Syntheses, structures, and antimicrobial activities of light-stable and di- and mononuclear silver(I) carboxylate complexes composed of triphenylphosphine, and chiral and racemic forms of 2-pyrrolidone-5-carboxylic acid (H 2pyrrld). A variety of Ag-o bonding modes in the silver(I) complexes constructed with hard oxygen and soft phosphorus atoms

Article abstract of DOI:10.1246/bcsj.78.1953

Using light-stable dimeric silver(I) carboxylate precursors {[Ag(Hpyrrld)]₂}_n formed with chiral and racemic forms of 2-pyrrolidone-5-carboxylic acid (H₂pyrrld) ligand, six novel light-stable, triphenylphosphinesilver(I) complexes consisting of both a hard Lewis base (O atom) and a soft Lewis base (P atom) were prepared, i.e. [Ag ₂(R-Hpyrrld) ₂(H₂O)(PPh₃) ₂]·H₂O (1), [Ag(R-Hpyrrld)(PPh₃) ₂]₂ (2), [Ag₂(S-Hpyrrld)₂(H ₂O)(PPh₃)₂]·H₂O (3), [Ag(S-Hpyrrld)(PPh₃)₂]₂ (4), {[Ag(R,S-Hpyrrld)(PPh₃)]₂}_n (5), and [Ag(R,S-Hpyrrld)(PPh₃)₂] (6). Their solid-state and solution structures were unequivocally characterized with elemental analysis, TG/DTA, FTIR, X-ray structure analysis, molecular weight measurements in EtOH with the vaporimetric method, solution (¹H, ¹³C, and ³¹P) NMR, and solid-state ³¹P CPMASNMR spectroscopy. Two sets of the enantiomeric complexes were isolated as (1 and 3) and (2 and 4). X-ray crystallography revealed that these complexes possessed different Ag-O bonding modes, depending on the number of PPh₃ ligands and the chirality of the Hpyrrld^- ligand. The complexes 1-6 behaved as a monomeric species in EtOH and CD₂Cl₂. The antimicrobial activites by the silver(I) complexes in the water-suspension system against selected bacteria, yeast, and molds, were significantly correlated with the number of coordinating PPh₃ ligands per silver(I) atom in the complexes.

Full text of DOI:10.1246/bcsj.78.1953

ꢀ 2005 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 78, 1953–1962 (2005) 1953
Syntheses, Structures, and Antimicrobial Activities of Light-Stable
and Di- and Mononuclear Silver(I) Carboxylate Complexes Composed
of Triphenylphosphine, and Chiral and Racemic Forms
of 2-Pyrrolidone-5-carboxylic Acid (H2pyrrld). A Variety
of Ag–O Bonding Modes in the Silver(I) Complexes Constructed
with Hard Oxygen and Soft Phosphorus Atoms
ꢀ
Ryusuke Noguchi, Akiyoshi Sugie, Yohei Okamoto, Akihiro Hara, and Kenji Nomiya
Department of Materials Science, Faculty of Science, Kanagawa University, Tsuchiya, Hiratsuka 259-1293
Received March 22, 2005; E-mail: nomiya@chem.kanagawa-u.ac.jp
Using light-stable dimeric silver(I) carboxylate precursors {[Ag(Hpyrrld)]2}n formed with chiral and racemic
forms of 2-pyrrolidone-5-carboxylic acid (H2pyrrld) ligand, six novel light-stable, triphenylphosphinesilver(I) com-
plexes consisting of both a hard Lewis base (O atom) and a soft Lewis base (P atom) were prepared, i.e. [Ag2(R-
Hpyrrld)2(H2O)(PPh3)2] H2O (1), [Ag(R-Hpyrrld)(PPh3)2]2 (2), [Ag2(S-Hpyrrld)2(H2O)(PPh3)2] H2O (3), [Ag(S-
ꢁ
ꢁ
Hpyrrld)(PPh3)2]2 (4), {[Ag(R,S-Hpyrrld)(PPh3)]2}n (5), and [Ag(R,S-Hpyrrld)(PPh3)2] (6). Their solid-state and solu-
tion structures were unequivocally characterized with elemental analysis, TG/DTA, FTIR, X-ray structure analysis,
molecular weight measurements in EtOH with the vaporimetric method, solution (1H, 13C, and 31P) NMR, and solid-
state 31P CPMAS NMR spectroscopy. Two sets of the enantiomeric complexes were isolated as (1 and 3) and (2 and
4). X-ray crystallography revealed that these complexes possessed different Ag–O bonding modes, depending on the
number of PPh3 ligands and the chirality of the Hpyrrldꢂ ligand. The complexes 1–6 behaved as a monomeric species
in EtOH and CD2Cl2. The antimicrobial activites by the silver(I) complexes in the water–suspension system against
selected bacteria, yeast, and molds, were significantly correlated with the number of coordinating PPh3 ligands per
silver(I) atom in the complexes.
There is considerable interest in the coordination chemistry
of coinage metal (silver(I) and gold(I)) complexes with biolog-
ical and pharmacological activity. In bioinorganic chemistry of
coinage metal(I) complexes, there have been only a few bio-
logical and medicinal studies of silver(I) complexes, in com-
parison with many studies of gold(I) complexes related to their
antiarthritic,1 antitumor,1b,c,2 anti-HIV,1b,c and also, recently,
antimicrobial activities.3 The studies of silver(I) complexes
have been mostly related to their antiethylene4 and antimicro-
bial activities.5,6 The molecular design of such silver(I) and
gold(I) complexes are an intriguing aspect of the bioinorganic
chemistry of metal-based drugs.
In the past decade, the antimicrobial activities of Ag(I) and
Au(I) complexes have been actively studied.3,5,6 The anti-
microbial activities by metal complexes primarily depend on
the metal ions and, therefore, the different metal centers in
the complexes brought about the different activities. The in-
trinsic ease of ligand replacement of the Ag–O bonding com-
plexes due to low affinity between a hard Lewis base (oxygen
atom) and a soft Lewis acid (silver(I) atom) would permit a di-
rect interaction of such complexes with biological ligands, re-
sulting in the formation of silver(I)–biological ligand com-
plexes, i.e. growth inhibition of microorganisms. Thus, the an-
timicrobial activities by coinage metal complexes depend on
whether or not the complexes can possess further ligand-re-
placement ability with the biological ligands.6 It has been also
suggested6 that one of the key factors determining the antimi-
crobial effects of silver(I) complexes is the nature of the atom
coordinating to the silver(I) center and its bonding properties,
rather than the solubility, charge, chirality, or degree of poly-
merization of the complexes.
In relation to this concept, Ag–O bonding complexes, e.g.
silver(I) carboxylates, have attracted much attention as poten-
tial functional materials showing a wide spectrum of effective
antimicrobial activities. However, silver(I) carboxylates are, in
general, light-sensitive which, together with their poor solubil-
ity, makes structural characterization difficult.1a Recently, we
have prepared several water-soluble, light-stable chiral sil-
ver(I) carboxylates using chiral heterocyclic carboxylate li-
gands: {[Ag(Hpyrrld)]2}n (H2pyrrld = (S)-(ꢂ)- and (R)-(þ)-
2-pyrrolidone-5-carboxylic acid) (Chart 1),6a,b {[Ag(othf)]2}n
(Hothf = (S)-(þ)- and (R)-(ꢂ)-5-oxo-2-tetrahydrofurancar-
3
4
6
5
COOH
2
O
H
N
H
R-H pyrrld
2
Chart 1.
Published on the web October 31, 2005; DOI 10.1246/bcsj.78.1953

1954 Bull. Chem. Soc. Jpn., 78, No. 11 (2005)
Structures of Phosphinesilver(I) Carboxylates
petroleum (bp: 30–60 ꢃC) (all from Wako); CD2Cl2 (Isotec).
The silver(I) precursors, [Ag(R-Hpyrrld)]2, [Ag(S-Hpyrrld)]2,
and [Ag2(R-Hpyrrld)(S-Hpyrrld)], were prepared and identified
according to the literature.6a,b
boxylic acid),6c {[Ag(Hasp)]2}n (H2asp = D- and L-aspartic
acid),6d {[Ag2(ca)2]}n (Hca = camphanic acid (C10H14O4),
i.e. (1R,4S)- and (1S,4R)-4,7,7-trimethyl-3-oxo-2-oxabi-
cyclo[2.2.1]heptane-1-carboxylic acid), and {[Ag2(ca)2-
(Hca)2]}n.6e These complexes have shown a wide spectrum
of effective antimicrobial activities against bacteria, yeast,
and molds. Very recently, we have obtained the novel tetranu-
clear silver(I) cluster [Ag(2-Hmba)(PPh3)]4 with a three-leaves
propeller (C3 symmetry) in the 1:2:2 moler-ratio reaction of
[Ag2(R-Hpyrrld)(S-Hpyrrld)], PPh3, and 2-H2mba in a 1:4
mixed CHCl3/EtOH solvent.6f
Instrumentation/Analytical Procedures. The CHN analyses
were performed using Perkin-Elmer PE2400 series II CHNS/O
Analyzer (Kanagawa University). Infrared spectra were recorded
on a Jasco 4100 FT-IR spectrometer in KBr disks at room temper-
ature. Thermogravimetric (TG) and differential thermal analyses
(DTA) were acquired using a Rigaku TG8120 and Thermo Plus
2 system. TG/DTAꢃmeasurements were run under air with a tem-
ꢃ
perature ramp of 4 C per min between 20 and 500 C.
When a neutral donor ligand is incorporated in the silver
carboxylate coordination sphere, other structures can be antici-
pated as, for example, with phosphine or ammine ligands.1a
However, X-ray structure determination of silver(I) complexes
with both hard (anionic O-donor ligand) and soft Lewis bases
(e.g., PPh3 ligand) have been scarcely reported so far. Thus,
we have aimed at synthesizing the Ag(I)–O complexes with
different Ag–O bonding modes by incorporating the triphenyl-
phosphine ligand.
In this work, we have carried out the molar-ratio varied re-
actions of PPh3 and the three well-characterized Ag–O bond-
ing precursors, {[Ag(R-Hpyrrld)]2}n, {[Ag(S-Hpyrrld)]2}n,
and {[Ag2(R-Hpyrrld)(S-Hpyrrld)]}n, in 1:4 solvent mixture
of CH2Cl2 and EtOH. We have obtained six novel light-stable,
1H (399.65 MHz), 13C{1H} (100.40 MHz), and 31P{1H} NMR
(161.70 MHz) spectra in solution were recorded in 5-mm outer di-
ameter tubes on a JEOL JNM-EX 400 FT-NMR spectrometer
with a JEOL EX-400 NMR data processing system. 1H and
13C{1H} NMR spectra of the complexes were measured in
CD2Cl2 solution with reference to an internal TMS. Chemical
shifts are reported as positive for resonances downfield of TMS
(ꢀ0). 31P NMR spectra were referenced to an external standard
of 85% H3PO4 by a substitution method. Chemical shifts were
reported on the ꢀ scale with resonances upfield of H3PO4 (ꢀ0)
as negative. Solid-state 31P NMR (121.00 MHz) spectra were mea-
sured using a JEOL JNM-ECP 300 FT-NMR spectrometer equip-
ped with a cross-polarization (CP)/magic angle spinning (MAS)
accessory. The 31P CPMAS NMR spectra were referenced to an
external standard of (NH4)2HPO4 by a substitution method at
23.0 ꢃC and their chemical shifts were calibrated indirectly
through an external (NH4)2HPO4 (ꢀ0).
Molecular weight measurements in EtOH of complexes 1 and 2
with the vapor pressure osmometer were carried out by Mikroana-
lytishes Labor Pascher (Remagen, Germany) and evaluated for
15.69 mg of 1 dissolved in 0.3752 g of EtOH and 14.59 mg of
complex 2 dissolved in 0.3962 g of EtOH.
Antimicrobial Activitiy. Antimicrobial activities of silver(I)
complexes 1, 2, 5, and 6 were estimated by the minimum inhibi-
tory concentration (MIC: mg mLꢂ1) as shown elsewhere.6 The
antimicrobial tests of the water-soluble precursor [Ag(R-
Hpyrrld)]2 and ‘‘free ligand’’ R-H2pyrrld were carried out in a ho-
mogeneous aqueous media,6b while those of the organic-solvent
soluble complexes, 1, 2, 5, and 6 prepared here, were carried
out in a water–suspension system.
silver(I) complexes, i.e. [Ag2(R-Hpyrrld)2(H2O)(PPh3)2] H2O
(1), [Ag(R-Hpyrrld)(PPh3)2]2 (2), [Ag2(S-Hpyrrld)2(H2O)-
ꢁ
(PPh3)2] H2O (3), [Ag(S-Hpyrrld)(PPh3)2]2 (4), {[Ag(R,S-
ꢁ
Hpyrrld)(PPh3)]2}n (5), and [Ag(R,S-Hpyrrld)(PPh3)2] (6),
characterized them with elemental analysis, thermogravimet-
ric/differential thermal analysis (TG/DTA), FTIR, solution
(1H, 13C, and 31P) and solid-state 31P CPMAS NMR, molecular
weight measurements in EtOH, X-ray crystallography, and al-
so tested their antimicrobial activites against selected bacteria,
yeast, and molds in a water–suspension system. Complexes (1
and 3) and (2 and 4) are a set of enantiomers. X-ray crystallog-
raphy revealed that the Ag–O bonding modes in 1–6 were
quite different and strongly depended upon both chirality of
the Hpyrrldꢂ ligand and the number of the coordinating PPh3
ligands. The complexes 1–6 and the dimeric silver(I) precur-
sors were classified into four groups (Type I–IV) based on
the Ag–O bonding modes. In terms of reactivity of these com-
plexes, it was found the reaction from 1 and 3 formed the di-
meric meso-form 5, and that from 2 and 4 produced 6 as a
racemic compound. The behavior as a monomeric species in
EtOH and CD2Cl2 of 1–6 was also discussed based on molecu-
lar weight measurements in EtOH, 31P NMR in CD2Cl2, and
solid-state 31P NMR spectroscopy. Significant correlation be-
tween the antimicrobial activity and the number of coordinat-
ing PPh3 ligands per silver(I) atom was found.
[Ag (R-Hpyrrld) (H O)(PPh ) ] H O (1). To a suspension
2
2 Á
2
2
3
2
of 0.354 g (0.75 mmol) of [Ag(R-Hpyrrld)]2 dispersed in 10 mL of
1:4 (v/v) solvent mixture of CH2Cl2 and EtOH was added 0.262 g
(1.00 mmol) of PPh3. After stirring for 10 min, the white suspen-
sion was filtered off through a folded filter paper (Whatman #5).
By adding slowly 120 mL of light petroleum to the colorless clear
filtrate, two layers were formed. After a few days, colorless plate
crystals deposited, which were collected on a membrane filter (JG
0.2 mm), thoroughly dried by suction and dried in vacuo for 2 h.
Colorless plate crystals, obtained in 29.2% (0.151 g scale) yield,
were soluble in most organic solvents and insoluble in water
and light petroleum. Compound 1 was relatively unstable in solu-
tion: on standing the CH2Cl2 solution of 1 for a few days at room
temperature, it decomposed to give a solid of the original precur-
sor [Ag(R-Hpyrrld)]2, and compound 2 was formed in solution.
[Ag(R-Hpyrrld)(PPh3)2]2 (2). Compound 2 was prepared
by a 1:4 molar-ratio reaction in 10 mL of a solvent mixture
(CH2Cl2:EtOH = 1:4 (v/v)) of [Ag(R-Hpyrrld)]2 (0.236 g, 0.50
mmol) and PPh3 (0.525 g, 2.0 mmol). By the similar work-up de-
scribed above, colorless plate crystals of 2 were obtained in 53.0%
Herein, we report full details of the synthesis of complexes
1–6, their solution and solid-state characterization, the crystal
and molecular structures, classification (Type I–IV) of the
complexes based on the Ag–O bonding modes and their anti-
microbial activities.
Experimental
Materials. The following were reagent grade and used as
received: PPh3, EtOH, CH2Cl2, CHCl3, Et2O, acetone, and light

R. Noguchi et al.
Bull. Chem. Soc. Jpn., 78, No. 11 (2005) 1955
(0.403 g scale) yield, which were soluble in most organic solvents
and insoluble in water and light petroleum.
ing complex 5, except the use of 0.525 g (2.00 mmol) of PPh3,
was performed. Colorless cubic crystals, obtained in 44.0%
(0.670 g scale) yield, were soluble in DMSO, CH2Cl2, and CHCl3,
sparingly soluble in EtOH, and insoluble in water, light petroleum,
acetone, MeOH, EtOAc, acetonitrile, and Et2O. This complex in
solution was stable thermally and for light. The reaction product
was a racemic compound 6 of the monomeric, 4-coordinate
R- and S-complexes, which was identified with CHN analysis,
TG/DTA, FTIR, solution (1H, 13C, and 31P) NMR, and X-ray
crystallography.
X-ray Cystallography. Liquid–liquid diffusion consisting of
CH2Cl2/EtOH mixed solvent in the lower layer and light petrole-
um in the upper layer gave colorless plate crystals for 1–4 and col-
orless cubic crystals for 5 and 6. Crystals of sufficient quality suit-
able for single-crystal X-ray diffraction studies were grown.
Each single-crystal of silver(I) complexes 1–6 was mounted on
‘‘a loop’’ and used for measurements at 90 K of precise cell con-
stants, intensity data were collected on a Bruker Smart CCD dif-
[Ag (S-Hpyrrld) (H O)(PPh ) ] H O (3).
2
The precursor
2 Á
2
2
2
3
[Ag(S-Hpyrrld)]2 was used instead of [Ag(R-Hpyrrld)]2 in the
synthesis of 1. Colorless plate crystals of 3, soluble in most organ-
ic solvents and insoluble in water and light petroleum, were ob-
tained in 30.4% (0.157 g scale) yield.
[Ag(S-Hpyrrld)(PPh3)2]2 (4).
The precursor [Ag(S-
Hpyrrld)]2 was used in the place of [Ag(R-Hpyrrld)]2 in the syn-
thesis of 2. Colorless plate crystals of 4, soluble in most organic
solvents and insoluble in water and light petroleum, were obtained
in 69.9% (0.532 g scale) yield.
{[Ag(R,S-Hpyrrld)(PPh3)]2}n (5). In the preparation of 1, the
meso-form precursor [Ag2(R-Hpyrrld)(S-Hpyrrld)] (0.354 g, 0.75
mmol) dissolved in 15 mL of 1:4 (v/v) solvent mixture of CH2Cl2
and EtOH, and 0.262 g (1.00 mmol) of PPh3 were used. Colorless
clear cubic crystals of 5 were obtained in 25.9% (0.129 g scale)
yield, which were soluble in DMSO, CHCl3, and CH2Cl2, sparing-
ly soluble in EtOH, and insoluble in acetone, water, light petrole-
um, and Et2O.
ꢀ
fractometer (Mo Kꢁ radiation, ꢂ ¼ 0:71073 A). All calculations
for the subsequent structure determination were carried out using
the SHELXL (version 5.1).7 All non-hydrogen atoms were refined
anisotropically and hydrogen atoms isotropically. Crystal data,
data collection, and structure refinement of 1–6 are summarized
in Table 1.
Reaction from Complexes 1 and 3 Producing Complex 5.
[Ag2(R-Hpyrrld)2(H2O)(PPh3)2] (1)
þ [Ag2(S-Hpyrrld)2(H2O)(PPh3)2] (3)
Crystallographic data have been deposited at the CCDC, 12,
Union Road, Cambridge, CB2 1EZ, UK (Fax: +44 1223
336033; e-mail: deposit@ccdc.cam.ac.uk) and copies can be ob-
tained on request, free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, by quoting the publication citation and the
deposition numbers CCDC 259296-259301.
! 2/nf[Ag(R,S-Hpyrrld)(PPh3)]2gn (5):
ð1Þ
To a suspension of [Ag(R-Hpyrrld)]2 (0.236 g, 0.50 mmol) in 15
mL of a solvent mixture of CH2Cl2 and EtOH (1:4 (v/v)) was
added 0.262 g (1.00 mmol) of PPh3, followed by stirring for 30
min. In the solution, [Ag2(R-Hpyrrld)2(H2O)(PPh3)2] (1) is formed.
The 1:1 mixture of the in situ-generated complex 1 and its enan-
tiomer 3 in solution was prepared: to the clear colorless filtrate of
1 obtained by passing through a folded filter paper (Whatman #5)
was added the filtrate of the enantiomer 3. After stirring the mix-
ture for 1 h, the solution was passed through a folded filter paper
(Whatman #5). Along an interior wall of the beaker containing the
clear colorless filtrate was slowly spread 85 mL of light petrole-
um. The beaker containing the two phases composed of the filtrate
in the lower layer and the light petroleum in the upper layer was
sealed and placed in the dark. After one day, clear colorless cubic
crystals deposited, which were collected on a membrane filter
(JG 0.2 mm) and dried in vacuo for 2 h. Colorless cubic crystals,
obtained in 42.0% (0.418 g scale) yield, were soluble in DMSO,
CH2Cl2, and CHCl3, and insoluble in water, light petroleum, ace-
tone, MeOH, EtOH, EtOAc, acetonitrile, and Et2O. The product
was characterized and identified with CHN analysis, TG/DTA,
FTIR, solution (1H, 13C, and 31P) NMR, and X-ray crystallogra-
phy. The main product was complex 5, but it was contaminated
with a small amount of complex 6 with two PPh3 ligands.
[Ag(R,S-Hpyrrld)(PPh3)2] (6). In the place of the precursors
in the preparations of 2 and 4, the meso-form precursor [Ag2(R-
Hpyrrld)(S-Hpyrrld)] (0.236 g, 0.50 mmol) dissolved in 15 mL
of 1:4 (v/v) solvent mixture of CH2Cl2 and EtOH, and 0.525 g
(2.00 mmol) of PPh3 were used. Colorless cubic crystals of 6,
obtained in 53.8% (0.409 g scale) yield, were soluble in DMSO,
CHCl3, and CH2Cl2, sparingly soluble in EtOH, and insoluble
in acetone, water, light petroleum, and Et2O.
Results and Discussion
Compositional Characterization. The molecular formu-
las of silver(I) complexes 1–6 prepared here were consistent
with all data of elemental analysis, TG/DTA, FTIR, solid-state
31P CPMAS NMR, solution (1H, 13C, and 31P) NMR spectra,
all as listed in Table 2 and, also, X-ray structure analysis. Sil-
ver(I) complexes of 2, 4, 5, and 6 were isolated without any
solvent molecules. The presence of one solvated water mole-
cule and one water molecule bridged between two silver(I)
atoms in 1 and 3 was confirmed by elemental analysis, weight
loss observed in TG/DTA measurement, and X-ray crystallog-
raphy. The solid-state FT-IR spectra of 1–6 showed the multi-
ple vibrational bands based on the coordinating PPh3 ligands.
Upon complexation, the carbonyl stretching bands of the
‘‘free’’ ligand at 1720 and 1648 cmꢂ1 were shifted, which were
observed at 1656 and 1604 cmꢂ1 for 1 and 3, at 1679 and 1590
cmꢂ1 for 2 and 4, at 1665 and 1579 cmꢂ1 for 5, and at 1698
and 1589 cmꢂ1 for 6.
X-ray crystallography showed that 2 and 4 were discrete di-
mers, 1, 3, and 5 took supramolecular arrangements of the di-
meric units, and 6 was a racemic compound of two extremely
distorted 4-coordination monomers.
Crystal and Molecular Structures. The molecular struc-
tures of 1, 2, 5, and 6 with the atom numbering scheme are de-
picted in Figs. 1–4, respectively. Selected bond distances and
angles with their estimated standard deviations are listed in
Table 3.
Reaction from Complexes 2 and 4 Producing Complex 6.
[Ag(R-Hpyrrld)(PPh3)2]2 (2) þ [Ag(S-Hpyrrld)(PPh3)2]2 (4)
! 4[Ag(R,S-Hpyrrld)(PPh3)2] (6):
Similar work-up in the reaction from complexes 1 and 3 produc-
ð2Þ
The molecular structure (Fig. 1a) of the dinuclear complex 1
was composed of two silver(I) centers, two monoanionic

1956 Bull. Chem. Soc. Jpn., 78, No. 11 (2005)
Structures of Phosphinesilver(I) Carboxylates
Hpyrrldꢂ ligands, two PPh3 ligands, and one bridging water
molecule. In the crystal structure, one water molecule of crys-
tallization, which does not participate in the coordination, was
also found. A weak interaction between two silver(I) atoms in
ꢀ
1 was found (Ag–Ag distance 3.2854(7) A). The monodentate
PPh3 ligand was coordinated to the silver(I) center to form
a bended line of P1–Ag1 Ag1i–P1i (Ag1–P1 distance
ꢁꢁꢁ
i
2.3312(10) A, P1–Ag1–Ag1 angle 163.68(3)ꢃ, P1–Ag1
ꢀ
ꢁꢁꢁ
Ag1i–P1i dihedral angle 46.84(11)ꢃ). One (O3, O3i) of the
oxygen atoms in the carboxyl group in the Hpyrrldꢂ ligand
was bridged unsymmetrically between the two silver(I) centers
i
ꢀ
(Ag1–O3 distance 2.465(3) A and Ag1–O3 distance 2.341(3)
ꢀ
A). In the opposite site, the oxygen atom (O11) of the water
molecule was bridged symmetrically between the two silver(I)
ꢀ
centers (Ag1–O11 distance 2.438(3) A). Oxygen atoms (O1,
O1i) in the carbonyl group in the ligand were connected with
protons in the bridging water molecule in another molecular
ꢀ
unit to form a hydrogen bond (O1 O11 2.714 A). Thus, the
ꢁꢁꢁ
dimeric silver(I) complex 1 formed a supramolecular polymer
structure by intermolecular hydrogen-bonding interactions,
in which one coordinating water molecule plays a key role
(Fig. 1b).
In 2 as shown in Fig. 2, the two units of the 3-coordinate sil-
ver(I) moiety, i.e. an AgOP2 core, which consists of two PPh3
ligands and one carboxyl oxygen atom (Ag1–O3 2.3669(16)
ꢀ
A, Ag1–P1 2.4157(7) A, and Ag1–P2 2.4397(6) A), weakly
ꢀ
ꢀ
interacted intermolecularly between the silver(I) center and
i
ꢀ
the carbonyl O atom (Ag1 O4 2.628 A) to form a discrete
ꢁꢁꢁ
centrosymmetric dimer.
The molecular structure of 3 was a mirror image of 1. Dinu-
clear complex 3 was composed of two silver(I) centers with
ꢀ
the coordinating PPh3 ligand (Ag1–P1 2.340(3) A) and there
ꢀ
was a weak Ag–Ag interaction (3.294(3) A). One carboxyl
oxygen atom (O3, O3i) in the ligand was bridged unsymmetri-
cally between two silver(I) centers (Ag1–O3 distance 2.478(4)
i
ꢀ
A and Ag1–O3 distance 2.356(4) A). The oxygen atom (O11)
ꢀ
of one water molecule was bridged symmetrically between two
ꢀ
silver(I) centers (Ag1–O11 distance 2.450(4) A) and the two
protons participated in the hydrogen bonding interaction with
the carbonyl oxygen atom of the neighboring unit (O1 O11
ꢁꢁꢁ
ꢀ
2.726 A).
Complex 4 was a mirror image of 2. The two units of the
ꢀ
3-coordinate silver(I) moiety (Ag1–O3 2.443(3) A, Ag1–P1
ꢀ
2.425(2) A, and Ag1–P2 2.4748(16) A) with an AgOP2 core
ꢀ
consisting of two PPh3 ligands and one carboxyl oxygen atom
weakly interacted intermolecularly between the silver(I) center
i
ꢀ
and the carbonyl oxygen atom (Ag1 O4 2.628 A) to form a
ꢁꢁꢁ
discrete centrosymmetric dimer.
In 5 as shown in Fig. 3a, the two units of the 2-coordinate
silver(I) moiety with one PPh3 ligand and one carboxyl oxygen
ꢀ
atom (Ag1–O3 2.2071(18) A and Ag1–P1 2.3543(7) A) are
ꢀ
linked in a manner of head-to-tail binding between the sil-
i
ꢀ
ver(I) center and the carbonyl O atom (Ag1–O1 2.506(2) A)
to form a centrosymmetric dimer. Since the dimeric complex
5 contained both R- and S-forms of the Hpyrrldꢂ ligand in
the molecule, it is a meso-form. Furthermore, the dimeric com-
plex 5 in the solid state was supramolecularly arranged with
ii
ꢀ
van der Waals contact (Ag1 O3 2.641 A) as shown in Fig. 3b.
ꢁꢁꢁ
In 6 as shown in Fig. 4, the monomeric silver(I) complex

R. Noguchi et al.
Bull. Chem. Soc. Jpn., 78, No. 11 (2005) 1957
Table 2. Characterization Data of Silver(I) Complexes 1–6
Microanalysis
Found (Calcd)/%
1
3
5
(C46H46N2P2O8Ag2) C, 53.76 (53.51); H, 4.41 (4.49); N, 2.82 (2.71), 2 (C82H72N2P4O6Ag2) C, 64.69 (64.75); H, 4.82 (4.77); N, 2.07 (1.84)
(C46H46N2P2O8Ag2) C, 53.37 (53.51); H, 4.52 (4.49); N, 2.79 (2.71), 4 (C82H72N2P4O6Ag2) C, 64.58 (64.75); H, 4.64 (4.77); N, 2.17 (1.84)
(C46H42N2P2O6Ag2) C, 55.35 (55.44); H, 4.06 (4.25); N, 3.01 (2.81), 6 (C41H36NP2O3Ag)
C, 64.82 (64.75); H, 4.62 (4.77); N, 1.83 (1.84)
TG/DTA data
1
2
3
4
5
6
Weight loss of 3.6% was observed below 162 ꢃC (calcd for 2.0H2O, 3.4%). Endothermic peaks at 77 and 107 ꢃC. Exothermic peaks at 182, 251, and 269 ꢃC.
No weight loss before decomposition. Decomposition began around 193 ꢃC. Endothermic peak at 219 ꢃC. Exothermic peak at 268 ꢃC.
Weight loss of 3.8% was observed below 161 ꢃC (calcd for 2.0H2O, 3.4%). Endothermic peaks at 87 and 108 ꢃC. Exothermic peaks at 185, 259, and 281 ꢃC.
No weight loss before decomposition. Decomposition began around 192 ꢃC. Endothermic peak at 217 ꢃC. Exothermic peaks at 260 and 266 ꢃC.
No weight loss before decomposition. Decomposition began around 169 ꢃC. Exothermic peaks at 195, 267, and 286 ꢃC.
No weight loss before decomposition. Decomposition began around 204 ꢃC. Endothermic peak at 234 ꢃC. Exothermic peak at 262 ꢃC.
Results of molecular weight measurements in EtOH
546 (1014.5 for [Ag2(R-Hpyrrld)2(H2O)(PPh3)2])
Found (Calcd)
1
2
647 (1521.1 for [Ag(R-Hpyrrld)(PPh3)2])
Some prominent IR band at 1700–400 cmꢂ1 region (KBr)
1
2
3
4
5
6
1656vs, 1605s, 1481m (PPh3), 1461m, 1435s (PPh3), 1402m, 1384m, 1330w, 1274m, 1238m, 1158w, 1097m (PPh3), 1027w, 880w, 849w, 808w,
746m (PPh3), 696s (PPh3), 520m (PPh3), 500m (PPh3) cmꢂ1
1679vs, 1610m, 1590m, 1582m, 1478m (PPh3), 1434s (PPh3), 1393m, 1353m, 1300m, 1286m, 1254m, 1184w, 1155w, 1095m (PPh3), 1070w,
1026m, 998w, 969w, 920w, 877w, 855w, 795w, 743m (PPh3), 694s (PPh3), 510m (PPh3) cmꢂ1
1656vs, 1604s, 1481m (PPh3), 1461m, 1435s (PPh3), 1402m, 1384m, 1330w, 1274m, 1238m, 1159w, 1097m (PPh3), 1027w, 880w, 849w, 807w,
746m (PPh3), 696s (PPh3), 520m (PPh3), 500m (PPh3) cmꢂ1
1679vs, 1610m, 1590m, 1582m, 1479m (PPh3), 1434s (PPh3), 1393m, 1353m, 1300m, 1286m, 1254m, 1184w, 1155w, 1095m (PPh3), 1070w,
1026m, 998w, 969w, 920w, 877w, 854w, 795w, 743m (PPh3), 694s (PPh3), 510m (PPh3), 484s cmꢂ1
1665vs, 1579s, 1480m (PPh3), 1435m (PPh3), 1393m, 1283s, 1098m (PPh3), 1047w, 1027w, 997w, 926w, 878w, 748m (PPh3), 693m (PPh3), 620w,
545w, 521m (PPh3), 503m (PPh3) cmꢂ1
1698vs, 1589s, 1479m (PPh3), 1432m (PPh3), 1404m, 1298m, 1182w, 1157w, 1093m (PPh3), 1069w, 1026w, 997w, 974w, 923w, 802w, 746s (PPh3),
696vs (PPh3), 516m (PPh3), 504m (PPh3), 493m, 441w cmꢂ1
1H NMR
1
2
3
4
5
6
(CD2Cl2, 23.8 ꢃC)
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2.12–2.40 (4H, m, H3 and H4), 4.17 (1H, dd, H5), 7.00 (1H, s, NH), 7.39–7.50 (15H, m, Aryl).
1.89–2.33 (4H, m, H3 and H4), 4.01 (1H, dd, H5), 5.86 (1H, s, NH), 7.31–7.44 (30H, m, Aryl).
2.14–2.40 (4H, m, H3 and H4), 4.18 (1H, dd, H5), 6.94 (1H, s, NH), 7.39–7.51 (15H, m, Aryl).
1.93–2.32 (4H, m, H3 and H4), 4.00 (1H, dd, H5), 5.99 (1H, s, NH), 7.31–7.44 (30H, m, Aryl).
2.12–2.40 (4H, m, H3 and H4), 4.17 (1H, dd, H5), 6.97 (1H, s, NH), 7.39–7.51 (15H, m, Aryl).
1.89–2.33 (4H, m, H3 and H4), 4.00 (1H, dd, H5), 5.91 (1H, s, NH), 7.31–7.43 (30H, m, Aryl).
(CD2Cl2, 24.6 ꢃC)
(CD2Cl2, 23.6 ꢃC)
(CD2Cl2, 22.6 ꢃC)
(CD2Cl2, 24.4 ꢃC)
(CD2Cl2, 23.4 ꢃC)
13C NMR
1
2
3
4
5
6
(CD2Cl2, 23.4 ꢃC)
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
26.1 (C4), 30.8 (C3), 57.9 (C5), 129.3 (d, JCP ¼ 10:8 Hz, Ph), 131.1 (s, Ph), 131.1 (d, JCP ¼ 36:5 Hz, Ph),
134.2 (d, JCP ¼ 15:8 Hz, Ph), 178.6 (C6), 178.6 (C2).
(CD2Cl2, 23.5 ꢃC)
(CD2Cl2, 23.4 ꢃC)
(CD2Cl2, 26.1 ꢃC)
(CD2Cl2, 26.0 ꢃC)
(CD2Cl2, 24.6 ꢃC)
26.4 (C4), 30.9 (C3), 58.0 (C5), 129.3 (d, JCP ¼ 9:6 Hz, Ph), 130.8 (s, Ph), 132.6 (d, JCP ¼ 27:8 Hz, Ph),
134.3 (d, JCP ¼ 17:3 Hz, Ph), 177.7 (C6), 177.9 (C2).
26.4 (C4), 31.1 (C3), 58.1 (C5), 129.5 (d, JCP ¼ 10:0 Hz, Ph), 131.3 (s, Ph), 131.4 (d, JCP ¼ 35:7 Hz, Ph),
134.4 (d, JCP ¼ 16:6 Hz, Ph), 178.7 (C6), 178.8 (C2).
26.4 (C4), 30.9 (C3), 58.0 (C5), 129.3 (d, JCP ¼ 9:6 Hz, Ph), 130.7 (s, Ph), 132.7 (d, JCP ¼ 27:8 Hz, Ph),
134.3 (d, JCP ¼ 16:3 Hz, Ph), 177.7 (C6), 177.9 (C2).
26.2 (C4), 30.9 (C3), 57.9 (C5), 129.2 (d, JCP ¼ 10:8 Hz, Ph), 130.9 (s, Ph), 131.5 (d, JCP ¼ 34:0 Hz, Ph),
134.2 (d, JCP ¼ 16:6 Hz, Ph), 178.3 (C6), 178.4 (C2).
26.3 (C4), 30.8 (C3), 57.9 (C5), 129.1 (d, JCP ¼ 9:1 Hz, Ph), 130.5 (s, Ph), 132.5 (d, JCP ¼ 27:4 Hz, Ph),
134.1 (d, JCP ¼ 16:6 Hz, Ph), 177.4 (C6), 177.6 (C2).
31P NMR
1
5
(CD2Cl2, 22.9 ꢃC)
(CD2Cl2, 23.5 ꢃC)
ꢀ
ꢀ
15.2,
15.2,
2
6
(CD2Cl2, 23.5 ꢃC)
(CD2Cl2, 23.4 ꢃC)
ꢀ
ꢀ
9.7,
9.7,
3
(CD2Cl2, 22.9 ꢃC)
ꢀ
15.5,
4 ꢀ 9.7,
(CD2Cl2, 22.9 ꢃC)
Solid-state 31P CPMAS NMR (substitution method with (NH4)2HPO4, 23.0 ꢃC)
1
3
5
ꢀ
ꢀ
ꢀ
7.23 (JAg{P 699.7 Hz),
7.41 (JAg{P 684.8 Hz),
2
4
ꢀ
ꢀ
4.23 (JAg{P 669.9 Hz, JP{P 104.2 Hz), 8.70 (JAg{P 416.8 Hz, JP{P 104.2 Hz),
4.20 (JAg{P 662.5 Hz, JP{P 104.2 Hz), 8.67 (JAg{P 424.3 Hz, JP{P 104.2 Hz),
8.15 (JAg{P 699.7 Hz, JP{P 44.7 Hz),
6 ꢀ 4.84 (JAg{P 387.1 Hz, JP{P 148.9 Hz), 8.24 (JAg{P 439.2 Hz, JP{P 134.0 Hz)
ꢀ
with AgO2P2 core (Ag1–P1 2.436(3) A, Ag1–P2 2.432(2) A,
ꢀ
distorted tetrahedral geometry. The carbonyl oxygen atom
did not interact with any other groups. In the unit cell
(Z ¼ 2), a combination of one R-complex and one S-complex
was contained as a racemic compound.
ꢀ
ꢀ
Ag1–O2 2.529(7) A, Ag1–O3 2.399(7) A, Ag2–P3 2.441(3)
ꢀ
A, Ag2–P4 2.410(2) A, Ag2–O5 2.369(7) A, and Ag2–O6
ꢀ
ꢀ
ꢀ
2.508(8) A) was formed with a chelation by the two carboxyl
oxygen atoms and the two monodentate PPh3 ligands. The
bond angles around the silver(I) center, e.g. P1–Ag1–P2
125.79(9)ꢃ, O2–Ag1–O3 53.2(2)ꢃ, indicate an extraordinarily
Classification of the Ag–O Bonding Modes. Complexes
1–6 and the silver(I) precursors were classified to four types
(Type I–IV) based on the Ag–O bonding modes formed among

1958 Bull. Chem. Soc. Jpn., 78, No. 11 (2005)
Structures of Phosphinesilver(I) Carboxylates
(a)
Fig. 2. Molecular structure of the local coordination around
silver(I) center of [Ag(R-Hpyrrld)(PPh3)2]2 (2) with 50%
probability ellipsoids (symmetry operation i ¼ x þ 1, y, z).
and the number of coordinating PPh3 ligands.
Reactivities of Complexes. The reaction from 1 and 3 pro-
ducing the dimeric meso-form 5, which includes a ligand-ex-
change process, was confirmed. On the other hand, the racemi-
zation reaction from 2 and 4 producing 6 was also found. The
latter reaction does not include a ligand exchange process, but
only a change of the bridging Hpyrrldꢂ ligand between two sil-
ver(I) centers to the chelating ligand to the single silver(I)
atom. Interestingly, complex 2 or 4 alone did not show such
a chelation: in the presence of 4, the bridging Hpyrrldꢂ ligand
in 2 was changed to a chelated ligand, and in the presence of 2,
that in 4 was changed to a chelated ligand. Thus, complex 6 is
a racemic compound composed of a combination of R- and S-
complexes, both of which take an extraordinarily distorted tet-
rahedral geometry. Probably, this racemization reaction would
be caused in place of a formation of the unstable ‘‘meso’’ form
of dinulcear silver(I) complex with two PPh3 ligands.
These complexes (1, 5, and probably 3) were antimicro-
bially active, while complexes (2, 6, and probably 4) were in-
active, as described later.
(b)
1
Behavior in EtOH, (31P, H, and 13C) NMR in CD2Cl2,
and Solid-State 31P NMR Spectroscopy. Solution molecular
weight measurements of 1 (found 546; calcd 1014.5 for the
formula without hydrated water) and 2 (found 647; calcd
1521.1) in EtOH indicate that these complexes are present as
a monomeric species due to complete dissociation equilibrium.
If the dimeric complex 1 is dissociated by dissociation degree
ꢁ ¼ 1, several monomeric species containing EtOH coordina-
tion, e.g., ‘‘[Ag(R-Hpyrrld)(PPh3)(EtOH)n]’’ (FW 544.3 for
n ¼ 1; 590.4 for n ¼ 2) can be reasonably postulated in solu-
tion. On the other hand, for the dimeric complex 2, not only
the complete dissociation to the monomer ‘‘[Ag(R-Hpyrrld)-
(PPh3)2]’’ (FW 760.6), but also the dissociation of the PPh3 li-
gand to the species such as ‘‘[Ag(R-Hpyrrld)(PPh3)(EtOH)n]’’
should be also taken into account. If the complete dissociation
degree (ꢁ ¼ 1) to the monomer can be assumed, the dissocia-
tion degree of the PPh3 ligand can be evaluated as 0.176 from
the found and calculated molecular weights. Using these val-
ues, the distribution of dissociation species of 2 is estimated
Fig. 1. (a) Molecular structure of the local coordination
around silver(I) center of [Ag2(R-Hpyrrld)2(H2O)(PPh3)2]
(1) with 50% probability ellipsoids (symmetry operation
i ¼ x ꢂ y, ꢂy, ꢂz þ 1=3), and (b) side view of the poly-
mer chains extended along the crystallographic a axis.
the silver center, and the carboxyl and/or carbonyl as shown
in Fig. 5. Complexes belonging to the Type I are formed by
monodentate coordination of the single oxygen atoms to the
silver(I) center as observed in 2, 4, and 5, that in the Type II
is formed by a chelate formation of the two carboxyl oxygen
atoms as observed in 6, those in the Type III are formed by
bridging of the single oxygen atoms between two silver(I) cen-
ters as observed in 1 and 3, and those in the Type IV are ob-
tained by bis(carboxylato-O,O0)-bridged dimer (Ag2O4 core)
formation as observed in the precursors without PPh3 ligand.
The Ag–O bonding modes in 1–6 were quite different, which
strongly depended upon both chirality of the Hpyrrldꢂ ligand

R. Noguchi et al.
Bull. Chem. Soc. Jpn., 78, No. 11 (2005) 1959
Fig. 4. Molecular structure of the local coordination around
silver(I) center of [Ag(R,S-Hpyrrld)(PPh3)2] (6) with 50%
probability ellipsoids. In the unit cell, a racemic mixture
of the enantiomeric complexes was found.
O
P
Ag
O
O
Ag
O
O
P
(a)
Type III
O
Ag
complex 1 or 3
O
O
O
O
P
Ag
[Ag(R- (orS-)Hpyrrld)]
O
O
Ag
O
P
2
Type I
Type I
Type II
complex 2 or 4
Type IV
O
O
O
Ag
O
P
O
Ag
O
O
complex 5
O
O
Ag
O
P
P
O
Ag
O
[Ag(R,S-Hpyrrld)]
2
complex 6
Fig. 5. Classification (Type I–IV) of the precursor
[Ag(Hpyrrld)]2 and complexes 1–6 based on the Ag–O
bonding modes among the silver center, and the carboxyl
and/or carbonyl oxygen atoms.
(b)
Fig. 3. (a) Molecular structure of the local coordination
around silver(I) center of {[Ag(R,S-Hpyrrld)(PPh3)]2}n
(5) with 50% probability ellipsoids (symmetry operation
i ¼ ꢂx þ 1, ꢂy, ꢂz; ii ¼ ꢂx þ 2, ꢂy, ꢂz). The dimeric
complex is a meso-form with both one R- and one S-
Hpyrrldꢂ ligands in the molecule. (b) Side view of the
polymer chains extended along the crystallographic a axis.
CD2Cl2 should be understood based on the monomeric spe-
cies. This is the case for complexes 5 and 6.
The 31P NMR spectra in CD2Cl2 (Table 2) showed only one
resonance at around ꢀ 15.2 for silver(I) complexes (1, 3, and 5)
with one PPh3 ligand per silver(I) atom and only one reso-
nance at around ꢀ 9.7 for silver(I) complexes (2, 4, and 6) with
two PPh3 ligands per silver(I) atom. Since no 31P signal of the
free PPh3 (ꢂ5:33 ppm) ligand is observed in the 31P NMR
spectra of 2, 4, and 6 at room temperature in CD2Cl2, the ob-
served spectra should result from a rapid dynamic exchange of
the free PPh3 ligands as dissociation species. In CD2Cl2 solu-
tion, the dimeric complex 5 with meso-form is changed to a
racemic mixture of monomeric R- and S-complexes with one
PPh3 ligand per silver(I) atom. Solution 31P NMR also indi-
cates that the racemic compound 6 in the solid state will be
to be the monomeric silver(I) species having two PPh3 ligands
(70.0%), the species having one PPh3 ligand (15.0%), and free
PPh3 (15.0%).
Thus, the molecular formulas and molecular structures of 1–
4 are valid only in the solid state. Although the solvent used
for NMR measurements is different from that of molecular
weight measurements, solution (31P, 1H, and 13C) NMR in

1960 Bull. Chem. Soc. Jpn., 78, No. 11 (2005)
Structures of Phosphinesilver(I) Carboxylates
present as a racemic mixture of the monomeric complexes
with a very similar geometry to those of 2 and 4 in solution,
which would contain the monodentate coordination of the
Hpyrrldꢂ ligand, but not the chelation. The resonances in com-
plexes 1–6 were observed in much higher field than that of
one coordinating PPh3 to the gold(I) center (ꢀ 28.0 for
[Au(R,S-Hpyrrld)(PPh3)],6g ꢀ 29.4 for [Au(O2CNEt2)(PPh3)]8
ꢂ
(O2CNEt2 = N,N0-diethylcarbamato)).
The solid-state 31P CPMAS NMR spectra of 1–6 (Table 2),
which were quite different from the solution 31P NMR spectra,
showed signals of the PPh3 ligand coordinating to the silver(I)
atom as doublet peaks (two lines) for 1 and 3, as two double
doublet peaks (six lines) for 2, 4, and 6 and as double doublet
peaks (four lines) for 5. These splitting peaks are due to
1J(Ag–P) and 2J(P–P) couplings,9 and these results are consis-
tent with the solid-state structures revealed by X-ray crystal-
lography.
1
The H NMR spectra of 1–6 in CD2Cl2 (Table 2) showed
signals of the coordinating Hpyrrldꢂ ligands as multiplet peaks
for the two methylene groups (H4 and H3), as single peak for
the NH proton and as double doublet peaks (four lines) for the
H5 proton within the ring. The 13C NMR spectra of 1–6 in
CD2Cl2 (Table 2) showed signals of the coordinating Hpyrrldꢂ
ligands as single peaks for C4, C3, C5, C6, and C2.
Antimicrobial Activities. Antimicrobial activities estimat-
ed as the minimum inhibitory concentration (MIC, mg mLꢂ1
for complexes 1, 2, 5, and 6 are listed in Table 4.
)
Antimicrobial activites of ‘‘free ligand’’ H2pyrrld were esti-
mated as >1000 mg mLꢂ1 for tested bacteria, yeast, and molds,
showing no activity.6b The precursor without PPh3 ligand,
[Ag(R-Hpyrrld)]2, showed a wide spectrum of remarkable
and excellent activities against selected Gram-negative (E. coli
and P. aeruginosa) and -positive bacteria (B. subtilis and
S. aureus) and yeast (C. albicans and S. cerevisiae), and even
against two tested molds (A. niger and P. citrinum).6b The
enantiomeric complex [Ag(S-Hpyrrld)]2 has also shown very
similar antimicrobial spectrum and activities, suggesting that
the chirality of the complexes does not affect the antimicrobial
activities.6a
Complex 1 with one PPh3 ligand per silver(I) atom showed
a relatively wide spectrum with effective activities against bac-
teria and yeast. Complex 1 also showed activity against one
(P. citrinum) of two tested molds. Complex 5 with one PPh3
ligand per silver(I) atom also showed effective activities
against Gram-negative (E. coli) and -positive bacteria (B. sub-
tilis and S. aureus) and yeast (C. albicans and S. cerevisiae),
and even against two tested molds (A. niger and P. citrinum).
On the other hand, complexes 2 and 6 with two PPh3 ligands
per silver(I) atom showed no activity against all microorgan-
isms tested. Complexes 1 and 3 which showed a ligand-ex-
change process, and the resulting, still labile complex 5 were
antimicrobially active, whereas complexes 2 and 4 which did
not show the ligand-exchange process and the inert complex
6 were antimicrobially inactive. These aspects are consistent
with the previously reported conclusions.6
The antimicrobial activities observed here were significantly
correlated with the number of soft PPh3 ligands per silver(I)
atom contained in the complexes and, therefore, with the
resulting Ag–O bonding modes.

R. Noguchi et al.
Bull. Chem. Soc. Jpn., 78, No. 11 (2005) 1961
Table 4. Antimicrobial Activities of Silver(I) Complexes 1–6, [Ag(R-Hpyrrld)]2 and ‘‘Free’’ Ligand Evaluated
by Minimum Inhibitory Concentration (MIC/mg mLꢂ1
)
aÞ
[Ag(R-Hpyrrld)]2
R-H2pyrrldaÞ
1
2
5
6
Escherichia coli
Bacillus subtilis
Staphylococcus aureus
Pseudomonas aeruginosa
Candida albicans
>1000
>1000
>1000
>1000
>1000
62.5 >1000
62.5 >1000
125
500
125
>1000 15.7
>1000 31.3
>1000 31.3
>1000 15.7
125
>1000
250
500
>1000 1000
>1000
62.5 >1000
62.5 >1000 15.7
250
250
7.9
Saccharomyces cerevisiae >1000
>1000
>1000
500
>1000
250
>1000
>1000
>1000
Aspergillus niger
Penicillium citrinum
>1000 15.7
>1000 15.7
a) Ref. 6b.
Conclusion
References
1
a) M. C. Gimeno and A. Laguna, ‘‘Comprehensive Coordi-
The crystal and molecular structures of six chiral or racemic
triphenylphosphinesilver(I) carboxylate complexes, [Ag2(R-
nation Chemistry II,’’ Elsevier, Oxford (2004), Vol. 6, p. 911. b)
C. F. Shaw, III, Chem. Rev., 99, 2589 (1999). c) C. F. Shaw,
III, ‘‘Uses of Inorganic Chemistry in Medicine,’’ ed by N. P.
Farrell, RSC, U. K. (1999), Chap. 3, p. 26. d) W. Kaim and B.
Schwederski, ‘‘Bioinorganic Chemistry: Inorganic Elements in
the Chemistry of Life,’’ John Wiley, New York (1994), p. 373.
e) M. J. Abrams and B. A. Murrer, Science, 261, 725 (1993). f)
E. J. Corey, M. Mehrotra, and A. U. Khan, Science, 236, 68
(1987). g) M. Munakata, L. P. Wu, and G. L. Ning, Coord. Chem.
Rev., 198, 171 (2000).
Hpyrrld)2(H2O)(PPh3)2] H2O (1), [Ag(R-Hpyrrld)(PPh3)2]2
ꢁ
(2), their enantiomers 3 and 4, respectively, {[Ag(R,S-
Hpyrrld)(PPh3)]2}n (5), and [Ag(R,S-Hpyrrld)(PPh3)2] (6)
were determined. In the solid state, complex 1 having one
PPh3 ligand per silver(I) atom was a polymer formed by supra-
molecular arrangement of the dimeric unit [Ag(Hpyrrld)-
(PPh3)]2. In 1, the two protons of one coordinating water mole-
cule bridged between two silver(I) atoms with Ag–Ag interac-
ꢀ
tion (3.2854(7) A) significantly contributed to a formation of
2
a) R. V. Parish, Interdiscip. Sci. Rev., 17, 221 (1992). b)
the intermolecular hydrogen bonds with the carbonyl groups
of the Hpyrrldꢂ ligands in the neighboring unit. The dimeric
complex 2 having two PPh3 ligands per silver(I) atom was a
discrete centrosymmetric dimer of two AgP2O(carboxyl)-
O(carbonyl) units, while the dimeric complex 5 having one
PPh3 ligand per silver(I) atom was a meso-form of R- and S-
ligands, the dimeric units of which were further supramole-
R. J. Sue and P. J. Sadler, Met.-Based Drugs, 1, 107 (1994). c) D.
de Vos, P. Clements, S. M. Pyke, D. R. Smyth, and E. R. T.
Tiekink, Met.-Based Drugs, 6, 31 (1999). d) M. J. McKeage, P.
Papathanasiou, G. Salem, A. Sjaarda, G. F. Swiegers, P. Waring,
and S. B. Wild, Met.-Based Drugs, 5, 217 (1998).
3
a) F. Novelli, M. Recine, F. Sparatore, and C. Juliano, Il
Farmaco, 54, 232 (1999). b) S. P. Fricker, Gold Bull., 29, 53
(1996). c) A. M. Elsome, J. M. T. Hamilton-Miller, W. Brumfitt,
and W. C. Noble, J. Antimicrob. Chemother., 37, 911 (1996). d)
S. J. Berners-Price, R. K. Johnson, A. J. Giovenella, L. F.
Faucette, C. K. Mirabelli, and P. J. Sadler, J. Inorg. Biochem.,
33, 285 (1988). e) K. Nomiya, R. Noguchi, and M. Oda, Inorg.
Chim. Acta, 298, 24 (2000). f) K. Nomiya, R. Noguchi, T. Shigeta,
Y. Kondoh, K. Tsuda, K. Ohsawa, N. C. Kasuga, and M. Oda,
Bull. Chem. Soc. Jpn., 73, 1143 (2000). g) K. Nomiya, R.
Noguchi, K. Ohsawa, K. Tsuda, and M. Oda, J. Inorg. Biochem.,
78, 363 (2000).
cularly arranged with van der Waals contact (Ag1 O3ii
ꢁꢁꢁ
ꢀ
2.641 A) in the solid state. Complex 6 was a racemic com-
pound of R- and S-complexes, each of which was a 4-co-
ordinate monomer composed of a chelation with two carboxyl
oxygen atoms and two PPh3 ligands.
The Ag–O bonding modes in these silver(I) complexes were
different and were dependent upon both chirality of the
Hpyrrldꢂ ligand and the number of PPh3 ligands. Complexes
1–6 prepared here and the dimeric silver(I) precursors were
classified to four types (I–IV) based on the Ag–O bonding
modes formed among the silver(I) center, and the carboxyl
and/or carbonyl oxygen atoms in the Hpyrrldꢂ ligand. Forma-
tion of dimeric meso-form complex 5 from 1 and 3, and race-
mization from 2 and 4 producing 6 were also found. Solution
molecular weight measurements, solution and solid-state
31P NMR revealed that solution structures of 1–6 and their
behaviors in solution were quite different from those in the
solid state. Explicit correlation of the antimicrobial activities
with the number of soft PPh3 ligands per silver(I) atom was
found.
4
a) H. Veen and A. A. M. Kwakkenbos, Sci. Hortic.
(Amsterdam), 18, 277 (1982, 1983). b) H. Veen, Sci. Hortic.
(Amsterdam), 20, 211 (1983). c) K. M. Davies, G. E. Hobson,
and D. Grierson, Plant Cell Environ., 11, 729 (1988).
5
a) R. B. Thurman and C. P. Gerba, CRC Crit. Rev. Environ.
Control, 18, 295 (1989). b) R. Lopez-Garzon, M. A. Romero-
Molina, A. Navarrete-Guijosa, J. M. Lopez-Gonzalez, G.
Alvarez-Cienfuegos, and M. M. Herrador-Pino, J. Inorg. Bio-
chem., 38, 139 (1990). c) Q. L. Feng, J. Wu, G. Q. Chen, F. Z.
Cui, T. N. Kim, and J. O. Kim, J. Biomed. Mater. Res., 52, 662
(2000). d) A. D. Russell and W. B. Hugo, Prog. Med. Chem.,
31, 351 (1994). e) J. L. Clement and P. S. Jarrett, Met.-Based
Drugs, 1, 467 (1994). f) R. M. E. Richards, R. B. Taylor, and
D. K. L. Xing, J. Pharm. Sci., 80, 861 (1991).
This work was supported by a Grant-in-Aid for Scientific
Research and also by a High-tech Research Center Project,
both from the Ministry of Education, Culture, Sports, Science
and Technology, Japan.
6
a) K. Nomiya, S. Takahashi, R. Noguchi, S. Nemoto,
T. Takayama, and M. Oda, Inorg. Chem., 39, 3301 (2000). b)

1962 Bull. Chem. Soc. Jpn., 78, No. 11 (2005)
Structures of Phosphinesilver(I) Carboxylates
K. Nomiya, S. Takahashi, and R. Noguchi, J. Chem. Soc., Dalton
Trans., 2000, 4369. c) K. Nomiya, S. Takahashi, and R. Noguchi,
J. Chem. Soc., Dalton Trans., 2000, 1343. d) K. Nomiya and H.
Yokoyama, J. Chem. Soc., Dalton Trans., 2002, 2483. e) N. C.
Kasuga, A. Sugie, and K. Nomiya, Dalton Trans., 2004, 3732.
f) R. Noguchi, A. Hara, A. Sugie, S. Tanabe, and K. Nomiya,
Chem. Lett., 34, 578 (2005). g) R. Noguchi, A. Hara, A. Sugie,
and K. Nomiya, under submission.
7
G. M. Sheldrick, ‘‘SHELXL, version 5.1,’’ Bruker Analyt-
ical X-ray System, Inc., Madison, WI (1997).
R. Alessio, D. B. Dell‘Amico, F. Calderazzo, U. Englert,
A. Guarini, L. Labella, and P. Strasser, Helv. Chim. Acta, 81,
8
219 (1998).
9
Skelton, and A. H. White, J. Chem. Soc., Dalton Trans., 1999,
901.
G. A. Bowmaker, E. N. de Silva, P. C. Healy, B. W.