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Hydrothermal synthesis and characterization of Zn(II), Cd(II) and Ag(I)-saccharinate complexes containing bis(imidazol) derivatives
Polyhedron 98 (2015) 180–189
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Hydrothermal synthesis and characterization of Zn(II), Cd(II) and Ag(I)-saccharinate complexes containing bis(imidazol) derivatives Hakan Erer a, Samet Karaçam a, Mürsel Arıcı a, Okan Zafer Yesßilel a,⇑, Ömer Çelik b a b
Department of Chemistry, Faculty of Arts and Sciences, Eskisßehir Osmangazi University, 26480 Eskisßehir, Turkey Department of Physics, Education Faculty, Dicle University, 21280 Diyarbakır, Turkey
a r t i c l e
i n f o
Article history: Received 23 January 2015 Accepted 7 June 2015 Available online 15 June 2015 Keywords: Saccharinate complexes d10 complexes Bis(imidazole) ligands (C H) Ag interactions Supramolecular complexes
a b s t r a c t Five mixed-ligand complexes, namely [Zn(sac)2(l-obix)]n (1), {[Cd(sac)2(l-obix)2]2H2O}n (2), [Cd(sac)2(l-pbix)(H2O)2]n (3), [Ag2(sac)2(l-pbix)2] (4) and [Ag2(sac)2(l-mbix)] (5) with saccharinate (sac) and three isomeric bis(imidazole) ligands (1,x-bis(imidazol-1-ylmethyl)benzene; x = 2, obix; x = 3, mbix and x = 4, pbix), have been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. Moreover, their thermal and photoluminescence properties have been studied in detail. Single crystal X-ray results show that the saccharinate ligand coordinates to the metal ions through nitrogen atoms in complexes 1 and 3–5, while it connects to the metal ion by the carbonyl oxygen atom in complex 2. Complexes 4 and 5 are dinuclear, while complexes 1–3 are 1D coordination polymers. In complexes 1–5, adjacent 1D chains are interlinked into a 3D network by hydrogen bonding, C–H p and p p interactions. The most striking features of complexes 4 and 5 are that they contain (C H) Ag and (C@O) Ag close interactions. Complexes 3–5 display blue emissions which are due to ligand to metal charge transfers. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Recently, the design and synthesis of supramolecular coordination polymers have attracted interest not only because of their applications, e.g. for gas adsorption, catalysis, magnetism, luminescence and biological activity, but also due to their fascinating structures [1–6]. In the construction of supramolecular architectures, the design and selection of organic ligands have a key role in the self assembly process. Moreover, non-covalent interactions, e.g. hydrogen-bonding, p p stacking and C–H p interactions, play a crucial role in the self-assembly processes of polymeric structures [7–10]. Although general non-covalent interactions (hydrogen-bonding, p p stacking and C–H p interactions) are widely seen in complexes, special (C H) Ag and (C@O) Ag close interactions are scarcely seen [8]. In recent years, the approach of mixed-ligand assembly has been effective in the construction of supramolecular structures [11,12]. In the mixed-ligand strategy, –N and –O donor ligands have been widely used [12]. In this study, three isomers of bis(imidazol-1-ylmethyl)benzene (an N-donor polymeric ligand) were used as neutral ligands in the syntheses of complexes. Bis(imidazol-1-ylmethyl)benzene (bix) ligands, with two –CH2– groups which allow bending and free rotation, can ⇑ Corresponding author. Tel.: +90 2222393750; fax: +90 2222393578. E-mail address: [email protected] (O.Z. Yesßilel). http://dx.doi.org/10.1016/j.poly.2015.06.011 0277-5387/Ó 2015 Elsevier Ltd. All rights reserved.
exhibit diverse conformations [13]. Furthermore, anionic ligands (–N or –O donor) have been utilized to ensure neutralization of the metal ions. Saccharinate, which is a prominent versatile ligand, has been widely utilized in the syntheses of mixed-ligand complexes as an anionic ligand [8,14]. It has several potential donor atoms, namely one carbonyl oxygen, one imino nitrogen and two sulfonyl oxygen atoms, to coordinates to metal ions with different coordination modes [15]. Moreover, the syntheses of d10 metal complexes have attracted attention due to their luminescence properties [16]. In this work, five d10 metal (Zn(II), Cd(II) and Ag(I)) complexes, namely [Zn(sac)2(1,2-bix)]n (1), {[Cd(sac)2 (m-obix)2]2H2O}n (2), [Cd(sac)2(m-pbix)(H2O)2]n (3), [Ag2(sac)2 (m-pbix)2] (4) and [Ag2(sac)2(m-mbix)] (5), were synthesized with three isomeric bis(imidazol-1-ylmethyl)benzene and sac ligands, and were characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Moreover, their thermal analysis and photoluminescence properties were investigated in detail. 2. Experimental 2.1. Materials and measurements All the chemicals were analytical reagent grade and used without further purification. The bix derivative ligands were synthesized according to the literature [17]. The IR spectra were
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recorded with a Bruker Tensor 27 FT–IR spectrometer using KBr pellets in the range 400–4000 cm 1. Elemental analyses (C, H, N and S) were performed with a Perkin-Elmer 2400C Elemental Analyzer. Thermal analyses (TG/DTA) were performed with a Perkin Elmer Diamond TG/DTA Thermal Analyzer at a heating rate of 10 °C min 1 in a static atmosphere in the temperature range 30–800 °C. The photoluminescence spectra for the solid complex samples were recorded on a Perkin-Elmer LS-55 Fluorescence spectrometer. Diffraction data for 1 and 2 were collected on an Agilent SuperNova diffractometer at 293 K; diffraction data for 3, 4 and 5 were collected on a Bruker APEXII CCD area-detector diffractometer at 296 K. The structures were solved by direct methods using the programs OLEX2 [18] and SHELXS-97 [19] with anisotropic thermal parameters for all non-hydrogen atoms. All non-hydrogen atoms were refined anisotropically by full-matrix least-squares methods using SHELXL-97 [19]. Molecular drawings were obtained using MERCURY [20]. Crystal data and structure refinement parameters for the complexes are presented in Table 1. Selected bond lengths, angles and hydrogen bonding geometries are listed in Tables 2 and 3. 2.2. Synthesis of the complexes 2.2.1. [Zn(sac)2(l-obix)]n (1) A mixture of Na(sac)H2O (0.99 g, 4.83 mmol) and ZnSO47H2O (0.43 g, 2.41 mmol) was stirred in water (20 mL) at 70 °C for 30 min and then obix (0.578 g, 2.41 mmol) was added to the mixture. The mixture was placed in a Pyrex bottle and heated at 120 °C for 96 h to obtain colorless crystals. Yield: 0.548 g, 34% (based on ZnSO47H2O). Anal. Calc. for C28H22N6O6S2Zn: C, 50.34; H, 3.32; N, 12.58; S, 9.60. Found: C, 49.30; H, 3.30; N, 12.48; S, 9.08%. IR (KBr, cm 1): 3128 (m), 3061 (w), 2962 (w), 1687 (s), 1670 (s), 1531 (m), 1514 (vs), 1454 (m), 1298 (vs), 1248 (s), 1153 (vs), 1109 (s), 954 (s), 761 (m), 678 (m). 2.2.2. {[Cd(sac)2(l-obix)2]2H2O}n (2) Complex 2 was synthesized following a procedure similar to that of complex 1, except that Cd(SO4)28/3H2O (0.619 g, 2.1 mmol) was used instead of ZnSO47H2O. Colorless crystals of 2 were
obtained. Yield: 0.668 g, 28% (based on Cd(SO4)28/3H2O). Anal. Calc. for C42H40N10O8S2Cd: C, 50.99; H, 4.08; N, 14.16; S, 6.48. Found: C, 51.89; H, 4.19; N, 13.95; S, 6.69%. IR (KBr, cm 1): 3489 (vs), 3119 (m), 2961 (w), 1612 (s), 1570 (s), 1514 (m), 1514 (vs), 1454 (m), 1384 (m), 1259 (s), 1248 (s), 1149 (s), 939 (m), 752 (m), 661 (m).
2.2.3. [Cd(sac)2(l-pbix)(H2O)2]n (3) The synthetic procedure for 3 was similar to that of 2, except that obix was replaced by pbix (0.578 g, 2.41 mmol). After four days, colorless crystals of 3 were obtained. Yield: 1.12 g, 62% (based on Cd(SO4)28/3H2O). Anal. Calc. for C28H26N6O8S2Cd: C, 44.78; H, 3.49; N, 14.97; S, 8.54. Found: C, 44.11; H, 3.85; N, 13.36; S, 8.82%. IR (KBr, cm 1): 3483 (vs), 3126 (m), 2943 (vw), 1635 (s), 1583 (s), 1516 (s), 1452 (m), 1340 (m), 1265 (vs), 1147 (vs), 951 (s), 763 (s), 655 (m).
2.2.4. [Ag2(sac)2(l-pbix)2] (4) A mixture of Na(sac)H2O (0.495 g, 2.41 mmol) and AgNO3 (0.41 g, 2.41 mmol) was stirred in water (20 mL) at 70 °C for 30 min and then pbix (0.288 g, 1.20 mmol) was added to the mixture. The mixture was placed in a Pyrex bottle and heated at 120 °C for 96 h to obtain colorless crystals. Yield: 2.19 g, 43% (based on AgNO3). Anal. Calc. for C42H36N10O6S2Ag2: C, 47.74; H, 3.43; N, 13.26; S, 6.07. Found: C, 47.64; H, 3.45; N, 13.36; S, 5.43%. IR (KBr, cm 1): 3113 (s), 3018 (m), 2943 (m), 1656 (vs), 1587 (s), 1514 (vs), 1483 (w), 1267 (vs), 1240 (vs), 1145 (vs), 954 (vs), 833(s), 767 (s), 754 (s), 661 (s).
2.2.5. [Ag2(sac)2(l-mbix)] (5) The synthetic procedure for 5 was similar to that used for 4, except mbix (0.288 g, 1.20 mmol) was used instead of pbix. Yield: 0.967 g, 19% (based on AgNO3). Anal. Calc. for C28H22N6O6S2Ag2: C, 41.09; H, 2.71; N, 10.27; S, 7.84. Found: C, 41.18; H, 2.75; N, 10.35; S, 7.22%. IR (KBr, cm 1): 3117 (m), 3042 (vw), 2927 (v), 1655 (vs), 1587 (m), 1520 (m), 1452 (m), 1288 (vs), 1249 (s), 1147 (vs), 962 (s), 833(s), 785 (m), 651 (m).
Table 1 Crystal data and structure refinement parameters for complexes 1–5. Crystal data
1
2
3
4
5
Chemical formula Formula weight (g mol 1) Temperature (K) Wavelength (Å) Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (Mg m 3) Absorption coefficient (mm 1) h range (°) Measured reflections Independent reflections Observed reflections [I > 2r(I)] Final R indices (all data) Rint Goodness-of-fit (GOF) on F2 Dqmax (e Å 3) Dqmin (e Å 3)
C28H22N6O6S2Zn 668.01 293 (2) 0.71073 Mo Ka monoclinic P21/c 18.618(5) 7.995(5) 19.274(5) 90 97.930(5) 90 2842(2) 4 1.561 1.07 3.2–27.7 11 621 5797 2759 R1 = 0.069, wR2 = 0.101 0.079 0.95 0.43 0.39
C42H40N10O8S2Cd 989.36
C28H26N6O8S2Cd 751.07 296(2)
C42H36N10O6S2Ag2 1056.67
C28H22N6O6S2Ag2 818.38
triclinic P1 8.408 10.566 12.730 105.47 102.55 90.93 1060.6 1 1.549 0.68 3.3–27.7 7235 4226 2828 R1 = 0.088, wR2 = 0.234 0.070 1.06 2.45 1.42
monoclinic P21/c 10.4564(2) 9.7917(2) 29.6744(5) 90 98.882(1) 90 3001.81(10) 4 1.662 0.93 2.6–35.8 32 312 6113 5697 R1 = 0.024, wR2 = 0.060 0.022 1.11 0.29 0.33
triclinic P1 9.4152(15) 9.674(2) 11.732(2) 85.918(11) 89.046(9) 75.030(9) 1029.7(3) 1 1.704 1.12 2.7–31.4 12 256 4088 2434 R1 = 0.072, wR2 = 0.194 0.049 1.04 0.73 0.52
monoclinic P21/n 16.9224(4) 8.1166(2) 22.0512(5) 90 106.138(1) 90 2909.43(12) 4 1.868 1.54 2.5–27.4 16 535 6315 4957 R1 = 0.036, wR2 = 0.075 0.024 1.03 0.57 0.35
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Table 2 Selected bond lengths and angles for complexes 1–5 (Å, °). Complex 1 Zn1–N1 Zn1–N2 N1–Zn1–N2 N1–Zn1–N6i
1.985(4) 2.000(4) 112.2(2) 110.83(18)
Zn1–N3 Zn1ii–N6 N6i–Zn1–N2 N1–Zn1–N3
1.990(4) 1.988(4) 105.94(17) 109.84(17)
N6 –Zn1–N3 N3–Zn1–N2
109.9(2) 108.09(18)
Complex 2 Cd1–O1 Cd1–O1i O1–Cd1–O1i N4–Cd1–O1i N4–Cd1–O1 N4i–Cd1–O1i N4i–Cd1–O1
2.417(6) 2.417(6) 180.0 90.2(2) 89.8(2) 89.8(2) 90.2(2)
Cd1–N4 Cd1–N2i N4i–Cd1–N4 N4i–Cd1–N2 N4i–Cd1–N2i N4–Cd1–N2 N4–Cd1–N2i
2.313(6) 2.350(6) 180.0 92.7(2) 87.3(2) 87.3(2) 92.7(2)
Cd1–N2 Cd1–N4i N2–Cd1–O1 N2–Cd1–O1i N2i–Cd1–O1i N2i–Cd1–O1 N2–Cd1–N2i
2.350(6) 2.313(6) 95.6(2) 84.4(2) 95.6(2) 84.4(2) 180.0
Complex 3 Cd1–O1 Cd1–O2 O1–Cd1–O2 O1–Cd1–N1 O1–Cd1–N2 O2–Cd1–N1 O2–Cd1–N2
2.3392(14) 2.3607(16) 177.54(6) 88.16(6) 92.78(6) 90.22(6) 88.83(6)
Cd1–N1 Cd1–N3 N6i–Cd1–O1 N6i–Cd1–O2 N6i–Cd1–N1 N6i–Cd1–N2 N1–Cd1–N2
2.3894(17) 2.2910(16) 92.27(6) 89.63(6) 91.62(6) 88.51(6) 179.04(5)
Cd1–N2 Cd1–N6i N3–Cd1–O1 N3–Cd1–O2 N3–Cd1–N6i N3–Cd1–N1 N3–Cd1–N2
2.4105(16) 2.2936(15) 82.54(6) 95.71(6) 172.52(6) 93.58(6) 86.38(6)
Complex 4 Ag1–N1 N2–Ag1–N1
2.237(6) 127.7(2)
Ag1–N2 N2–Ag1–N5i
2.207(6) 115.0(2)
Ag1–N5i
2.274(7)
Complex 5 Ag1–N1 Ag2–N6 N2–Ag1–N1
2.125(2) 2.086(2) 170.84(10)
Ag1–N2
2.118(2)
Ag2–N5
2.093(2)
N6–Ag2–N5
172.74(10)
Symmetry codes: (i) x, y + 3/2, z 1/2 (ii) x, y + 3/2, z + 1/2 for 1; (i) x + 1, y + 1, z (ii) x, y z for 3; (i) x + 2, y + 1, z + 2 for 4; (i) x + 2, y, z (ii) x + 2, y + 3, z + 1 for 5.
3. Results and discussion 3.1. Characterization As seen in the synthesis section, the elemental analysis results are consisted with the assigned formulations. In the IR spectra of 2 and 3, the broad bands observed at 3489 and 3419 cm 1 are due to the m(O–H) stretching vibrations of water molecules. For 1–5, aromatic and aliphatic m(C–H) stretching vibrations are observed in the ranges 3128–3116 cm 1 and 2962–2943 cm 1, respectively. In the IR spectra of saccharinate complexes, –CO, –SO2 and –CNS groups are characteristic for saccharinate ligand. Strong bands observed between 1687 and 1612 cm 1 are attributed to the m(C@O) stretching vibrations of the sac ligand. The m(C@O) stretching vibrations of complexes 1–5 are observed at 1670, 1612, 1635, 1656 and 1655 cm 1. The high absorption bands are due to an N-bonded sac ligand where the carbonyl groups do not participate in coordination for complexes 1, 4 and 5 [21]. However, the m(C@O) stretching vibrations of complexes 2 and 3 are shifted to lower frequencies (1612 and 1635 cm 1). This situation may be due to hydrogen bonds or metal–carbonyl oxygen coordination. For complex 2, the X-ray result showed that the sac ligand is connected to the metal ion by the oxygen atom of the
Table 3 Hydrogen-bond parameters for complexes 2 and 3 (Å, °). D–H A
D–H
H A
D A
D–H A (°)
Complex 2 O4–H4A O2
0.85
2.07
2.848(8)
152
Complex 3 O1–H1B O7iii O1–H1A O3 O2–H2B O6
0.81(3) 0.80(3) 0.95(4)
2.00(4) 1.87(3) 1.79(4)
2.785(2) 2.633(3) 2.674(3)
161(3) 160(3) 153(3)
Symmetry code: (iii)
x + 1,
y,
z + 2.
1, z (iii) x, y + 1, z (iv)
Zn1–N6i i
x + 1,
y + 2,
z for 2; (i) x + 1, y
1.987(4)
1, z (ii) x
1, y + 1,
carbonyl group and a significant shift to lower frequency was observed in the IR spectrum. Although the m(C@O) stretching vibration of complex 3 shifted to lower frequency, the X-ray result showed that there was no coordination of the carbonyl oxygen atom of the sac ligand to the metal ion. This shifting is assigned to hydrogen bonding between the carbonyl oxygen atom of the sac ligand and a coordinated water molecule [22]. The characteristic asymmetric mas(SO2) and symmetric mas(SO2) stretching vibrations appeared in the ranges 1298–1249 and 1153–1147 cm 1, respectively [23]. Moreover, the bands observed between 1333 and 951 cm 1 are assigned to asymmetric and symmetric stretching vibrations of the CNS group of the sac ligand. 3.1.1. Description of the crystal structures 3.1.1.1. [Zn(sac)2(l-obix)]n (1). The molecular structure of complex 1, along with the atom labeling scheme, is given in Fig. 1, while selected bond lengths and angles are presented in Table 2. Complex 1 crystallizes in the monoclinic space group P21/c and the asymmetric unit contains one Zn(II) ion, two sac and one obix ligands. The Zn1 atom is four-coordinated by two nitrogen atoms (N3 and N6i) from two different obix ligands [Zn1– N3 = 1.990(4) Å and Zn1–N6i = 1.987(4) Å] and two nitrogen atoms (N1 and N2) from two different sac ligands [Zn1–N1 = 1.985(4) Å and Zn1–N2 = 2.000(4) Å], which provide the charge balance for the complex. These Zn–N bond distances are comparable to the corresponding bonds lengths in the literature [24–28]. Four-coordinate complexes may exhibit either tetrahedral or square planar geometries. The actual geometry of the complex can be determined by a four-coordinate index parameter s4 such that s4 = [360° (a + b)]/141°, where a and b are the two largest angles around the four-coordinated metal center. The four-coordinate index parameter s4 values range from 1.00 for an ideal tetrahedral geometry, to zero for an ideal square planar geometry [29]. The s4 parameter for complex 1 is 0.97 and it can be considered to have a slightly distorted tetrahedral geometry. The [Zn(sac)2] units are
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Fig. 1. The molecular structure of 1 showing the atom numbering scheme [(i) x,
y + 3/2, z
1/2; (ii) x,
y + 3/2, z + 1/2].
Fig. 2. 1D polymeric structure of 1 (C–H hydrogen atoms are omitted for clarity).
bridged by obix ligands to form a 1D polymeric structure, with a Zn1–Zn1i separation of 13.732 Å (Fig. 2). Adjacent 1D chains are interlinked into a network by C–H p interactions [(Cg1 = C2– C3–C4–C5–C6–C7), Cg1 H27 = 2.954 Å] (Fig. 3).
C4 H4 Cg2ii interactions (Cg2 = C12–C13–C14–C15–C16–C17, C4 Cg2ii = 3.672(8) Å, H4 Cg2ii = 2.78 Å, C4 H4 Cg2ii = 162 °, where (ii) = 1 x, 2 y, 1 z).
3.1.1.2. [Cd(sac)2(l-obix)2]2H2O}n (2). The crystal structure of 2, along with the atom labeling scheme, is shown in Fig. 4 and selected bond lengths, angles and hydrogen bonding interactions are given in Tables 2 and 3. The asymmetric unit of complex 2 contains half a Cd(II) ion, one obix ligand, one sac anion and one crystal water molecule. The Cd(II) ion has a slightly distorted octahedral coordination environment. As shown in Fig. 4, the equatorial plane is occupied by four nitrogen atoms from four symmetry related obix ligands, while the axial positions are occupied by oxygen atoms of symmetry related saccharinate ligands. The Cd– Osac bond distance of 2.417(6) Å is slightly longer than that observed in [Cd(sac)2(C6H7NO)2] [25], [Cd(sac)2(C6H15N3)2] [30] and cis-[Cd(sac)2(C4H11NO)2] [31], while the Cd–Nobix bond distances of 2.313(6) and 2.350(6) Å are similar to those of obix complexes of cadmium(II) [32]. The 1,2-bix ligand exhibits a bis(monodentate) coordination mode. In 2, neighboring Cd(II) ions are connected by obix ligands to form a 1D linear chain with a Cd Cd distance of 10.566 Å (Fig. 5) and then adjacent chains are further linked by O H O hydrogen bonding interactions to form a 2D layer (Fig. 6). Adjacent pairs of layers are further extended into a 3D supramolecular network by Cg1 Cg1i interactions between the phenyl rings (Cg1 = C2–C3–C4–C5–C6, Cg1 Cg1i = 3.855(5) Å, where (i) = 2 x, 1 y, 1 z) and
3.1.1.3. [Cd(sac)2(l-pbix)(H2O)2]n (3). Complex 3 was obtained when the pbix ligand was used instead of obix under a similar reaction system. Single-crystal X-ray analysis reveals that complex 3 crystallizes in the monoclinic P21/c space group and that the structure of 3 is a 1-D zigzag chain (Fig. 7). The asymmetric unit of 3 consists of one Cd(II) ion, two sac anions, one pbix and two aqua ligands. The Cd(II) ion adopts a distorted octahedral geometry and is coordinated by four nitrogen atoms from sac and pbix ligands in the equatorial plane and two aqua ligands in the axial positions. Unlike complex 2, the sac ligand is coordinated to the Cd(II) ion by the nitrogen atom. The Cd–Nsac bond distances are 2.3894(17) and 2.4105(16) Å and the Cd–Nimidazole bond distances are 2.2910(16) and 2.2936(15) Å [46]. The Cd–N distances agree with those found in other structurally characterized Cd(II) complexes with sac ligands [33–36]. The pbix ligand adopts a bis(monodentate) bridging coordination mode to connect a neighboring [Cd(sac)2(H2O)2] unit to form a 1D zigzag chain with a Cd(II) Cd(II) distance of 14.3253(3) Å (Fig. 7). These 1D chains in 3 are linked via hydrogen-bonding interactions between the aqua ligands and sulfonyl oxygen atoms, generating a 2D network (Fig. 8(a)). Adjacent 2D layers are further extended into a 3D supramolecular network by face-to-face p p interactions between the phenyl rings planes of the sac ligands (Cg1 = C9–
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Fig. 3. C–H p interactions in 1.
Fig. 4. The molecular structure of 2 showing the atom numbering scheme [(i) x,
C10–C11–C12–C13–C14) with a centroid–centroid separation of 3.5085(11) Å (Fig. 8(b)). 3.1.1.4. [Ag2(sac)2(l-pbix)2] (4). The crystal structure of 4, along with the atom labeling scheme, is shown in Fig. 9. The asymmetric unit of 4 consists of one Ag(I) ion, one sac and one pbix ligand (Fig. 9). Neighboring Ag(I) ions are bridged by an imidazole N atom
y + 3/2, z
1/2; (ii) x,
y + 3/2, z + 1/2].
from a pbix ligand to give a twenty-six membered dinuclear [Ag2(m-pbix)2] unit with an Ag1 Ag1 distance of 12.212(2) Å. As shown in Fig. 9, the Ag1 ion is three-coordinated and the distorted trigonal planar geometry is completed by N atoms from sac ligands with an Ag1–N1 bond distance of 2.237(6) Å. This Ag–N bond distance is comparable to the corresponding bonds lengths in the literature [23,37–42].
H. Erer et al. / Polyhedron 98 (2015) 180–189
Fig. 5. 1D coordination polymeric structure of 2 (C–H hydrogen atoms are omitted for clarity).
Fig. 6. 2D network generated by O–H O hydrogen bonds for 2.
Fig. 7. The crystal structure of 3 showing the atom numbering scheme.
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Fig. 8. (a) 2D network generated by O–H O hydrogen bonds (all 1,4-bix ligands are omitted for clarity) and (b) p p interactions creating a 3D framework in 3.
Fig. 9. The crystal structure of 4 showing the atom numbering scheme.
Adjacent dinuclear units are linked by (C H) Ag1 and (C@O) Ag1 close interactions to generate a 2D network (Fig. 10), and these interactions are very important in generating a supramolecular structure. The Ag1 H21, Ag1 C21 bond distances and C21–H21 Ag1 bond angle are 2.903, 3.113(9) Å and 94.3°, respectively. This type of interaction is defined as the interaction of a pseudo-agostic (IPA) by Braga et al. [43]
[d(Ag H) d(Ag C) and C–H Ag < 100°]. In the (C1@O1) Ag1 interaction, the Ag1 O1 and Ag1 C1 bond distances are 3.284(6) and 3.301(8) Å, respectively and C1@O1 Ag1 bond angle is 80.08°. Until now, these weak close interactions have rarely been reported [43]. Moreover, there are intermolecular p p stacking interactions between both aromatic rings (phenyl: C2, C3, C4, C5, C6, C7
H. Erer et al. / Polyhedron 98 (2015) 180–189
187
Fig. 10. The intermolecular (C–H) Ag, (C@O) Ag, C–H p and p p interactions of 4.
Fig. 11. The crystal structure of 5 showing the atom numbering scheme.
Fig. 12. View of the (C H) Ag1, (C@O) Ag1 and Ag Ag interactions of 5.
(Cg1); imidazole: N2, C8, C9, N3, C10 (Cg2) and N4, C19, C20, N5, C21 (Cg3); Cg1 Cg1 = 3.807(5) and Cg2 Cg3 = 3.786(5) Å). In addition, there are also C–H p interactions between the C5–H5 group of the sac ligand and the benzene ring (Cg4) of the 1,4-bix ligand [H5 Cg4 = 2.954 Å]. These 2D networks are further extended into a 3D framework through weak C–H O hydrogen bonding interactions. 3.1.1.5. [Ag2(sac)2(l-mbix)] (5). Complex 5 was synthesized when the mbix ligand was used instead of pbix under similar reaction conditions. Each Ag(I) ion is two-coordinate with a slightly distorted linear coordination geometry (Fig. 11). Similar to complex 4, the mbix ligand is also coordinated to an adjacent Ag(I) ion as a bridging ligand to give a dinuclear unit. The sac ligands are
coordinated to the Ag1 and Ag2 centers through nitrogen atoms with an Ag1–N1 distance of 2.125(3) Å and Ag2–N6 distance of 2.086(3) Å. These bond distances are similar to those of other sac complexes of silver(I) [21,22,44–50]. The crystal packing of 5 is achieved by Ag Ag, (C H) Ag, (C@O) Ag and C–H p interactions to generate a threedimensional supramolecular network (Fig. 12). Adjacent dinuclear units are connected to each other through ligand unsupported weak Ag Ag interactions with an Ag2 Ag2 distance of 3.4303(3) Å, which is slightly shorter than twice the van der Waals radii of the Ag atom (3.44 Å). This interaction is known as an argentophilic interaction [51–57]. Similar to complex 4, there are intermolecular (C H) Ag1 and (C@O) Ag1 interactions (Ag1 H27 = 3.105, Ag1 C27 = 3.244(3) Å and
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Fig. 13. Photoluminescence spectra of 1–5 and Na(sac)H2O.
C27–H27 Ag1 = 92.07°; Ag1 O1 = 2.979(2), Ag1 C1 = 3.402(3) Å and C1 = O1 Ag1 = 99.4(2)°). Moreover, there are C–H p interactions between the C26–H26 unit of the sac ligand and the benzene ring (Cg1) of the mbix ligand [Cg1 = C12, C13, C14, C15, C16, C17, H26 Cg1 = 2.83, C26 Cg1 = 3.541(4) Å and C26 H26 Cg1 = 130(2)°].
characterized. The sac ligand exhibited two coordination modes in the complexes. The Zn(II) and Cd(II) complexes with the bis(imidazole) ligands had polymeric structures while Ag(I) complexes were dinuclear complexes. Photoluminescence spectra showed that complexes 3–5 exhibited blue luminescence which could be beneficial in optical devices.
3.2. Photoluminescent and thermal properties
Acknowledgements
The photoluminescence properties of the d10 complexes and Na(sac)H2O were investigated in the solid state under the same condition at room temperature (Fig. 13). Na(sac)H2O exhibits an emission at 537 nm upon excitation at 379 nm. The emission band of Na(sac)H2O is attributed to p⁄ ? n and p⁄ ? p transitions. As seen in Fig. 13, emission bands are observed at 436 and 537 nm for 1, 529 nm for 2, 438 nm for 3, 446 and 526 nm for 4 and 446 and 520 nm for 5 upon excitation at 379 nm. It is suggested that the photoluminescent properties of complexes 1 and 2 may be assigned to intraligand transitions of the coordinated sac ligand [8]. For 3–5, the emissions shifted blue when compared to Na(sac)H2O. These emissions may be attributed to ligand-to-metal charge-transfer (LMCT) or metal-to-ligand charge-transfer (MLCT) transitions [58]. Thermal analyses were carried out in the temperature range 30–800 °C in a static air atmosphere in order to evaluate the thermal stabilities and thermal behaviors of complexes 1–5 (Figs. S1–S5). Complexes 1 and 4 are stable up to 330 and 284 °C, respectively. For 2 and 3, The first weight losses of 2.66% in the temperature range 33–180 °C and 3.37% in the temperature range 86–157 °C correspond to release of lattice and coordinated water molecules, respectively (calcd. 3.63% for 2; calcd. 4.79% for 3). After the dehydration stages, complexes 2 and 3 are stable up to 220 and 271 °C. There is a slow weight loss for complex 5 up to 270 °C. Above those temperatures, the complexes begin to decompose with endothermic and exothermic peaks. The final residual products are possibly ZnO for 1 (found: 11.72%, calcd. 12.12%), CdO for 2 (found: 13.80%, calcd. 12.98%), CdO for 3 (found: 14.97%, calcd. 14.91%), AgO for 4 (found: 21.43%, calcd. 23.46%) and 5 (found: 15.84%, calcd. 15.16%).
This work was supported by the Scientific Research Fund of Eskisßehir Osmangazi University. Project number: 201319D17.
4. Conclusion Five novel d10 metal complexes containing three isomeric bis(imidazole) ligands and the sac anion were synthesized and
Appendix A. Supplementary data CCDC 1044810–1044814 contain the supplementary crystallographic data for complexes 1–5, respectively. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.poly.2015.06.011. References [1] N.L. Rosi, J. Eckert, M. Eddaoudi, D.T. Vodak, J. Kim, M. O’Keeffe, O.M. Yaghi, Science 300 (2003) 1127. [2] S.P. Velaga, S. Basavoju, D. Boström, J. Mol. Struct. 889 (2008) 150. [3] B. Gomez-Lor, E. Gutierrez-Puebla, M. Iglesias, M. Monge, C. Ruiz-Valero, N. Snejko, Inorg. Chem. 41 (2002) 2429. [4] Z. Xu, W. Meng, H. Li, H. Hou, Y. Fan, Inorg. Chem. 53 (2014) 3260. [5] Z. Adiguzel, A.T. Baykal, O. Kacar, V.T. Yilmaz, E. Ulukaya, C. Acilan, J. Proteome Res. 13 (2014) 5240. [6] M.D. Santana, R. García-Bueno, G. García, G. Sánchez, J. García, A.R. Kapdi, M. Naik, S. Pednekar, J. Pérez, L. García, Dalton Trans. 41 (2012) 3832. [7] G. Guilera, J.W. Steed, Chem. Commun. (1999) 1563. [8] O.Z. Yesßilel, B. Karamahmut, F. Semerci, Y. Yesßilöz, Polyhedron 42 (2012) 307. [9] G.A. Jeffrey, An Introduction to Hydrogen Bonding, Oxford University Press, New York, 1997. [10] Y.-Z. Zheng, M. Speldrich, P. Kögerler, X.-M. Chen, CrystEngComm 12 (2010) 1057. [11] M. Du, C.-P. Li, C.-S. Liu, S.-M. Fang, Coord. Chem. Rev. 257 (2013) 1282. [12] Z.Y. Fu, X.T. Wu, J.C. Dai, S.M. Hu, W.X. Du, H.H. Zhang, R.Q. Sun, T. Eur, J. Inorg. Chem. 2002 (2002) 2730. [13] Z.-Z. Shi, L.-F. Ma, X.-J. Wu, F.-F. Li, Synth. React. Inorg. M. 44 (2014) 598. [14] E. Guney, V.T. Yilmaz, O. Buyukgungor, Polyhedron 29 (2010) 1437. [15] E.J. Baran, V.T. Yilmaz, Coord. Chem. Rev. 250 (2006) 1980. [16] F.-F. Yang, X.-Y. Yu, Y.-H. Luo, X.-F. Wang, D.-H. Sun, H. Zhang, Polyhedron 85 (2015) 337.
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Hydrothermal synthesis and characterization of Zn(II), Cd(II) and Ag(I)-saccharinate complexes containing bis(imidazol) derivatives Hakan Erer a, Samet Karaçam a, Mürsel Arıcı a, Okan Zafer Yesßilel a,⇑, Ömer Çelik b a b
Department of Chemistry, Faculty of Arts and Sciences, Eskisßehir Osmangazi University, 26480 Eskisßehir, Turkey Department of Physics, Education Faculty, Dicle University, 21280 Diyarbakır, Turkey
a r t i c l e
i n f o
Article history: Received 23 January 2015 Accepted 7 June 2015 Available online 15 June 2015 Keywords: Saccharinate complexes d10 complexes Bis(imidazole) ligands (C H) Ag interactions Supramolecular complexes
a b s t r a c t Five mixed-ligand complexes, namely [Zn(sac)2(l-obix)]n (1), {[Cd(sac)2(l-obix)2]2H2O}n (2), [Cd(sac)2(l-pbix)(H2O)2]n (3), [Ag2(sac)2(l-pbix)2] (4) and [Ag2(sac)2(l-mbix)] (5) with saccharinate (sac) and three isomeric bis(imidazole) ligands (1,x-bis(imidazol-1-ylmethyl)benzene; x = 2, obix; x = 3, mbix and x = 4, pbix), have been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. Moreover, their thermal and photoluminescence properties have been studied in detail. Single crystal X-ray results show that the saccharinate ligand coordinates to the metal ions through nitrogen atoms in complexes 1 and 3–5, while it connects to the metal ion by the carbonyl oxygen atom in complex 2. Complexes 4 and 5 are dinuclear, while complexes 1–3 are 1D coordination polymers. In complexes 1–5, adjacent 1D chains are interlinked into a 3D network by hydrogen bonding, C–H p and p p interactions. The most striking features of complexes 4 and 5 are that they contain (C H) Ag and (C@O) Ag close interactions. Complexes 3–5 display blue emissions which are due to ligand to metal charge transfers. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Recently, the design and synthesis of supramolecular coordination polymers have attracted interest not only because of their applications, e.g. for gas adsorption, catalysis, magnetism, luminescence and biological activity, but also due to their fascinating structures [1–6]. In the construction of supramolecular architectures, the design and selection of organic ligands have a key role in the self assembly process. Moreover, non-covalent interactions, e.g. hydrogen-bonding, p p stacking and C–H p interactions, play a crucial role in the self-assembly processes of polymeric structures [7–10]. Although general non-covalent interactions (hydrogen-bonding, p p stacking and C–H p interactions) are widely seen in complexes, special (C H) Ag and (C@O) Ag close interactions are scarcely seen [8]. In recent years, the approach of mixed-ligand assembly has been effective in the construction of supramolecular structures [11,12]. In the mixed-ligand strategy, –N and –O donor ligands have been widely used [12]. In this study, three isomers of bis(imidazol-1-ylmethyl)benzene (an N-donor polymeric ligand) were used as neutral ligands in the syntheses of complexes. Bis(imidazol-1-ylmethyl)benzene (bix) ligands, with two –CH2– groups which allow bending and free rotation, can ⇑ Corresponding author. Tel.: +90 2222393750; fax: +90 2222393578. E-mail address: [email protected] (O.Z. Yesßilel). http://dx.doi.org/10.1016/j.poly.2015.06.011 0277-5387/Ó 2015 Elsevier Ltd. All rights reserved.
exhibit diverse conformations [13]. Furthermore, anionic ligands (–N or –O donor) have been utilized to ensure neutralization of the metal ions. Saccharinate, which is a prominent versatile ligand, has been widely utilized in the syntheses of mixed-ligand complexes as an anionic ligand [8,14]. It has several potential donor atoms, namely one carbonyl oxygen, one imino nitrogen and two sulfonyl oxygen atoms, to coordinates to metal ions with different coordination modes [15]. Moreover, the syntheses of d10 metal complexes have attracted attention due to their luminescence properties [16]. In this work, five d10 metal (Zn(II), Cd(II) and Ag(I)) complexes, namely [Zn(sac)2(1,2-bix)]n (1), {[Cd(sac)2 (m-obix)2]2H2O}n (2), [Cd(sac)2(m-pbix)(H2O)2]n (3), [Ag2(sac)2 (m-pbix)2] (4) and [Ag2(sac)2(m-mbix)] (5), were synthesized with three isomeric bis(imidazol-1-ylmethyl)benzene and sac ligands, and were characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Moreover, their thermal analysis and photoluminescence properties were investigated in detail. 2. Experimental 2.1. Materials and measurements All the chemicals were analytical reagent grade and used without further purification. The bix derivative ligands were synthesized according to the literature [17]. The IR spectra were
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recorded with a Bruker Tensor 27 FT–IR spectrometer using KBr pellets in the range 400–4000 cm 1. Elemental analyses (C, H, N and S) were performed with a Perkin-Elmer 2400C Elemental Analyzer. Thermal analyses (TG/DTA) were performed with a Perkin Elmer Diamond TG/DTA Thermal Analyzer at a heating rate of 10 °C min 1 in a static atmosphere in the temperature range 30–800 °C. The photoluminescence spectra for the solid complex samples were recorded on a Perkin-Elmer LS-55 Fluorescence spectrometer. Diffraction data for 1 and 2 were collected on an Agilent SuperNova diffractometer at 293 K; diffraction data for 3, 4 and 5 were collected on a Bruker APEXII CCD area-detector diffractometer at 296 K. The structures were solved by direct methods using the programs OLEX2 [18] and SHELXS-97 [19] with anisotropic thermal parameters for all non-hydrogen atoms. All non-hydrogen atoms were refined anisotropically by full-matrix least-squares methods using SHELXL-97 [19]. Molecular drawings were obtained using MERCURY [20]. Crystal data and structure refinement parameters for the complexes are presented in Table 1. Selected bond lengths, angles and hydrogen bonding geometries are listed in Tables 2 and 3. 2.2. Synthesis of the complexes 2.2.1. [Zn(sac)2(l-obix)]n (1) A mixture of Na(sac)H2O (0.99 g, 4.83 mmol) and ZnSO47H2O (0.43 g, 2.41 mmol) was stirred in water (20 mL) at 70 °C for 30 min and then obix (0.578 g, 2.41 mmol) was added to the mixture. The mixture was placed in a Pyrex bottle and heated at 120 °C for 96 h to obtain colorless crystals. Yield: 0.548 g, 34% (based on ZnSO47H2O). Anal. Calc. for C28H22N6O6S2Zn: C, 50.34; H, 3.32; N, 12.58; S, 9.60. Found: C, 49.30; H, 3.30; N, 12.48; S, 9.08%. IR (KBr, cm 1): 3128 (m), 3061 (w), 2962 (w), 1687 (s), 1670 (s), 1531 (m), 1514 (vs), 1454 (m), 1298 (vs), 1248 (s), 1153 (vs), 1109 (s), 954 (s), 761 (m), 678 (m). 2.2.2. {[Cd(sac)2(l-obix)2]2H2O}n (2) Complex 2 was synthesized following a procedure similar to that of complex 1, except that Cd(SO4)28/3H2O (0.619 g, 2.1 mmol) was used instead of ZnSO47H2O. Colorless crystals of 2 were
obtained. Yield: 0.668 g, 28% (based on Cd(SO4)28/3H2O). Anal. Calc. for C42H40N10O8S2Cd: C, 50.99; H, 4.08; N, 14.16; S, 6.48. Found: C, 51.89; H, 4.19; N, 13.95; S, 6.69%. IR (KBr, cm 1): 3489 (vs), 3119 (m), 2961 (w), 1612 (s), 1570 (s), 1514 (m), 1514 (vs), 1454 (m), 1384 (m), 1259 (s), 1248 (s), 1149 (s), 939 (m), 752 (m), 661 (m).
2.2.3. [Cd(sac)2(l-pbix)(H2O)2]n (3) The synthetic procedure for 3 was similar to that of 2, except that obix was replaced by pbix (0.578 g, 2.41 mmol). After four days, colorless crystals of 3 were obtained. Yield: 1.12 g, 62% (based on Cd(SO4)28/3H2O). Anal. Calc. for C28H26N6O8S2Cd: C, 44.78; H, 3.49; N, 14.97; S, 8.54. Found: C, 44.11; H, 3.85; N, 13.36; S, 8.82%. IR (KBr, cm 1): 3483 (vs), 3126 (m), 2943 (vw), 1635 (s), 1583 (s), 1516 (s), 1452 (m), 1340 (m), 1265 (vs), 1147 (vs), 951 (s), 763 (s), 655 (m).
2.2.4. [Ag2(sac)2(l-pbix)2] (4) A mixture of Na(sac)H2O (0.495 g, 2.41 mmol) and AgNO3 (0.41 g, 2.41 mmol) was stirred in water (20 mL) at 70 °C for 30 min and then pbix (0.288 g, 1.20 mmol) was added to the mixture. The mixture was placed in a Pyrex bottle and heated at 120 °C for 96 h to obtain colorless crystals. Yield: 2.19 g, 43% (based on AgNO3). Anal. Calc. for C42H36N10O6S2Ag2: C, 47.74; H, 3.43; N, 13.26; S, 6.07. Found: C, 47.64; H, 3.45; N, 13.36; S, 5.43%. IR (KBr, cm 1): 3113 (s), 3018 (m), 2943 (m), 1656 (vs), 1587 (s), 1514 (vs), 1483 (w), 1267 (vs), 1240 (vs), 1145 (vs), 954 (vs), 833(s), 767 (s), 754 (s), 661 (s).
2.2.5. [Ag2(sac)2(l-mbix)] (5) The synthetic procedure for 5 was similar to that used for 4, except mbix (0.288 g, 1.20 mmol) was used instead of pbix. Yield: 0.967 g, 19% (based on AgNO3). Anal. Calc. for C28H22N6O6S2Ag2: C, 41.09; H, 2.71; N, 10.27; S, 7.84. Found: C, 41.18; H, 2.75; N, 10.35; S, 7.22%. IR (KBr, cm 1): 3117 (m), 3042 (vw), 2927 (v), 1655 (vs), 1587 (m), 1520 (m), 1452 (m), 1288 (vs), 1249 (s), 1147 (vs), 962 (s), 833(s), 785 (m), 651 (m).
Table 1 Crystal data and structure refinement parameters for complexes 1–5. Crystal data
1
2
3
4
5
Chemical formula Formula weight (g mol 1) Temperature (K) Wavelength (Å) Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (Mg m 3) Absorption coefficient (mm 1) h range (°) Measured reflections Independent reflections Observed reflections [I > 2r(I)] Final R indices (all data) Rint Goodness-of-fit (GOF) on F2 Dqmax (e Å 3) Dqmin (e Å 3)
C28H22N6O6S2Zn 668.01 293 (2) 0.71073 Mo Ka monoclinic P21/c 18.618(5) 7.995(5) 19.274(5) 90 97.930(5) 90 2842(2) 4 1.561 1.07 3.2–27.7 11 621 5797 2759 R1 = 0.069, wR2 = 0.101 0.079 0.95 0.43 0.39
C42H40N10O8S2Cd 989.36
C28H26N6O8S2Cd 751.07 296(2)
C42H36N10O6S2Ag2 1056.67
C28H22N6O6S2Ag2 818.38
triclinic P1 8.408 10.566 12.730 105.47 102.55 90.93 1060.6 1 1.549 0.68 3.3–27.7 7235 4226 2828 R1 = 0.088, wR2 = 0.234 0.070 1.06 2.45 1.42
monoclinic P21/c 10.4564(2) 9.7917(2) 29.6744(5) 90 98.882(1) 90 3001.81(10) 4 1.662 0.93 2.6–35.8 32 312 6113 5697 R1 = 0.024, wR2 = 0.060 0.022 1.11 0.29 0.33
triclinic P1 9.4152(15) 9.674(2) 11.732(2) 85.918(11) 89.046(9) 75.030(9) 1029.7(3) 1 1.704 1.12 2.7–31.4 12 256 4088 2434 R1 = 0.072, wR2 = 0.194 0.049 1.04 0.73 0.52
monoclinic P21/n 16.9224(4) 8.1166(2) 22.0512(5) 90 106.138(1) 90 2909.43(12) 4 1.868 1.54 2.5–27.4 16 535 6315 4957 R1 = 0.036, wR2 = 0.075 0.024 1.03 0.57 0.35
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Table 2 Selected bond lengths and angles for complexes 1–5 (Å, °). Complex 1 Zn1–N1 Zn1–N2 N1–Zn1–N2 N1–Zn1–N6i
1.985(4) 2.000(4) 112.2(2) 110.83(18)
Zn1–N3 Zn1ii–N6 N6i–Zn1–N2 N1–Zn1–N3
1.990(4) 1.988(4) 105.94(17) 109.84(17)
N6 –Zn1–N3 N3–Zn1–N2
109.9(2) 108.09(18)
Complex 2 Cd1–O1 Cd1–O1i O1–Cd1–O1i N4–Cd1–O1i N4–Cd1–O1 N4i–Cd1–O1i N4i–Cd1–O1
2.417(6) 2.417(6) 180.0 90.2(2) 89.8(2) 89.8(2) 90.2(2)
Cd1–N4 Cd1–N2i N4i–Cd1–N4 N4i–Cd1–N2 N4i–Cd1–N2i N4–Cd1–N2 N4–Cd1–N2i
2.313(6) 2.350(6) 180.0 92.7(2) 87.3(2) 87.3(2) 92.7(2)
Cd1–N2 Cd1–N4i N2–Cd1–O1 N2–Cd1–O1i N2i–Cd1–O1i N2i–Cd1–O1 N2–Cd1–N2i
2.350(6) 2.313(6) 95.6(2) 84.4(2) 95.6(2) 84.4(2) 180.0
Complex 3 Cd1–O1 Cd1–O2 O1–Cd1–O2 O1–Cd1–N1 O1–Cd1–N2 O2–Cd1–N1 O2–Cd1–N2
2.3392(14) 2.3607(16) 177.54(6) 88.16(6) 92.78(6) 90.22(6) 88.83(6)
Cd1–N1 Cd1–N3 N6i–Cd1–O1 N6i–Cd1–O2 N6i–Cd1–N1 N6i–Cd1–N2 N1–Cd1–N2
2.3894(17) 2.2910(16) 92.27(6) 89.63(6) 91.62(6) 88.51(6) 179.04(5)
Cd1–N2 Cd1–N6i N3–Cd1–O1 N3–Cd1–O2 N3–Cd1–N6i N3–Cd1–N1 N3–Cd1–N2
2.4105(16) 2.2936(15) 82.54(6) 95.71(6) 172.52(6) 93.58(6) 86.38(6)
Complex 4 Ag1–N1 N2–Ag1–N1
2.237(6) 127.7(2)
Ag1–N2 N2–Ag1–N5i
2.207(6) 115.0(2)
Ag1–N5i
2.274(7)
Complex 5 Ag1–N1 Ag2–N6 N2–Ag1–N1
2.125(2) 2.086(2) 170.84(10)
Ag1–N2
2.118(2)
Ag2–N5
2.093(2)
N6–Ag2–N5
172.74(10)
Symmetry codes: (i) x, y + 3/2, z 1/2 (ii) x, y + 3/2, z + 1/2 for 1; (i) x + 1, y + 1, z (ii) x, y z for 3; (i) x + 2, y + 1, z + 2 for 4; (i) x + 2, y, z (ii) x + 2, y + 3, z + 1 for 5.
3. Results and discussion 3.1. Characterization As seen in the synthesis section, the elemental analysis results are consisted with the assigned formulations. In the IR spectra of 2 and 3, the broad bands observed at 3489 and 3419 cm 1 are due to the m(O–H) stretching vibrations of water molecules. For 1–5, aromatic and aliphatic m(C–H) stretching vibrations are observed in the ranges 3128–3116 cm 1 and 2962–2943 cm 1, respectively. In the IR spectra of saccharinate complexes, –CO, –SO2 and –CNS groups are characteristic for saccharinate ligand. Strong bands observed between 1687 and 1612 cm 1 are attributed to the m(C@O) stretching vibrations of the sac ligand. The m(C@O) stretching vibrations of complexes 1–5 are observed at 1670, 1612, 1635, 1656 and 1655 cm 1. The high absorption bands are due to an N-bonded sac ligand where the carbonyl groups do not participate in coordination for complexes 1, 4 and 5 [21]. However, the m(C@O) stretching vibrations of complexes 2 and 3 are shifted to lower frequencies (1612 and 1635 cm 1). This situation may be due to hydrogen bonds or metal–carbonyl oxygen coordination. For complex 2, the X-ray result showed that the sac ligand is connected to the metal ion by the oxygen atom of the
Table 3 Hydrogen-bond parameters for complexes 2 and 3 (Å, °). D–H A
D–H
H A
D A
D–H A (°)
Complex 2 O4–H4A O2
0.85
2.07
2.848(8)
152
Complex 3 O1–H1B O7iii O1–H1A O3 O2–H2B O6
0.81(3) 0.80(3) 0.95(4)
2.00(4) 1.87(3) 1.79(4)
2.785(2) 2.633(3) 2.674(3)
161(3) 160(3) 153(3)
Symmetry code: (iii)
x + 1,
y,
z + 2.
1, z (iii) x, y + 1, z (iv)
Zn1–N6i i
x + 1,
y + 2,
z for 2; (i) x + 1, y
1.987(4)
1, z (ii) x
1, y + 1,
carbonyl group and a significant shift to lower frequency was observed in the IR spectrum. Although the m(C@O) stretching vibration of complex 3 shifted to lower frequency, the X-ray result showed that there was no coordination of the carbonyl oxygen atom of the sac ligand to the metal ion. This shifting is assigned to hydrogen bonding between the carbonyl oxygen atom of the sac ligand and a coordinated water molecule [22]. The characteristic asymmetric mas(SO2) and symmetric mas(SO2) stretching vibrations appeared in the ranges 1298–1249 and 1153–1147 cm 1, respectively [23]. Moreover, the bands observed between 1333 and 951 cm 1 are assigned to asymmetric and symmetric stretching vibrations of the CNS group of the sac ligand. 3.1.1. Description of the crystal structures 3.1.1.1. [Zn(sac)2(l-obix)]n (1). The molecular structure of complex 1, along with the atom labeling scheme, is given in Fig. 1, while selected bond lengths and angles are presented in Table 2. Complex 1 crystallizes in the monoclinic space group P21/c and the asymmetric unit contains one Zn(II) ion, two sac and one obix ligands. The Zn1 atom is four-coordinated by two nitrogen atoms (N3 and N6i) from two different obix ligands [Zn1– N3 = 1.990(4) Å and Zn1–N6i = 1.987(4) Å] and two nitrogen atoms (N1 and N2) from two different sac ligands [Zn1–N1 = 1.985(4) Å and Zn1–N2 = 2.000(4) Å], which provide the charge balance for the complex. These Zn–N bond distances are comparable to the corresponding bonds lengths in the literature [24–28]. Four-coordinate complexes may exhibit either tetrahedral or square planar geometries. The actual geometry of the complex can be determined by a four-coordinate index parameter s4 such that s4 = [360° (a + b)]/141°, where a and b are the two largest angles around the four-coordinated metal center. The four-coordinate index parameter s4 values range from 1.00 for an ideal tetrahedral geometry, to zero for an ideal square planar geometry [29]. The s4 parameter for complex 1 is 0.97 and it can be considered to have a slightly distorted tetrahedral geometry. The [Zn(sac)2] units are
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Fig. 1. The molecular structure of 1 showing the atom numbering scheme [(i) x,
y + 3/2, z
1/2; (ii) x,
y + 3/2, z + 1/2].
Fig. 2. 1D polymeric structure of 1 (C–H hydrogen atoms are omitted for clarity).
bridged by obix ligands to form a 1D polymeric structure, with a Zn1–Zn1i separation of 13.732 Å (Fig. 2). Adjacent 1D chains are interlinked into a network by C–H p interactions [(Cg1 = C2– C3–C4–C5–C6–C7), Cg1 H27 = 2.954 Å] (Fig. 3).
C4 H4 Cg2ii interactions (Cg2 = C12–C13–C14–C15–C16–C17, C4 Cg2ii = 3.672(8) Å, H4 Cg2ii = 2.78 Å, C4 H4 Cg2ii = 162 °, where (ii) = 1 x, 2 y, 1 z).
3.1.1.2. [Cd(sac)2(l-obix)2]2H2O}n (2). The crystal structure of 2, along with the atom labeling scheme, is shown in Fig. 4 and selected bond lengths, angles and hydrogen bonding interactions are given in Tables 2 and 3. The asymmetric unit of complex 2 contains half a Cd(II) ion, one obix ligand, one sac anion and one crystal water molecule. The Cd(II) ion has a slightly distorted octahedral coordination environment. As shown in Fig. 4, the equatorial plane is occupied by four nitrogen atoms from four symmetry related obix ligands, while the axial positions are occupied by oxygen atoms of symmetry related saccharinate ligands. The Cd– Osac bond distance of 2.417(6) Å is slightly longer than that observed in [Cd(sac)2(C6H7NO)2] [25], [Cd(sac)2(C6H15N3)2] [30] and cis-[Cd(sac)2(C4H11NO)2] [31], while the Cd–Nobix bond distances of 2.313(6) and 2.350(6) Å are similar to those of obix complexes of cadmium(II) [32]. The 1,2-bix ligand exhibits a bis(monodentate) coordination mode. In 2, neighboring Cd(II) ions are connected by obix ligands to form a 1D linear chain with a Cd Cd distance of 10.566 Å (Fig. 5) and then adjacent chains are further linked by O H O hydrogen bonding interactions to form a 2D layer (Fig. 6). Adjacent pairs of layers are further extended into a 3D supramolecular network by Cg1 Cg1i interactions between the phenyl rings (Cg1 = C2–C3–C4–C5–C6, Cg1 Cg1i = 3.855(5) Å, where (i) = 2 x, 1 y, 1 z) and
3.1.1.3. [Cd(sac)2(l-pbix)(H2O)2]n (3). Complex 3 was obtained when the pbix ligand was used instead of obix under a similar reaction system. Single-crystal X-ray analysis reveals that complex 3 crystallizes in the monoclinic P21/c space group and that the structure of 3 is a 1-D zigzag chain (Fig. 7). The asymmetric unit of 3 consists of one Cd(II) ion, two sac anions, one pbix and two aqua ligands. The Cd(II) ion adopts a distorted octahedral geometry and is coordinated by four nitrogen atoms from sac and pbix ligands in the equatorial plane and two aqua ligands in the axial positions. Unlike complex 2, the sac ligand is coordinated to the Cd(II) ion by the nitrogen atom. The Cd–Nsac bond distances are 2.3894(17) and 2.4105(16) Å and the Cd–Nimidazole bond distances are 2.2910(16) and 2.2936(15) Å [46]. The Cd–N distances agree with those found in other structurally characterized Cd(II) complexes with sac ligands [33–36]. The pbix ligand adopts a bis(monodentate) bridging coordination mode to connect a neighboring [Cd(sac)2(H2O)2] unit to form a 1D zigzag chain with a Cd(II) Cd(II) distance of 14.3253(3) Å (Fig. 7). These 1D chains in 3 are linked via hydrogen-bonding interactions between the aqua ligands and sulfonyl oxygen atoms, generating a 2D network (Fig. 8(a)). Adjacent 2D layers are further extended into a 3D supramolecular network by face-to-face p p interactions between the phenyl rings planes of the sac ligands (Cg1 = C9–
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Fig. 3. C–H p interactions in 1.
Fig. 4. The molecular structure of 2 showing the atom numbering scheme [(i) x,
C10–C11–C12–C13–C14) with a centroid–centroid separation of 3.5085(11) Å (Fig. 8(b)). 3.1.1.4. [Ag2(sac)2(l-pbix)2] (4). The crystal structure of 4, along with the atom labeling scheme, is shown in Fig. 9. The asymmetric unit of 4 consists of one Ag(I) ion, one sac and one pbix ligand (Fig. 9). Neighboring Ag(I) ions are bridged by an imidazole N atom
y + 3/2, z
1/2; (ii) x,
y + 3/2, z + 1/2].
from a pbix ligand to give a twenty-six membered dinuclear [Ag2(m-pbix)2] unit with an Ag1 Ag1 distance of 12.212(2) Å. As shown in Fig. 9, the Ag1 ion is three-coordinated and the distorted trigonal planar geometry is completed by N atoms from sac ligands with an Ag1–N1 bond distance of 2.237(6) Å. This Ag–N bond distance is comparable to the corresponding bonds lengths in the literature [23,37–42].
H. Erer et al. / Polyhedron 98 (2015) 180–189
Fig. 5. 1D coordination polymeric structure of 2 (C–H hydrogen atoms are omitted for clarity).
Fig. 6. 2D network generated by O–H O hydrogen bonds for 2.
Fig. 7. The crystal structure of 3 showing the atom numbering scheme.
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Fig. 8. (a) 2D network generated by O–H O hydrogen bonds (all 1,4-bix ligands are omitted for clarity) and (b) p p interactions creating a 3D framework in 3.
Fig. 9. The crystal structure of 4 showing the atom numbering scheme.
Adjacent dinuclear units are linked by (C H) Ag1 and (C@O) Ag1 close interactions to generate a 2D network (Fig. 10), and these interactions are very important in generating a supramolecular structure. The Ag1 H21, Ag1 C21 bond distances and C21–H21 Ag1 bond angle are 2.903, 3.113(9) Å and 94.3°, respectively. This type of interaction is defined as the interaction of a pseudo-agostic (IPA) by Braga et al. [43]
[d(Ag H) d(Ag C) and C–H Ag < 100°]. In the (C1@O1) Ag1 interaction, the Ag1 O1 and Ag1 C1 bond distances are 3.284(6) and 3.301(8) Å, respectively and C1@O1 Ag1 bond angle is 80.08°. Until now, these weak close interactions have rarely been reported [43]. Moreover, there are intermolecular p p stacking interactions between both aromatic rings (phenyl: C2, C3, C4, C5, C6, C7
H. Erer et al. / Polyhedron 98 (2015) 180–189
187
Fig. 10. The intermolecular (C–H) Ag, (C@O) Ag, C–H p and p p interactions of 4.
Fig. 11. The crystal structure of 5 showing the atom numbering scheme.
Fig. 12. View of the (C H) Ag1, (C@O) Ag1 and Ag Ag interactions of 5.
(Cg1); imidazole: N2, C8, C9, N3, C10 (Cg2) and N4, C19, C20, N5, C21 (Cg3); Cg1 Cg1 = 3.807(5) and Cg2 Cg3 = 3.786(5) Å). In addition, there are also C–H p interactions between the C5–H5 group of the sac ligand and the benzene ring (Cg4) of the 1,4-bix ligand [H5 Cg4 = 2.954 Å]. These 2D networks are further extended into a 3D framework through weak C–H O hydrogen bonding interactions. 3.1.1.5. [Ag2(sac)2(l-mbix)] (5). Complex 5 was synthesized when the mbix ligand was used instead of pbix under similar reaction conditions. Each Ag(I) ion is two-coordinate with a slightly distorted linear coordination geometry (Fig. 11). Similar to complex 4, the mbix ligand is also coordinated to an adjacent Ag(I) ion as a bridging ligand to give a dinuclear unit. The sac ligands are
coordinated to the Ag1 and Ag2 centers through nitrogen atoms with an Ag1–N1 distance of 2.125(3) Å and Ag2–N6 distance of 2.086(3) Å. These bond distances are similar to those of other sac complexes of silver(I) [21,22,44–50]. The crystal packing of 5 is achieved by Ag Ag, (C H) Ag, (C@O) Ag and C–H p interactions to generate a threedimensional supramolecular network (Fig. 12). Adjacent dinuclear units are connected to each other through ligand unsupported weak Ag Ag interactions with an Ag2 Ag2 distance of 3.4303(3) Å, which is slightly shorter than twice the van der Waals radii of the Ag atom (3.44 Å). This interaction is known as an argentophilic interaction [51–57]. Similar to complex 4, there are intermolecular (C H) Ag1 and (C@O) Ag1 interactions (Ag1 H27 = 3.105, Ag1 C27 = 3.244(3) Å and
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Fig. 13. Photoluminescence spectra of 1–5 and Na(sac)H2O.
C27–H27 Ag1 = 92.07°; Ag1 O1 = 2.979(2), Ag1 C1 = 3.402(3) Å and C1 = O1 Ag1 = 99.4(2)°). Moreover, there are C–H p interactions between the C26–H26 unit of the sac ligand and the benzene ring (Cg1) of the mbix ligand [Cg1 = C12, C13, C14, C15, C16, C17, H26 Cg1 = 2.83, C26 Cg1 = 3.541(4) Å and C26 H26 Cg1 = 130(2)°].
characterized. The sac ligand exhibited two coordination modes in the complexes. The Zn(II) and Cd(II) complexes with the bis(imidazole) ligands had polymeric structures while Ag(I) complexes were dinuclear complexes. Photoluminescence spectra showed that complexes 3–5 exhibited blue luminescence which could be beneficial in optical devices.
3.2. Photoluminescent and thermal properties
Acknowledgements
The photoluminescence properties of the d10 complexes and Na(sac)H2O were investigated in the solid state under the same condition at room temperature (Fig. 13). Na(sac)H2O exhibits an emission at 537 nm upon excitation at 379 nm. The emission band of Na(sac)H2O is attributed to p⁄ ? n and p⁄ ? p transitions. As seen in Fig. 13, emission bands are observed at 436 and 537 nm for 1, 529 nm for 2, 438 nm for 3, 446 and 526 nm for 4 and 446 and 520 nm for 5 upon excitation at 379 nm. It is suggested that the photoluminescent properties of complexes 1 and 2 may be assigned to intraligand transitions of the coordinated sac ligand [8]. For 3–5, the emissions shifted blue when compared to Na(sac)H2O. These emissions may be attributed to ligand-to-metal charge-transfer (LMCT) or metal-to-ligand charge-transfer (MLCT) transitions [58]. Thermal analyses were carried out in the temperature range 30–800 °C in a static air atmosphere in order to evaluate the thermal stabilities and thermal behaviors of complexes 1–5 (Figs. S1–S5). Complexes 1 and 4 are stable up to 330 and 284 °C, respectively. For 2 and 3, The first weight losses of 2.66% in the temperature range 33–180 °C and 3.37% in the temperature range 86–157 °C correspond to release of lattice and coordinated water molecules, respectively (calcd. 3.63% for 2; calcd. 4.79% for 3). After the dehydration stages, complexes 2 and 3 are stable up to 220 and 271 °C. There is a slow weight loss for complex 5 up to 270 °C. Above those temperatures, the complexes begin to decompose with endothermic and exothermic peaks. The final residual products are possibly ZnO for 1 (found: 11.72%, calcd. 12.12%), CdO for 2 (found: 13.80%, calcd. 12.98%), CdO for 3 (found: 14.97%, calcd. 14.91%), AgO for 4 (found: 21.43%, calcd. 23.46%) and 5 (found: 15.84%, calcd. 15.16%).
This work was supported by the Scientific Research Fund of Eskisßehir Osmangazi University. Project number: 201319D17.
4. Conclusion Five novel d10 metal complexes containing three isomeric bis(imidazole) ligands and the sac anion were synthesized and
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