Monovalent K, Cs, Tl, and Ag nitrosodicyanomethanides: Completely different 3D networks with useful properties of luminescent materials and nonelectric sensors for gases?

Article abstract of DOI:10.1021/ic801364w

Four K, Cs, Ag(I), and Tl(I) compounds with a nitrosodicyanomethanide ONC(CN)₂ ^- anion have been obtained and characterized using IR spectroscopy; UV-visible spectroscopy; room temperature, solid-state photoluminescence; and solution

Full text of DOI:10.1021/ic801364w

Inorg. Chem. 2009, 48, 2371-2382
Monovalent K, Cs, Tl, and Ag Nitrosodicyanomethanides: Completely
Different 3D Networks with Useful Properties of Luminescent Materials
and Nonelectric Sensors for Gases†
Garrett Glover,‡ Nikolay Gerasimchuk,*,‡ Richard Biagioni,‡ and Konstantin V. Domasevitch§
Department of Chemistry, Temple Hall 456, Missouri State UniVersity, Springfield, Missouri 65897,
and Inorganic Chemistry DiVision, Chemistry Department of the National UniVersity of Ukraine,
Volodimirs’ka 64 St. KieV, 01033 Ukraine
Received August 22, 2008
Four K, Cs, Ag(I), and Tl(I) compounds with a nitrosodicyanomethanide ONC(CN)2- anion have been obtained
and characterized using IR spectroscopy; UV-visible spectroscopy; room temperature, solid-state photoluminescence;
and solutions electrical conductivity measurements. Cesium and thallium(I) complexes were obtained for the first
time, and crystal structures were determined for Cs{ONC(CN)2}, Ag{ONC(CN)2}, and Tl{ONC(CN)2}. These structures
indicate the formation of completely different 3D polymeric networks in which the anion acts as a bridging ligand
of different capacity. The cyanoxime ligand in all complexes studied is in the nitroso form and adopts a planar
configuration. The structure of the cesium salt is ionic. The structure of Ag{ONC(CN)2} represents a 3D coordination
polymer where the anion acts as a tetradentate ligand with all four bonds between Ag(I) and donor atoms (three
N and one O) significantly shorter than the sum of the ionic radii for these elements. The silver(I) atom in this
compound has a distorted tetrahedral surrounding. Additionally, Ag{ONC(CN)2} is remarkably UV- and visible-light-
insensitive. However, after exposure of the solid complex to gases such as H2, CO, NO, C2H2, and C2H4, the
surface of the compound becomes visible-light-sensitive and changes color with significant darkening, which indicates
reduction of the metal. This is reflected in a dramatic decrease of intensity of the photoluminescence of Ag{ONC(CN)2}
in the presence of these gases, which might be utilized for nonelectric sensor applications. The Tl{ONC(CN)2}
complex represents a transitional species between ionic (Cs) and covalent (Ag) compounds. The thallium(I) center
has four shorter bonds than the sum of the ionic radii bonds (three with N and one with O atoms) and three longer
electrostatic (ionic) contacts with the anion. The 6s2 lone pair is stereoactive, and the coordination polyhedron is
best described as a distorted square pyramid. Room temperature diffusion reflectance spectra of solid K{ONC(CN)2},
Ag{ONC(CN)2}, and Tl{ONC(CN)2} demonstrated a bathochromic shift of the band’s λmax depending on the atomic
number of the metal center, indicating a significant role of metal centers in electronic transitions in these compounds.
This phenomenon was observed for the first time. The latter complex at 293 K exhibited structured metal-based
red photoluminescence in the range of 690-800 nm that depends on the excitation wavelengths.
Introduction
ligands to act as multidentate bridges in numerous 3D metal
complexes. These compounds often demonstrate unusual
crystal structures with fascinating lattice architectures that
are useful in crystal engineering.3 Moreover, many of these
compounds have exhibited interesting magnetic properties,
such as the conjugated pseudohalogenide4 DCA and TCM
anions that affirm coupling between metal centers.5 The
nitrosodicyanomethanide, ONC(CN)2- (NDM), and nitrodi-
The coordination chemistry of small cyano-group-contain-
ing anions such as dicyanamide,1 N(CN)2 (DCA), and
-
tricyanomethanide,2 C(CN)3- (TCM), has received consider-
able attention in recent years due to the ability of these
†
Dedicated to Dr. Evgenii Pisarev, Kiev, on the occasion of his 50th
birthday.
* To whom correspondence should be addressed. E-mail: NNGerasimchuk@
missouristate.edu. Phone: (417) 836-5165.
-
cyanomethanide, O2NC(CN)2 (NTDM), analogues of the
‡
Missouri State University.
National University of Ukraine.
-
§
C(CN)3 anion were also examined as ligands in several
10.1021/ic801364w CCC: $40.75  2009 American Chemical Society
Inorganic Chemistry, Vol. 48, No. 6, 2009 2371
Published on Web 02/06/2009

Glover et al.
investigations of their ability to form metal complexes.6,7
The NDM- and NTDM- anions contain a considerable mass
percentage of nitrogen atoms being in both positive (formally
+1 and +5) and negative (-3) oxidation states, which
initiates interest for these compounds as potential high-energy
materials.8 The presence of heavy main group atoms9 and
especially heavy metal ions usually enhances the properties
of these compounds. These metal ions can be oxidizers (Ag+,
Pb2,4+, Hg2+)10 or can exhibit several stable oxidation states
and be involved in catalytic redox reactions (Cu2+, Fe3+,
Table 1. Results of Solid-State IR Spectroscopic Studies of Several
Metallo-Nitrosodicyanomethanides, Mn+{ONC(CN)2}n
vibrationsa in the IR spectra, cm-1
b
c
ν4
d
e
compound
ν1
ν5 ν6
reference
K{ONC(CN)2}
15N-labeled
2231, 2221
2231, 2220
1326 1275 793 6, 7
1312 1265 781 this work
NH4{ONC(CN)2} 2230, 2222
Cs{ONC(CN)2} 2230*, 2216, 2205 1310 1278 786 this work
Ba{ONC(CN)2}2 2239, 2228 1345 1263 n/a
1325 1274 n/a
7
7
Ag{ONC(CN)2}
2245, 2230
2245, 2230
2214, 2199
2214, 2200
1334 1292 814 this work
1316 1281 804 this work
1304 1279 790 this work
1293 1267 779 this work
15N-labeled
Tl{ONC(CN)2}
15N-labeled
a According to ref 7. b Corresponds to the stretching vibration ν(Ct N)
of the cyano group. c Corresponds to the in-plane stretching vibrations
ν(C-N) and ν(N-O), as well as the bending vibration δ(C-N-O) of the
nitroso group, which is also assigned as asν(CNO). d Corresponds to the
in-plane stretching vibrations ν(CdN) and the bending vibration δ(C-N-O)
(1) (a) Wu, A.-Q.; Zheng, F.-K.; Cai, L.-Z.; Guo, G.-C.; Huang, J.-S.
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of the nitroso group, which is also assigned as ν(CNO). e Corresponds to
s
the bending in-plane NC-C-NO vibrations.
Co2+, V4+).11 Nevertheless, the structural and coordination
chemistry of NDM- and NTDM- is not well-explored, and
aspects of the ligands’ binding in different complexes remain
largely unknown. Similarly, no information is available on
other physical properties including the photoluminescence
of these complexes alone or in the presence of different
gaseous substances. In this paper, we report the preparation,
spectroscopic and structural characterization, and solid-state
emission properties of three heavy metal complexes of
M{ONC(CN)2} composition, where M is monovalent Cs,
Ag, or Tl. The effect of exposure of Ag{ONC(CN)2} to UV
and visible light and a variety of gases is also described.
Experimental Section
Reagents. Inorganic reagents such as TlCl, AgNO3, and K2CO3
were obtained from Aldrich, whereas CsCl was supplied by City
Group Chemicals. 15N-labeled NaNO2 (98% enrichment) was
purchased from Cambridge Laboratories. Melting points or decom-
position temperatures for synthesized compounds were determined
using a Mel-Temp apparatus (Thomas-Hoover). Elemental analyses
of the C, H, and N content using the combustion method were
performed by Atlantic Microlab (Norcross, GA).
Spectroscopic Studies. The IR spectra of all synthesized
nitrosodicyanomethanide compounds were obtained at room tem-
perature using a Nicolet FT-IR spectrophotometer equipped with
OMNIC software. IR spectra of K{ONC(CN)2}, NH4{ONC(CN)2},
and Cs{ONC(CN)2} samples were recorded using 13 mm, round
KBr pellets in the range of 4000-450 cm-1 at 1 cm-1 resolution
limit using 128 accumulations, whereas spectra of Tl(CCO) and
Ag(CCO) were obtained from high-quality mulls prepared in
mineral oil and placed between two 2 cm KBr disks. The IR spectra
of these compounds are summarized in Table 1.
(3) (a) Schlueter, J. A.; Manson, J. L.; Geiser, U. Inorg. Chem. 2005, 44,
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K. S. Chem.sEur. J. 2000, 6, 3186. (c) Schlueter, J. A.; Geiser, U.;
Manson, J. L. J. Phys. IV 2004, 114, 475. (d) Ghoshal, D.; Ghosh,
A. K.; Ribas, J.; Zangrando, E.; Mostafa, G.; Maji, T. K.; Chaudhuri,
N. R. Cryst. Growth Des. 2005, 5, 941. (e) Sun, H.-L.; Gao, S.; Ma,
B.-Q.; Batten, S. R. CrystEngComm. 2004, 6, 579. (f) Lin, H.-H.;
Mohanta, S.; Lee, C.-J.; Wei, H.-H. Inorg. Chem. 2003, 42, 1584. (g)
Kutasi, A.; Harris, A. R.; Batten, S. R.; Moubaraki, B.; Murray, K. S.
Cryst. Growth Des. 2004, 4, 605. (h) Batten, S. R.; Murray, K. S.
Coord. Chem. ReV. 2003, 246, 103.
(4) Golub, A. M.; Ko¨hler, H.; Skopenko, V. V. In Chemistry of
Pseudohalides ; Clark, R. J. H., Ed.; Topics in Inorganic and General
Chemistry, Monograph 21; Elsevier: Amsterdam, 1986.
(5) For DCM: (a) Kurmoo, M. Mol. Cryst. Liq. Cryst. Sci. Technol., Sect.
A 2000, 342, 167. (b) Zhang, L.-Y.; Shi, L.-X.; Chen, Z.-N. Inorg.
Chem. 2003, 42, 633. (c) Kuang, S.-M.; Fanwick, P. E.; Walton, R. A.
Inorg. Chem. 2002, 41, 147. (d) Sun, H.-L.; Gao, S.; Ma, B.-Q.; Su,
G. Inorg. Chem. 2003, 42, 5399. For TCM: (e) Schlueter, J. A.;
Manson, J. L.; Geiser, U. Inorg. Chem. 2005, 44, 3194. (f) Manson,
J. L.; Ressouche, E.; Miller, J. S. Inorg. Chem. 2000, 39, 1135. (g)
Miyasaka, H.; Clerac, R.; Campos-Fernandez, C. S.; Dunbar, K. R.
Inorg. Chem. 2001, 40, 1663.
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Ko¨hler, H.; Lux, G. Inorg. Nucl. Chem. Lett. 1977, 31A, 151.
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1999, 38, 2709.
(8) (a) Orlova, E. Yu. Chemistry and Technology of ExplosiVe Substances,
3rd ed.; Khimiya, Leningradskoe Otdelenie: Leningrad, USSR, 1981;
(Russ.). (b) Urbanski, T. Chemistry and Technology of ExplosiVes;
Pergamon Press: Oxford, U.K., 1984. (c) Nielsen, A. T. In Chemistry
of Energetic Materials; Olah, G. A. , Squire, D. R., Eds.; Academia
Press, Inc.: San Diego, CA , 1991. (d) Klapo¨tke, T. M., Ed. High
Energy Density Materials; Structure and Bonding, Vol. 125; Springer-
Verlag: Germany, 2007. (e) Meyer, R. ExplosiVes, 3rd ed.; Wiley-
VCH: Weinheim, Germany, 1987.
Solid-state diffusion reflectance spectra of fine powders of
K{ONC(CN)2}, Tl{ONC(CN)2}, and Ag{ONC(CN)2} were re-
corded at room temperature using a Cary Bio 100 spectrophotometer
equipped with a white reflectance sphere unit (Spectralon coating)
using pure MgO as the reflectance standard.
Solid-state, room temperature photoluminescence spectra from
fine powders of K{ONC(CN)2}, Cs{ONC(CN)2}, Tl{ONC(CN)2},
and Ag{ONC(CN)2} were recorded on a Shimadzu RF-5301 PC
spectrofluorimeter using a wooden insert for holding solid samples
(Supporting Information, S1), in the range of 300-900 nm. The
data sampling interval was set to 1 nm, and the slit width for both
2372 Inorganic Chemistry, Vol. 48, No. 6, 2009

MonoWalent K, Cs, Tl, and Ag Nitrosodicyanomethanides
Table 2. Crystal and Refinement Data for Studied Compounds
parameter
Ag{ONC(CN)2}
Cs{ONC(CN)2}
Tl{ONC(CN)2}
formula
mol wt, amu
color, shape
C3N3OAg
201.9
yellow block
0.28 × 0.25 × 0.25
294
C3N3OCs
226.9
yellow prism
0.15 × 0.18 × 0.55
296
C3N3OTl
298.4
orange block
0.40 × 0.33 × 0.30
296
crystal size, mm
temperature, K
density, g/cm3
2.823
2.606
3.820
crystal system
space group
orthorhombic
Pbca
monoclinic
P2(1)/c
monoclinic
C2/c
unit cell, Å, °
a
10.3063(13)
7.9860(10)
11.5458(15)
90
90
90
950.3
8
4.11
11192
7.8163(9)
13.1372(15)
5.6498(6)
90
94.385(14)
90
578.4(11)
4
6.29
9059
1762
408
2.61-30.50
-11 < h < 11
-18 < k < 18
-8 < l < 8
direct methods
1762/0/74
1.107
15.5346(12)
8.2402(5)
10.5347(9)
90
129.692(6)
90
1037.68(14)
8
31.01
4380
1289
1024
4.56-28.70
-20 < h < 20
-10 < k < 11
-13 < l < 13
direct methods
1289/0/73
1.139
b
c
R
ꢀ
γ
volume, Å3
Z
abs coeff, µ mm-1
total reflns
independent reflns
F[000]
1091
752
o
θ range,
3.53-27.48
-13 < h < 13
-10 < k <10
-14 < l < 14
direct methods
1091/0/74
1.089
indexes range
solution
data/restrain/parameter
GOF on F2
refinement
R1 [I > 2σ(I)]
wR2
full matrix F2
R1 ) 0.0237
wR2 ) 0.0591
R1 ) 0.0245
wR2 ) 0.0591
1.11 and -1.00
full matrix F2
R1) 0.0336
wR2 ) 0.0817
R1 ) 0.0357
wR2 ) 0.0830
1.35 and -1.65
full matrix F2
R1 ) 0.0276
wR2 ) 0.0829
R1 ) 0.0290
wR2 ) 0.0840
1.59 and -1.35
R indexes (all data)
wR2
largest difference peak/hole (e.Å-3
)
Table 3. Bond Lengths and Selected Angles for the
Nitrosodicyanomethanide Anion in M{ONC(CN)2} Complexesa
(Supporting Information, S3). These gases were collected in a 1 L,
round-bottom flask at ∼800 Torr using standard operations with a
Schlenk line and then released into a cell prevacuumed to 0.1 Torr
(Supporting Information, S2) that contained solid, powdery samples
of Tl{ONC(CN)2} or Ag{ONC(CN)2} complexes covering a 2 cm2
area. The cell was transferred into the cuvette compartment of a
Shimadzu RF-5301 PC spectrofluorimeter for measurements.
The light sensitivity and stability of synthesized Ag{ONC(CN)2}
were studied at 296 K using a low-pressure Hg lamp with >85%
output at λmax ) 254 nm with the intensity of light measured by
the UVX radiometer. A sample of the complex, prior to investiga-
tion, was thoroughly dried under high vacuum (<10-4 Torr) and
ground in an agate mortar. For these studies, samples of the complex
were gently spread on white cardboard and covered with a black,
square mask, leaving an area of 1 cm2 for irradiation. The radiation
source was positioned at a 2 cm distance from the sample
(Supporting Information, S4). Digital pictures of irradiated samples
were taken every 30 min using a stationary digital camera (Kodak
DX7630, 6.1 Mpxl), and images were processed without the use
of any filtering or enhancement using Digimax Viewer 2.0 software
(Samsung).
compound
Ag
bond length, Å
valence angle, °
C1-C2 ) 1.424(4)
C1-C3 ) 1.427(4)
C2-N2 ) 1.142(4)
C3-N3 ) 1.136(4)
N1-C1 ) 1.331(4)
O1-N1) 1.278(3)
C1-C2 ) 1.401(5)
C1-C3 ) 1.407(5)
C2-N2 ) 1.139(5)
C3-N3 ) 1.139(5)
N1-C1 ) 1.351(5)
O1-N1 ) 1.250(5)
C1-C2 ) 1.398(12)
C1-C3 ) 1.434(12)
C2-N2 ) 1.146(12)
C3-N3 ) 1.135(13)
N1-C1 ) 1.362(11)
O1-N1 ) 1.236(10)
N1-C1-C3 ) 123.6(3)
N1-C1-C2 ) 116.1(3)
N3-C3-C1 ) 178.7(4)
N2-C2-C1 ) 177.8(3)
O1-N1-C1 ) 116.4(2)
C2-C1-C3 ) 120.3(3)
N1-C1-C2 ) 116.9(3)
N3-C3-C1 ) 177.2(4)
N2-C2-C1 ) 178.4(4)
O1-N1-C1 ) 117.1(4)
N1-C1-C3 ) 121.6(3)
C2-C1-C3 ) 121.5(3)
N1-C1-C2 ) 117.4(7)
N1-C1-C3 ) 122.6(8)
N2-C2-C1 ) 178.9(10)
N3-C3-C1 ) 177.5(10)
O1-N1-C1 ) 114.9(7)
C2-C1-C3 ) 120.0(7)
Cs
Tl
a Geometry around metal centers is presented in S6, S7, and S8 in the
Supporting Information.
Solution Electrical Conductivity. The electrical conductivity
of 1 mM solutions of Cs{ONC(CN)2}, Tl{ONC(CN)2}, and
Ag{ONC(CN)2} in anhydrous DMSO was measured at 296 K using
excitation and emission was 5 nm. All spectroscopic data were
processed and graphed using Origin 6.0 software.
Photophysical Measurements. To investigate the photolumi-
nescent response of solid samples of Tl and Ag complexes in the
presence of different gases, we have designed and built a special
cell for these kind of measurements at ambient temperature
(Supporting Information, S2). Compressed gases such as H2, CO,
acetylene C2H2, and ethylene C2H4 were obtained compressed in
steel cylinders from commercial sources with purity >98%. At the
same time, small quantities of pure and dry NH3, SO2, and NO
were obtained by chemical means33,34 from appropriate precursors
(9) (a) Klapo¨tke, T. M.; Krumm, B.; Scherr, M.; Haiges, R.; Christe, K. O.
Angew. Chem., Int. Ed. 2007, 46, 8686–8690. (b) Klapo¨tke, T. M.;
Krumm, B.; Schwab, I. Phosphorus, Sulfur Silicon Relat. Elem. 2005,
180, 957. (c) Klapo¨tke, T. M.; Krumm, R.; Mayer, P.; Schwab, I.
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B. J. Am. Chem. Soc. 2004, 126, 710. (e) Karaghiosoff, K.; Klapo¨tke,
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Inorganic Chemistry, Vol. 48, No. 6, 2009 2373

Glover et al.
detector. The radiation source was a Mo tube (KR radiation, λ )
0.71073 Å) with a highly oriented graphite monochromator.
Intensities were integrated from four series of 366 exposures, each
covering 0.5° in ω within 50 s of acquisition time, with the total
data set being a sphere.12 The space group determination was done
with the aid of XPREP software.14 Absorption corrections were
applied on the basis of crystal face indexing obtained using actual
images recorded by video camera. The following data processing
was performed using the SADABS program that was included in
the Bruker AXS software package.13The structures were solved by
direct methods and refined by least-squares on weighted F2 values
for all reflections using the SHELXTL-XL program.14 All atoms
received assigned anisotropic displacement parameters and were
refined without positional constraints. Crystal data for the com-
pounds studied are presented in Table 2, whereas bond lengths and
valence angles are summarized in Table 3. Figures for the crystal
structures of these complexes were drawn using Mercury 4.1.2 and
ORTEP 3 software15 at 50% thermal ellipsoids probability level.
The PLATON checks of crystallographic data and actual CIF files
for reported structures can be found in the Supporting Information.
Synthesis. As reported in this work, K, Cs, and Tl nitrosodi-
cyanomethanides were obtained using a heterogeneous metathesis
reaction from Ag{ONC(CN)2}, which is only sparingly soluble in
water at room temperature. In this reaction, silver chloride is the
least soluble substance:
Ag{ONC(CN)2}(s) + MCl(aq) f AgCl(s) + M{ONC(CN)2}(aq), where
M ) K, Cs, Tl
The typical preparation of monovalent nitrosodicyanomethanides
is given for Tl complex only.
Tl{ONC(CN)2}. Ag(CCO) (0.135 g, 0.67 mM) as a fine powder
was suspended in 10 mL of water by intensive stirring, at which
point 0.161 g (0.67 mM) of white solid TlCl was added slowly to
the suspension. The aqueous solution immediately turned a deep
yellow color, and flaky white AgCl precipitate appeared. After
stirring in the dark for another 20 min, the solution was filtered
and washed with 2 mL of water. The clear yellow solution of
Tl{ONC(CN)2} was left at 4 °C for crystallization and, after 2
weeks, resulted in crystalline, dark-orange prisms suitable for X-ray
analysis (Supporting Information, S5). Yield: 0.18 g (90%). Mp )
142 °C. Mp ) 205-209 ·C Anal. Calcd for C3N3OTl (Found): C,
12.07 (12.11); N, 14.08 (14.02).
Other nitrosodicyanomethanides follow.
K{ONC(CN)2}. Bright yellow crystals were obtained after the
(10) (a) Bagal, L. I. Chemistry and Technology of the Initiating ExplosiVe
Substances; Nauka: Moscow, 1975 (Russ.). (b) Beck, W.; Klapo¨tke,
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Z. Anorg. Allg. Chem. 2001, 627, 1669. (f) Klapo¨tke, T. M.; Krumm,
B.; Niemitz, M.; Polborn, K.; Riena¨cker, C. M. J. Fluorine Chem.
2000, 104, 129.
(11) (a) Geisberger, G.; Klapo¨tke, T. M.; Stierstorfer, J. Eur. J. Inorg. Chem.
2007, 4743. (b) Beck, W.; Klapo¨tke, T. M. Z. Naturforsch. 2001, 56b,
1376. (c) Seok, W. K.; Lee, H. N.; Kim, M. Y.; Klapo¨tke, T. M.;
Dong, Y.; Yun, H. J. Organomet. Chem. 2002, 654, 170. (d) Klapo¨tke,
T. M.; Polborn, K.; Schu¨tt, T. Z. Anorg. Allg. Chem. 2000, 626, 1444.
(12) SAINT: Data Integration Program; Bruker AXS, 1998.
(13) (a) Blessing, R. H. Acta Crystallogr. 1995, A51, 33. (b) Sheldrick,
G. M. SADABS: Area Detector Absorption Correction, version 2.03;
University of Go¨ttingen, Go¨ttingen, Germany, 1999.
Figure 1. Fragments of the 3D polymeric structure of Ag{ONC(CN)2}.
Two orthogonal views of the unit cell: A, along b; B, along c. Coloring
scheme: Ag, magenta; C, gray; N, blue; O, red.
a YSI conductance-resistance meter model 34. Solutions of
ammonium bromide, tetrabutylammonium bromide, tetraphenylphos-
phonium bromide (as 1:1 electrolytes), and hydrazinium dichloride
(as 1:2 electrolytes) were used for the electrode calibration.
X-ray Crystallography. Single crystals of Tl{ONC(CN)2} and
Cs{ONC(CN)2} were obtained from aqueous solutions upon slow
evaporation at 4 °C, (Supporting Information, S5). Crystals of
Ag{ONC(CN)2} were grown from a hot, saturated solution of the
complex in water upon slow cooling in thermostat. Crystal structures
were determined at room temperature from a suitable specimen
mounted on a plastic fiber using thick Paraton oil. Diffraction
measurements were made using a Bruker APEX2 instrument
working in ω-scan mode and equipped with a SMART CCD area
(14) SHELXTL-XL: Crystal Structure Refinement, version 6.10; Bruker
AXS, 2001.
(15) (a) Farrugia, L. J. Appl. Crystallogr. 1997, 30, 565. (b) Burnett, M. N.;
Johnson, C. K. ORTEP III: Report ORNL-6895; Oak Ridge National
Laboratory, Oak Ridge, TN, 1996.
2374 Inorganic Chemistry, Vol. 48, No. 6, 2009

MonoWalent K, Cs, Tl, and Ag Nitrosodicyanomethanides
Figure 2. Numbering scheme and molecular structure of Ag{ONC(CN)2}: A, one anion and closest metal ions; B, surrounding of Ag(I) center.
Figure 3. Asymmetric unit in the structure of Cs{ONC(CN)2} with atomic
numbering scheme and closest metal cation.
reaction of 1.00 g (5 mM) of Ag{ONC(CN)2} with 0.59 g (5.0
mM) of KBr. Yield of K{ONC(CN)2} ) 0.65 g (98%). Mp )
205-209 °C. Anal. Calcd for C3N3OK (Found): C, 27.06 (27.17);
N, 31.56 (31.62).
Cs{ONC(CN)2}. Yellow-orange crystals were obtained after the
reaction of 0.662 g (3.28 mM) of Ag{ONC(CN)2}with 0.552 g (3.28
mM) of CsCl. Yield of Cs{ONC(CN)2} ) 0.63 g (85%). Mp )
159 °C. Anal. Calcd for C3N3OCs (Found): C, 15.88 (15.93); N,
18.51 (18.74).
Figure 4. Fragments of the 3D ionic structure of Cs{ONC(CN)2}. Two
Ag{ONC(CN)2}. Bright deep-yellow microcrystalline powder
was obtained (pure) after precipitation of the {ONC(CN)2}- anion
with AgNO3 from the reaction mixture.16 Ag{ONC(CN)2} decom-
poses in the range of 175-210 °C. Anal. Calcd for C3N3OAg
(Found): C, 17.84 (17.98); N, 20.81 (20.69).
The synthesis of 15N (50% dilution with 14N for observation of
bands splitting in the IR spectra) isotopomeric compounds was
carried out in a similar manner.
The obtained monovalent nitrosodicyanomethanides of K, Cs,
and Tl are water soluble compounds at room temperature, whereas
Ag{ONC(CN)2} is sparingly soluble in boiling water. All four
compounds are highly soluble in DMF, DMSO, and Py at 296 K,
but not soluble in light alcohols, acetone, and chlorohydrocarbons.
Both Tl{ONC(CN)2} and Ag{ONC(CN)2} exhibit remarkable
stability to visible light (Supporting Information, S5).
orthogonal projections of the unit cell: A, along the a axis; B, along the c
axis. Coloring scheme: Cs, orange; C, gray; N, blue; O, red.
Safety Note! Although we haVe not encountered any problems
during many years of laboratory work and handling, special care
should be taken during procedures using thallium compounds
because of their toxicity.38,39 Gloves are required at all times since
solutions are easily absorbed through the skin.
(16) Longo, G. Gazz. Chim. Ital. 1931, 61, 575.
(17) CRC Handbook of Chemistry and Physics, 67th ed.; Weast, R. C.,
Astle, M. J., Beyer, W. H., Eds.; CRC Press: Boca Raton, FL, 1986.
(18) Chow, Y. M.; Britton, D. Acta Crystallogr. 1974, B30, 1117.
Inorganic Chemistry, Vol. 48, No. 6, 2009 2375

Glover et al.
Figure 5. Numbering scheme in Tl{ONC(CN)2}: A, one anion and closest
Tl(I) cations; B, building block in the structure that consists of an orthogonal
planar Tl(1)2N(2)2 rhomb and a planar hexagonal Tl(1)2N(1)2O(1)2 metal-
locycle.
Results and Discussion
Figure 6. Fragments of the 3D network in the structure of Tl{ONC(CN)2}:
A, B, and C are three views of the unit cell along a, b, and c directions,
respectively. Coloring scheme: Tl, green; C, gray; N, blue; O, red.
Structures of Synthesized M+ Nitrosodicyanomethani-
des. All synthesized ONC(CN)2 -based compounds dis-
-
cussed in this paper represent coordination polymers of
totally different structures. This can be attributed to two
factors: (a) diverse ionic radii of heavy metal atoms17 (Ag+
for 1.26, Tl+ for 1.47, and Cs+ for 1.67 Å) lead to a
significant increase of the cation’s volume (3.79 for Ag+,
4.84 for Tl+, and 6.21 Å3 for Cs+), which affects crystal
packing and (b) distinct character of binding between the
anion and different cations, ranging from purely ionic for
Cs{ONC(CN)2}, partially covalent/ionic for Tl{ONC(CN)2},
to covalent for Ag{ONC(CN)2}. It is our belief that the
observed structural differences in M{ONC(CN)2} compounds
are primarily affected by the second factor rather than the
size of heavy metal cations.
Ag{ONC(CN)2}. The structure of this complex was
previously reported18 in the 1970s but suffered from poor
data quality and errors in the ligand bond lengths. Using
modern equipment and superior crystal specimens, we were
able to determine the geometry of the ligand and metal center
much more accurately, although the general structural motif
remained the same. Thus, silver(I) nitrosodicyanomethanide
represents a 3D interwoven coordination polymer organiza-
tion, which is shown in Figure 1. All donor atoms of the
functional groups of ONC(CN)2- are involved in coordina-
tion to Ag(I), therefore, bringing the denticity of the ligand
to four (Figure 2). The anion is planar and adopts the nitroso
form: the N1-O1 bond length is shorter (1.278(3) Å) than
the C1-N1 bond length (1.331(4) Å) (Table 3). A complex
polymeric structure of this compound can be dissected into
planar sheets formed by four silver(I) centers and four
cyanoxime anions (Supporting Information, S6). These sheets
are connected via N3 atoms of identical neighboring sheets
(angled at ∼60°) into an interwoven 3D framework (Figure
1A). The shortest Ag(I) · · · Ag(I) distance is 3.677 Å. The
coordination polyhedron of the Ag(I) center can be described
as a distorted tetrahedron (Supporting Information, S7). All
four Ag-L bond lengths are significantly shorter than the
sum of Ag-O (2.58 Å)17 and Ag-N (2.97 Å)17 ionic radii,
which indicates the covalent character of those bonds. This
explains the very poor room temperature solubility of
Ag{ONC(CN)2} in aqueous solutions and short chain alco-
hols, as well as the remarkable visible-light insensitivity of
the complex as observed over many years. The latter property
is highly atypical of the silver(I) compounds and may have
a variety of practical applications.
2376 Inorganic Chemistry, Vol. 48, No. 6, 2009

MonoWalent K, Cs, Tl, and Ag Nitrosodicyanomethanides
Tl{ONC(CN)2}. Monovalent thallium forms a completely
different structure from Ag{ONC(CN)2} and Cs{ONC-
(CN)2}, although the anion acts similarly as a bridging ligand
(Figure 5A and Figure S9 in the Supporting Information).
First of all, there are clearly two different sets of Tl-N,O
distances: four short and two long ones (Figures 6 and 7).
Thus, three Tl1-nitrogen (N2,N1) bonds range from 2.93
to 3.05 Å and are shorter than the sum of the ionic radii of
Tl-N ) 3.18 Å,17 indicating predominantly covalent char-
acter of these bonds. At the same time, only one thallium-
oxygen bond Tl1-O1 ) 2.749 Å is shorter than the sum of
the ionic radii (2.79 Å) of these elements, whereas the second
one is considerably longer (2.949 Å) and is responsible for
bridging between building blocks during crystal packing
(Figure 5B). This situation with two sets of shorter (covalent)
and longer (ionic) bonds is rather typical19 for large metal
cationss“soft” acids such as Hg+, Sn2+, Pb2+, and Tl+. The
ONC(CN)2- anion in this complex is planar and in the nitroso
form, which is evident from an almost purely double NdO
bond equal to 1.236 Å (Table 3).
The geometry of the coordination polyhedron around Tl(I)
in Tl{ONC(CN)2} can be described as a distorted tetragonal
pyramid and is shown in S9 in the Supporting Information.
The organization of crystal packing in Tl{ONC(CN)2} is
complex and is shown in Figure 6 and Figure S10 in the
Supporting Information. There are infinite zigzag chains of
joined alternating and distorted nonplanar Tl2O2 rhombs and
undistorted planar Tl2N2 rhombs that form a 3D framework
with the help of a bridging anion. Because there are two
different rhombs (Supporting Information, S10) in the
structure, there are two Tl · · ·Tl distances of 4.233 and 4.258
Å, respectively, but none of them can be considered as
metal-metal bonds. The angle between Tl · · · Tl · · · Tl atoms
is 103.8° in a zigzag chain (Supporting Information, S10).
IR Spectra. Vibrational frequencies in the IR spectra of
K, Cs, Tl, and Ag nitrosodicyanomethanides are presented
in Table 1, and the established binding modes of the anion
are summarized in Table 4. Despite its simplicity, several
different types of coordination of the ONC(CN)2- ligand to
a variety of metal centers were documented using X-ray
analysis and vibrational spectroscopy with 15N labels. The
introduction of the label at a 50% level allowed for
unambiguous assignment of stretching and bending vibrations
with participation of the >C-N-O fragment in the IR
spectra of each compound (Figure 7). This level of isotopic
enrichment allows observation of clear splitting of the bands
of isotopomers in the spectra, as opposed to just a small
∼10-15 cm-1 shift in pure 15N-enriched compounds. This
shift often is not well-seen or obscured, especially if the
spectra were recorded at different instrument parameters or
from different samples of variable quality. Monodentate (via
N or O atoms) coordination or bridging upon binding to a
variety of metal ions greatly affected the position of the key
sν(CNO) and asν(CNO) vibrations6,7,20 (Table 4). In general,
these changes correlate with the nature of the metal center
in the complex (its ability to participate in π-back-bonding
in the case of Fe, Ru, Ir, and Re) and reflect the distribution
of electron density in the ligand (nitroso or oxime forms,
Figure 7. Overlaid fragments of the IR spectra of K{ONC(CN)2} in KBr
pellets (A) and Ag{ONC(CN)2} and Tl{ONC(CN)2} in Nujol mulls (B and
C, respectively). Asterisks indicate 15N isotopomer bands.
Cs{ONC(CN)2}. The anion in this compound adopts
planar geometry and is in the nitroso form (Table 3), judging
from the N1-O1 bonds being significantly shorter than the
-
N1-C1 bonds (Figure 3). The ONC(CN)2 anion acts as a
bridging group between several Cs centers. The Cs{ONC-
(CN)2} is an ionic compound in which all metal-ligand
distances are longer than the sum of Cs-N (3.03) and Cs-O
(2.99 Å) ionic radii. For this group of compounds, especially
with large metal cations, preferential binding of donor atoms
to the metal center is not observed but, rather, uniform spatial
distribution. There are 10 electrostatic contacts ranging from
3.053 to 3.653 Å for the Cs1 ion, which include eight
nitrogen atoms and two oxygen atoms (Supporting Informa-
tion, S8), with Cs1-O1 ) 3.053 Å being the shortest of the
ASUs. Therefore, the coordination environment of Cs1 in
this compound is best described as an irregular polyhedron.
The crystal packing of Cs{ONC(CN)2} is rather complex
and is shown in Figure 4.
Inorganic Chemistry, Vol. 48, No. 6, 2009 2377

Glover et al.
-
Table 4. Summarized Binding Modes of the Nitrosodicyanomethanide Ion, ONC(CN)2 (L) in Different Complexes
monodentate or bridging function, etc.). Nevertheless, there
are no simple or direct relationships between values of bond
lengths, angles, and vibrational frequencies for the com-
pounds studied by IR spectroscopy. As an example, the
known geometric parameters of ONC(CN)2 being mono-
dentate in transition-metal complexes versus the IR data are
summarized in S11 in the Supporting Information.
presented in Table 5. The difference between three standard
salts, NH4Br, N(C4H9)4Br, and P(C6H5)4Br, is due to different
mobility of the cations in viscous, room temperature DMSO.
Clearly, ionic K+ and Cs+ salts of nitrosodicyanomethanide
exhibit a 1:1 electrolyte ratio in solutions, closely followed
by Tl{ONC(CN)2}, whereas the Ag{ONC(CN)2} complex
-
(19) Wells, A. F. Structural Inorganic Chemistry, 3rd ed.; Clarendon Press:
Oxford, U.K., 1962.
(20) Kolbe, A.; Ko¨hler, H. Z. Anorg. Allg. Chem. 1970, 373, 230.
Solution Electrical Conductivity. Values of measured
conductivities of millimolar solutions of compounds are
2378 Inorganic Chemistry, Vol. 48, No. 6, 2009

MonoWalent K, Cs, Tl, and Ag Nitrosodicyanomethanides
Table 5. Results of Measurements of Electrical Conductivity of 0.001
M Solutions of Compounds in Pure DMSO
conductivity, electrolyte
compound
µS
type
DMSO
1.2 ( 0.2
43 ( 2
24 ( 1
21 ( 1
76 ( 3
40 ( 2
36 ( 1
34 ( 1
28 ( 1
ammonium bromide, NH4Br
tetrabutylammonium bromide, N(C4H9)4Br
tetraphenylphosphonium bromide, P(C6H5)4Br
hydrazinium dichloride, N2H6Cl2
K{ONC(CN)2}
Cs{ONC(CN)2}
Tl{ONC(CN)2}
Ag{ONC(CN)2}
1:1
1:1
1:1
1:2
1:1
1:1
1:1
1:1
Figure 10. Results of photosensitivity studies of solid, powdery
Ag{ONC)CN)2} and simple inorganic AgCl and AgNO3 salts toward UV
radiation (λmax ) 254 nm) (A) and high sensitization of Ag{ONC)CN)2}
toward visible light after exposure to acetylene C2H2 (B).
shows lesser dissociation. This observation is in line with
results of X-ray analysis indicating covalent bonding in the
Ag+ complex, intermediate bonding between ionic and
covalent for the Tl+ complex, and the K+ and Cs+ salts being
completely ionic.
UV-Visible Spectra. A planar conjugated yellow nitro-
sodicyanomethanide anion32 forms numerous coordination
-
compounds. The color of the ONC(CN)2 system is due to
a n f π* transition at ∼390-450 nm in the nitroso
chromophore. This transition is weak (ꢀ ) 20-100) and
exhibits strong solvent dependence (negative solvatochromic
effect).21 The UV-visible spectra of K{ONC(CN)2}, Cs-
{ONC(CN)2}, and Tl{ONC(CN)2} in water and Ag{ONC-
(CN)2} in hot water are practically identical, which suggest
Figure 8. Diffusion reflectance spectra of M{ONC(CN)2}. Inset shows
the dependence of λmax for the n f π* intraligand transition upon the atomic
number of the metal.
Figure 11. Changes in the photoluminescence of solid Ag{ONC(CN)2}
in the presence of acetylene (A) and H2 (B). Excitation wavelength is 300
nm, and asterisks indicate instrument artifacts (multiple harmonics of the
main line).
the loss of structural peculiarities in aqueous solutions that
are observed in the solid state. There are hydrated ON-
-
C(CN)2 anions and K+ and Cs+ cations in solutions.
However, solid-state reflectance spectra of synthesized and
studied M{ONC(CN)2} (M ) K, Cs, Ag, and Tl) compounds
are different and show four bands in the 320-900 nm range
(Figure 8), which belong to π f π*, n f π*, and n* f π*
transitions. A full line-shape analysis of solid-state, UV-
visible reflectance spectra allowed for the deconvolution of
four Gaussian-type bands that show very good agreement
with experiment (Supporting Information, S12-S14). There
Figure 9. Unnormalized solid-state, room temperature, metal-based red
photoluminescence spectra of fine powder of Tl{ONC(CN)2}.
Inorganic Chemistry, Vol. 48, No. 6, 2009 2379

Glover et al.
electronic transitions for a compound and the total number
of electrons on the metal ion.
Solid-State Photoluminescence. Because studied M{ONC-
(CN)2} compounds demonstrated interesting and completely
different 3D polymeric structures, we decided to examine
their solid-state emission spectra at room temperature since
there was a good possibility to observe metal-based photo-
luminescence in these dense metal complexes. The most
interesting cases turned out to be Ag{ONC(CN)2} and
Tl{ONC(CN)2} complexes that both showed ligand-based
transitions around 380 and 500 nm at room temperature.
However, the thallium(I) compound also exhibited a strong
metal-centered emission in the region above 650 nm (Figure
9). It appears that the shape and position of these photolu-
minescence signals depend on the excitation wavelength
(Figure 9) where a large Stokes shift was observed between
the emission and excitation maxima. This is known for
monovalent Tl, which demonstrates high intensity Raman
spectra in its inorganic halide complexes.23 An assignment
of a metal-to-ligand charge transfer (MLCT) state from Tl(I)
to π* of the ONC(CN)2- anion is very likely since thallium
is known to form a stable Tl(III) oxidation state. In such a
case, only two M f L electron transitions from the
participating 6s2 electron pair of Tl are possible due to the
absence of a Tl(II) oxidation state. Also, Tl(I) is known for
its long-lived excited state followed by emission of photons,
which is utilized in NaI crystals, doped by Tl(I), as
scincillation detectors of X-ray and γ radiation. Detailed line-
shape analysis of the Tl{ONC(CN)2} solid-state, room
temperature emission at four studied wavelengths is presented
in S16-S19 in the Supporting Information. There is only
one Gaussian-type line for the λexc ) 300 nm emission in
the photoluminescence (PL) spectrum of Tl{ONC(CN)2},
whereas two Gaussian-type lines were required to fit the
experimental emission profile in the PL spectra at 350, 400,
and 450 nm excitations. In all cases, these lines demonstrate
significantly different line widths, which suggest different
lifetimes for both excited states.
Figure 12. Changes in the photoluminescence of solid Ag{ONC(CN)2}
in the presence of NO (A) and CO (B). Excitation wavelength is 300 nm,
and asterisks indicate instrument artifacts (multiple harmonics of the main
line).
are two n f π* bands of significantly different widths in
the same spectroscopic envelope (Supporting Information,
S12-S14). Previously, we observed the same feature for
several other cyanoxime anions,22 but at that time, only in
DMF and DMSO solutions. The most interesting feature of
these spectra is that they exhibit weak broad bands for n*
f π* transitions at unusually high wavelengths. Moreover,
values of λmax for the intraligand n f π* and π f π*
transitions surprisingly demonstrate correlation with the
number of electrons on the metal ion in M{ONC(CN)2}
compounds (Figure 8 and Figure S15 in the Supporting
Information).
There is a pronounced bathochromic shift of the band
positions with the increase of the atomic weight of the metal
cation. This indicates definite interaction between the
electrons of metal centers and the electrons of bridging
anions. To the best of our knowledge, this is the first case
of an established correlation between the ligand-based
Photostablity Studies. We have mentioned a remarkable
visible-light insensitivity of several silver(I) cyanoximates
in the past,35 but, in this work, we examined the stability of
one particular compound, Ag{ONC(CN)2}, toward short
(23) (a) Spiro, T. G. Inorg. Chem. 1965, 4, 731. (b) Maroni, V. A.; Spiro,
T. G. Inorg. Chem. 1968, 7, 193. (c) Biedermann, G.; Spiro, T. G.
Chem. Scr. 1971, 1, 155.
(24) Skopenko, V. V.; Zub, Y. L.; Porai-Koshits, M. A.; Sadikov, G. G.
Ukr. Khim. Zh. 1979, 45, 811.
(25) Fritsch, E.; Polborn, K.; Su¨nkel, K.; Beck, W.; Ko¨hler, H.; Jager, L.
Z. Anorg. Allg. Chem. 1992, 617, 110.
(26) Ko¨hler, H.; Seifert, B. Z. Anorg. Allg. Chem. 1968, 360, 137.
(27) Ko¨hler, H.; Boleliy, V. F.; Skopenko, V. V. Z. Anorg. Allg. Chem.
1980, 468, 178.
(28) Skopenko, V. V.; Gerasimchuk, N. N.; Tyukhtenko, S. I.; Kohler, H.
Z. Anorg. Allg. Chem. 1986, 542, 65–70.
(29) (a) Sadikov, G. G.; Zub, Yu. L.; Skopenko, V. V.; Porai-Koshits,
M. A.; Nikolaev, V. P. Koord. Khim. 1984, 10, 1253. (b) Zub, Yu. L.
Synthesis and Properties of Several Lanthanide Coordination Com-
pounds with Tris(dimethylamino)phosphinoxide, HMPA. Ph.D. Dis-
sertation, Chemistry Department, Kiev State University, Kiev, Ukraine,
1982.
(30) Zub, Yu. L.; Sadikov, G. G.; Skopenko, V. V.; Porai-Koshits, M. A.;
Nikolaev, V. P. Koord. Khim. 1985, 11, 532.
(31) Korecz, L.; Ko¨hler, H.; Neef, L. J. Organomet. Chem. 1974, 69, 105.
(21) (a) Reichardt, C. SolVents and SolVent Effects in Organic Chemistry,
3rd ed.; Wiley-VCH: Weinheim, Germany, 2003; p 629 and references
therein. (b) Bakhsiev, N. G., Ed. SolVatochromism: Problems and
Methods; Izd-vo Leningradskogo Universiteta: Leningrad, USSR,
1989; Chem. Abstr. 1990, 112, 186279g.
(22) Maher, T. Synthesis, Characterization and Anti-Cancer Properties of
Organotin(IV) Cyanoximates. M.S. Thesis, Department of Chemistry,
Southwest Missouri State University, Springfield, MO, 2004.
2380 Inorganic Chemistry, Vol. 48, No. 6, 2009

MonoWalent K, Cs, Tl, and Ag Nitrosodicyanomethanides
Figure 13. Change in Ag{ONC(CN)2} surface color as the result of exposure to a variety of gases: A, 60 min of exposure to visible light; B, immediately
after photoluminescence measurements (white arrow indicates beam area), and C, 30 min exposure to visible light. An example of interaction with nitrous
oxide (NO) is shown.
wavelength UV radiation (λmax ) 254 nm) emitted by a low-
pressure Hg lamp. We selected conventional light-sensitive,
inorganic silver(I) compounds, such as AgNO3 and AgCl,
to compare with covalent silver(I) nitrosodicyanomethanide.
Results of prolonged UV irradiation in open air are shown
in Figure 10 and confirm a great stability of the
Ag{ONC(CN)2} complex to the treatment, during which 81
J of energy was absorbed by 1 cm2 surface area (∼25 mg)
of the sample, leading to a rather small and insignificant color
change as compared to control compounds. Exposure of this
complex to gaseous olefins, carbon monoxide, hydrogen and
nitrous oxide leads to a dramatic change in its photostability
and is discussed below.
Solid-State Photoluminescence of Ag and Tl Complexes
in the Presence of Gases. Samples of solid Tl{ONC(CN)2}
as fine powders were treated with a variety of gases to
investigate their effect on the emissiveness of the complex.
The thallium atom in this compound, according to X-ray
analysis, is not coordinately saturated and therefore can
interact with other molecules. Nevertheless, exposure of
Tl{ONC(CN)2} to H2, SO2, NH3, NO, CO, C2H2, and C2H4
did not result in any appreciable change in its photolumi-
nescence. A completely different story was observed when
samples of dry Ag{ONC(CN)2} were treated with the above
pure gases. Thus, NH3 quickly, within seconds, irreversibly
quenches complex the photoluminescence, whereas SO2
interacts with Ag{ONC(CN)2} very slowly, leading to an
∼8% decrease in the PL intensity, leaving the spectroscopic
profile intact. Gases such as H2, NO, CO, C2H2, and C2H4
do interact with silver(I) nitrosodicyanomethanide, which is
reflected in the irreversible decrease of the photolumines-
cence intensity (Figures 11 and 12). The most striking feature
of such interactions is that the surface of Ag{ONC(CN)2}
now becomes sensitized toward visible light, and the complex
quickly changes color from bright yellow to dark brown.
The gas was pumped out of the cell, which was filled with
air prior to opening, and then the sample holder with
Ag{ONC(CN)2} was removed and exposed to light (Figures
10 and 13). Thus, within minutes, the compound exhibits a
pronounced color change and darkening after treatment with
one of the above gases (Figures 10B and 13). The effect of
studied gases is only on the sample’s surface since its
scratching reveals the original bright yellow color. That
implies sorption of the gas with chemical modification of
the surface due to the formation of a complex, as we suggest
in Figure 13. A chemical reaction with the surface is
supported by repeated pumping of the cell for ∼10 min to
remove gases that might have been left inside due to physical
sorption. The cell was filled with dry air prior to opening
and sample exposure to visible light. Acetylene is better than
ethylene sensitizer since it induces faster color change/
darkening on the Ag{ONC(CN)2} sample surface, which was
exposed after C2H2 treatment to visible light. This observation
is in agreement with the well-established knowledge in orga-
nometallic chemistry, that is, the much better π-accepting ability
of acetylene as compared to ethylene,36 and indirectly supports
the formation of π complexes between olefins and Ag(I).
Overall, this finding can be utilized for the development
of a battery-less, nonelectric sensor for the detection of H2,
CO, and gaseous olefins such as C2H2 and C2H4, which all
(32) (a) Sidman, J. W. J. Am. Chem. Soc. 1957, 2669–2675. (b) Sidman,
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Inorg. Nucl. Chem. 1968, 4, 133–136. (d) Feuer, H., Ed. The Chemistry
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Inorganic Chemistry, Vol. 48, No. 6, 2009 2381

Glover et al.
are large-scale industry products. The latter two gases are
flammable and frequently carried/delivered via pipe lines,
so the optical detection of leaks represents an important safety
issue. Ethylene, for example, is widely used in greenhouses
and for ripening vegetables in containers, and is consumed
in hundreds of ton quantities. Gaseous hydrogen, in turn, is
thought to be one of the leading fuels for motor vehicles in
the future due to its clean, “green” burning to water.
Therefore, battery-less, non-electrical methods of monitoring
of H2 in close compartments becomes increasingly important.
Discussed in this work, inexpensive and easy to prepare
silver(I) nitrosodicyanomethanide that possesses sensoric
properties might be a better alternative to apparently more
costly palladium compounds recently reported by Laguna.37
In summary, Ag{ONC(CN)2} demonstrates years-long sta-
bility toward visible light, which is a very convenient
property in view of the compound’s color change/darkening
only after exposure to gaseous H2, NO, CO, C2H2, and C2H4.
revealed a bathochromic shift in the band’s position depend-
ing on the atomic number of the metal ion in the compound.
This is the first observation of that kind of a correlation
between electronic π f π*, n f π*, and n* f π* transitions
and the number of electrons possessed by the metal center.
All three M(CCO) complexes exhibit ligand-based photo-
luminescence, observed as two broad bands at ∼370 and
∼500 nm upon excitation of solid samples in the UV region
at 300 nm. However, the Tl(I) complex clearly demonstrated
metal-based photoluminescence detected as a structured band
in the range of 680-800 nm. Silver(I) nitrosodicya-
nomethanide Ag{ONC(CN)2} was found to be UV-light- and
visible-light-insensitive for a prolonged period of time, but
it changes color and darkens while exposed to gases such as
H2, CO, NO, C2H2, and C2H4, followed by exposure to visible
light. The observed photosensitization of this complex can
be used in the development of nonelectric, battery-less
sensors with a variety of applications.
Conclusion
Acknowledgment. N.G. is grateful to Mr. Robert Holmes
for his help with photoluminescence measurements, Prof.
Sergey Lindeman for teaching practical crystallography, and
Prof. Vladimir Amirkhanov for technical support. G.G. and
N.G. thank the Cottrell College Research Corporation for
providing financial support for this work with Award CC
6598.
We report the preparation, spectroscopic properties, and
the structures of three new heavy metal complexes (Ag, Cs,
and Tl(I)) of nitrosodicyanomethanide, in which the anion
acts as a multidentate bridging ligand. Despite an analogous
1:1 stoichiometry, crystal structures of all three compounds
are completely different and represent 3D coordination
polymers of diverse complexity. The silver(I) compound
forms a covalent network in which the anion is tetracoor-
dinated via three nitrogen atoms (two of the CN groups and
one of the nitroso group) and the oxygen atom of the nitroso
group, with the central atom in a distorted tetrahedral
surrounding. The thallium(I) compound is positioned between
covalent and ionic structures; the central atom has four bonds
shorter than the sum of the ionic radii of Tl-N and Tl-O
and two longer electrostatic contacts. The 6s2 pair of Tl(I)
is stereoactive and affects the structure of the coordination
polyhedron, which is best described as a distorted square
pyramid. The cesium complex is ionic, and the metal center
has 10 contacts below 3.7 Å, of which 6 are shorter than
3.4 Å, and its structure represents an irregular polyhedron.
Diffusion reflectance spectra of studied solid, monovalent
nitrosodicyanomethanides in the range of 350-900 nm
Supporting Information Available: Experimental setup for
solid-state, room temperature photoluminescence measurements
(S1); special cell for solid-state PL measurements in the presence
of different gaseous substances (S2); methods of generation of small
quantities of dry, pure gases (S3); experimental setup for testing
of the UV-light stability of powdery, solid samples (S4); organiza-
tion of 2D polymeric sheets in the structure of Ag{ONC(CN)2}
(S5); geometry of the coordination polyhedron in the structure of
Ag{ONC(CN)2} (S6); geometry of the coordination polyhedron in
the structure of Cs{ONC(CN)2} (S7); structure of the coordination
Tl(I) polyhedron (S8); fragments of the polymeric structure of
Tl{ONC(CN)2} (S9); bond length and IR frequency relationships
(S10); total line-shape analysis of solid-state, UV-visible reflec-
tance spectra for K{ONC(CN)2}, Ag{ONC(CN)2}, and Tl{ONC-
(CN)2} (S11-S13); plots showing bathochromic shifts of bands in
the solid-state, UV-visible reflectance spectra of M{ONC(CN)2}
(S14); line-shape analysis of Tl{ONC(CN)2} and room temperature
PL at several excitation wavelengths (S15-S18); crystallographic
data for the structures of Ag{ONC(CN)2}, Cs{ONC(CN)2}, and
Tl{ONC(CN)2}. This material is available free of charge via the
Internet at http://pubs.acs.org.
(37) Cabanillas-Galan, P.; Farmer, L.; Hagan, T.; Nieuwenhuyzen, M.;
James, S. L.; Lagunas, C. M. Inorg. Chem. 2008, 47, 9035.
(38) Emsley, J. The Elements; Clarendon Press: Oxford, U.K., 1991.
(39) (a) Glaser, J. In AdVances in Inorganic Chemistry; Sykes, A. J., Ed.;
Academic Press: San Diego, 1995; Vol. 43, p 1. (b) Heydlauf, H.
Eur. J. Pharmacol. 1969, 6, 340.
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