) core coordinated by a tetrazo-
late anion, in which the geometry around the gold(I)
atom is described as almost linear coordination, the
PꢀAuꢀN angle being 178.4(1)°. Among the four nitro-
gen atoms of tetrazolate, only one N1 atom participates
in the coordination. As to the gold(I)–gold(I) interac-
tion observed in the recently reported complex
[Au(1,2,4-triz)(PPh3)]2 (6) [12], the possibility of stabi-
lization by a stacking interaction between one triazolate
ring and one of the phenyl rings in the PPh3 group has
been suggested. Thus, in 2, which contains a closely
related heterocyclic ligand, it should be noted that the
gold(I)–gold(I) interaction was absent.
The bond distances AuꢀN and AuꢀP (2.043(5) and
Fig. 2. Molecular structure of [Au(tetz)(PPh3)] (2) with 50% probabil-
ity ellipsoids.
,
2.239(2) A, respectively) in 2 are compared with those
of the reported neutral complexes, 5 (1.98(2) and
,
2.229(5) A) [12] and 6 (Au1ꢀN1a and Au2ꢀN1b
Table 3
,
2.026(7) and 2.037(7) A; Au1ꢀP1 and Au2ꢀP2 2.243(2)
,
Selected bond distances (A) and angles (°) for the complexes
,
and 2.238(2) A) [12], [Au(methym)(PPh3)] (Hmethym=
1-methylthymine) (AuꢀN and AuꢀP, 2.20(1) and
2.240(5) A) [42], [Au(mpyrid)(PPh3)] (Hmpyrid=6-
methylpyridone) (2.077(9) and 2.236(3) A) [43],
[Au(pyrmd)(PPh3)] (Hpyrmd=5-fluoro-1-(tetrahydro-
2-furanyl)-2,4(1H, 3H)-pyrimidinedione) (2.042(24) and
2.235(7) A) [44], [Au(theophyl)(PPh3)] (Htheophyl=
theophylline) (2.047(6) and 2.231(2) A) [45], and [Au(7-
[Ag(tetz)(PPh3)2]n (1) and [Au(tetz)(PPh3)] (2) a
,
1
2
,
AgꢀP1
AgꢀP2
AgꢀN1
AgꢀN3i
PꢀC
2.441(1)
2.456(1)
2.316(4)
2.337(4)
AuꢀP1
AuꢀN1
PꢀC
2.239(2)
2.043(5)
1.811−1.815
,
,
1.818−1.826
N1ꢀN2
N1ꢀC5
N2ꢀN3
N3ꢀN4
N4ꢀC5
1.339(7)
1.310(7)
1.342(8)
1.322(8)
1.298(8)
,
azaindolato)(PPh3)] (2.033(5) and 2.233(1) A) [46].
N1ꢀN2
N1ꢀC5
N2ꢀN3
N3ꢀN4
N4ꢀC5
1.336(6)
1.306(7)
1.297(6)
1.326(6)
1.316(7)
3.3. Solution NMR (31P, H and 13C) spectroscopies
1
The 31P NMR spectrum measured at r.t. in CDCl3 of
1 has shown only one resonance at l 7.23, the chemical
shift of which is in the region usually observed for the
PPh3 ligands coordinated to the silver(I) center and can
be compared with those of related silver(I) compounds:
l 3.71 for [Ag(im)(PPh3)3] [14], l 9.87 for
[Ag2(pz)2(PPh3)2] and l 6.13 for [Ag2(pz)2(PPh3)3] [34],
at l 6.48 for 3 and l 4.84 for 4 [13].
These resonances are observed in much higher field
than those of the coordinated PPh3 to the gold(I)
center. In fact, the 31P NMR spectrum of 2 in CD2Cl2
has shown one resonance for the PPh3 coordinated to
the gold(I) center at l 31.0, the chemical shift of which
is compared with those of related gold(I) complexes,
e.g. at l 32.46 for [Au(im)(PPh3)], at l 33.40 for
[AuCl(PPh3)] [14], at l 31.1 for 5 and at l 31.5 for 6
[12].
P1ꢀAgꢀP2
P1ꢀAgꢀN1
P1ꢀAgꢀN3
P2ꢀAgꢀN1
P2ꢀAgꢀN3
N1ꢀAgꢀN3
AgꢀN1ꢀN2
AgꢀN1ꢀC5
AgꢀN3ꢀN2
AgꢀN3ꢀN4
127.41(5)
107.0(1)
114.3(1)
107.4(1)
101.5(1)
94.3(2)
125.8(4)
129.7(4)
127.1(4)
119.3(4)
P1ꢀAuꢀN1
AuꢀN1ꢀN2
AuꢀN1ꢀC5
N1ꢀN2ꢀN3
N1ꢀC5ꢀN4
N2ꢀN1ꢀC5
N2ꢀN3ꢀN4
N3ꢀN4ꢀC5
178.4(1)
124.5(5)
129.0(5)
108.4(7)
110.1(6)
106.3(5)
106.4(6)
108.8(6)
at
a Symmetry operations: (i) −x+3/2, y−3/2, −x+3/2; (ii) −x+
3/2, y+1/2, −z+3/2.
shorter than those of [Ag(1,2,3-triz)(PPh3)2]n (3)
(2.460–2.512 A) [13], and [AgCl(PPh3)3] (2.520–2.556
,
i
,
A) [41]. The AgꢀN1 and AgꢀN3 distances of complex 1
1
,
are 2.316(4) and 2.337(4) A, respectively. These AgꢀN
The H NMR spectra measured at r.t. of 1 in CDCl3
distances are longer than those of [Ag2(pz)2(PPh3)2]
and 2 in CD2Cl2 exhibited only one resonance H5 of
the coordinating tetrazolate anion at l 8.07 and 8.55,
respectively, and the 13C NMR spectra showed only
one resonance C5 of the coordinating tetz− ligand at l
,
(2.204–2.213 A) [34], those of [Ag2(pz)2(PPh3)3] (2.176–
2.323 A) [34], and also those of [Ag(im)]n (2.05–2.08
,
,
A), the structure of which has been recently solved by

K. Nomiya et al. / Inorganica Chimica Acta 298 (2000) 24–32
31
Table 4
Antibacterial and antifungal activities of [Ag(tetz)]n, [Ag(tetz)(PPh3)2]n (1), [Au(tetz)(PPh3)] (2) and the free ligand Htetz, evaluated by MIC a
Htetz
[Ag(tetz)]n
[Ag(tetz)(PPh3)2]n (1)
[Au(tetz)(PPh3)] (2)
Escherichia coli
Bacillus subtilis
\1000
500
4
15.7
15.7
15.7
31.3
\1000
\1000
\1000
\1000
\1000
\1000
\1000
\1000
\1000
250
Staphylococcus aureus
Pseudomonas aeruginosa
Candida albicans
Saccharomyces cere6isiae
Aspergillus niger
\1000
\1000
\1000
\1000
\1000
\1000
500
\1000
\1000
\1000
\1000
\1000
15.7
\1000
\1000
Penicillium citrinum
a Minimum inhibitory concentration (MIC) (mg ml−1).
150.5 and 149.1, respectively. The 109Ag NMR spec-
trum measured at r.t. of 1 in CDCl3 showed only one
resonance at l 1036.5, which can be compared with
those of 3 and 4 in CDCl3 at r.t. at l 994 and 925,
respectively. The solution NMR (31P, 109Ag, 1H and
13C) spectra at r.t. of the previous silver(I) complexes
3 and 4, both of which are present as monomers
in solution, have been interpreted as averaged signals
resulting from the rapid dynamic exchange among sev-
eral unequivalent 109Ag species containing an ionic
species such as [Ag(PPh3)4]+(triz)− and [Ag(PPh3)2]+
(triz)− [13].
4. Conclusions
Transformation of polymeric silver(I) tetrazolate
[Ag(tetz)]n to its PPh3 derivatives resulted in the forma-
tion of a helical polymer [Ag(tetz)(PPh3)2]n (1), a 21
,
helix with a pitch 9.471 A, formed by a bridged tetrazo-
late of an AgNP2 core in the solid-state. The two
silver(I) triazolate complexes [Ag(1,2,3-triz)(PPh3)2]n (3)
and [Ag(1,2,4-triz)(PPh3)2]n (4) are helical polymers, a
,
pitch of helix being 9.12 and 9.53 A, respectively. On
the other hand, the gold(I) tetrazolate [Au(tetz)(PPh3)]
(2) was a discrete monomer with a two-coordinate
AuNP core without gold(I)–gold(I) interaction. The
two gold(I) triazolate complexes, [Au(1,2,3-triz)(PPh3)]
(5) and [Au(1,2,4-triz)(PPh3)]2 (6) are a monomer and a
dimer through a gold(I)–gold(I) interaction, respec-
tively. Thus, in comparison with anionic N-heterocyclic
ligands such as imidazolate, pyrazolate, and 1,2,3- and
1,2,4-triazolates, it is likely that the tetrazolate ligand in
1 acts similarly to the 1,2,4-triazolate, while that in 2
acts similarly to 1,2,3-triazolate. In contrast to the
precursor [Ag(tetz)]n complexes 1 and 2 did not show
effective antimicrobial activities. These facts can be also
utilized in the design of a new type of metal-based drug.
3.4. Antimicrobial acti6ities
Antimicrobial activities of the precursor [Ag(tetz)]n
and the two complexes 1 and 2 described here, together
with those of the free Htetz ligand are listed in Table 4,
as estimated by the minimum inhibitory concentration
(MIC, mg ml−1).
Antimicrobial activities of complex 1 were estimated
as \1000 mg ml−1 for bacteria, yeast and mold,
showing no activity. The free Htetz ligand and com-
plex 2 showed only poor activities against Gram-
positive bacteria (B. subtilis, S. aureus). On the other
hand, the precursor [Ag(tetz)]n has shown effective
activities against Gram-positive and negative bacteria,
and yeast, but no activities against mold. These facts
are consistent with the recently observed results;
the polymeric silver(I) complexes without a PPh3 lig-
and such as [Ag(im)]n [16], [Ag(1,2,3-triz)]n and
[Ag(1,2,4-triz)]n [13] have shown effective antimicrobial
activities, while almost all of their triphenylphosphine
derivatives such as [Ag(im)(PPh3)3], 3, and 4 have
shown no activity (\1000 mg ml−1). These facts have
been attributed to the restricted ligand exchange ability
of the AgꢀP bonding complexes [13,14,16]. From
a viewpoint of metal-based drug design, no activity
of the PPh3 derivatives is also crucial and can be
utilized.
5. Supplementary material
Supplementary crystallographic data sets for both
structures are available through the Cambridge Struc-
tural Data base. Copies of this information may be
obtained free of charge from The Director, CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK (fax: +44-
1223-336-033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
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