- Email: [email protected]
New pyridinium–metal iodide complexes toward nonlinear optical materials
Materials Letters 58 (2004) 2466 – 2471 www.elsevier.com/locate/matlet
New pyridinium–metal iodide complexes toward nonlinear optical materials Zornitza Glavcheva *, Hirohito Umezawa, Shuji Okada, Hachiro Nakanishi Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan Received 10 November 2003; accepted 8 March 2004 Available online 22 April 2004
Abstract New pyridinium – metal iodide complexes were synthesized. The 4-substituted pyridinium iodides X – C5H4N+ – CH3I, where X = methyl, amino, cyano, methoxycarbonyl, carbamoyl, or dimethylamino group, were found to form 2:1 crystalline complexes with ZnI2, except for the carbamoyl derivative, and 1:1 complexes with PbI2. Three SHG active complexes were found from the lead complexes. Among the complexes prepared, the crystal structures of bis(4-cyano-1-methylpyridinium) tetraiodozincate (CNP/ZnI4), bis(4dimethylamino-1-methylpyridinium) tetraiodozincate (DAP/ZnI4), and 1-methyl-4-carbamoylpyridinium triiodoplumbate (CP/PbI3) were investigated. It was found that DAP/ZnI4 and CNP/ZnI4 crystallized in centrosymmetric monoclinic C2/c space group, while the structure of CP/PbI3 was refined in noncentrosymmetric orthorhombic P212121 space group. It was also established that the inorganic parts of both DAP/ ZnI4 and CNP/ZnI4 crystals were composed of [ZnI4]2 anions with tetrahedral structure, and the inorganic moieties of CP/PbI3 consisted of one-dimensional face-sharing lead iodide octahedra. CP/PbI3 was assessed to have approximately one-fourth of the nonlinear optical coefficient (d) of 3-methyl-4-nitropyridine-1-oxide (POM). D 2004 Elsevier B.V. All rights reserved Keywords: Organic – inorganic complexes; Crystal structure; Nonlinear optical materials
1. Introduction The organic – inorganic hybrid complexes present a new promising type of materials for various applications. Their benefits are due to a combination of desirable properties of the inorganic materials such as a wide range of electronic characteristics, mechanical hardness, and thermal stability and, on the other hand, structural variety, large polarizability, and easy processing of the organic molecules [1]. Among them, layered organic– inorganic perovskites [2] still attract a lot of interest because of their application for electroluminescent devices [3], electronic [4] and optoelectronic [5] materials, thin-film field-effect transistors [6], etc. Although the above-mentioned class of materials has been widely studied, the pyridinium – metal halide hybrids are not thoroughly investigated.
* Corresponding author. Fax: +81-22-217-5645. E-mail address: [email protected] (Z. Glavcheva). 0167-577X/$ - see front matter D 2004 Elsevier B.V. All rights reserved doi:10.1016/j.matlet.2004.03.006
Pyridinium cations are good candidates for second-harmonic generation (SHG) materials because they possess large hyperpolarizabilities (b’s) irrespective of the short cutoff wavelength [7a]. Since pyridinium cations are ionic species, they possess an easy tunability into noncentrosymmetric structures by changing counter anions [7b]. When pyridinium cations are combined with metal halide anions, not only the crystal structures, but also the refractive indices of the crystals could be tuned due to exchangeability of metal and halogen species within anions. In our previous studies, pyridinium iodides were combined with cadmium iodide, and two SHG active crystals were obtained, i.e., bis(4-dimethylamino-1methylpyridinium) tetraiodocadmate (DAP/CdI4) [8] and 4carbamoyl-1-methylpyridinium triiodocadmate (CP/CdI3) [9]. In this research, 4-substituted 1-methylpyridinium iodides were combined with other metal iodide (MI2, where M = Zn, Pb), and the compositions and structures of the obtained hybrid complexes were investigated. Crystal structures of three complexes were analyzed, and the feasibility of ZnI2 and PbI2 to form SHG-active complexes with substituted pyridinium iodides is discussed.
Z. Glavcheva et al. / Materials Letters 58 (2004) 2466–2471
2467
2. Experimental
3. Results and discussion
Series of complexes of pyridinium iodides with ZnI2 were synthesized by mixing pyridinium iodide methanol solution and ZnI2 methanol solution in a molar ratio of 2:1, as described in our previous study [8]. The same procedure was applied for obtaining complexes of pyridinium iodides with PbI2 using N,N-dimethylformamide (DMF) as a solvent instead of methanol. A precipitate was immediately produced after mixing the two solutions, and then it was filtrated, washed with ethanol, and dried. The yields of the complexes were about 85 – 90%. The new pyridinium –zinc compounds obtained were purified by recrystallization from acetone– methanol solution, and the pyridinium – lead complexes were recrystallized from DMF solution. Chemical structures of the pyridinium iodide derivatives investigated in this study and the reaction scheme are shown in Fig. 1. Melting points of the powder crystals were measured using a Perkin Elmer Pyris Diamond DSC, and the peak temperatures were taken as melting points. Elementary analyses were obtained from IMRAM, Tohoku University, Japan. The UV –VIS spectra were recorded on a Jasco V570 spectrophotometer. Crushed single crystals with potassium bromide (KBr) were prepared, and their spectra were measured by the diffuse reflection method using a pure KBr sample as a reference. The SHG activity powder test was qualitatively evaluated by irradiating a beam from an Nd:YAP laser at 1079 nm (Elmas L-100). In order to obtain single crystals suitable for X-ray crystallography, the crystal growth was carried out by the slow evaporation method at room temperature for a period of days. X-ray crystallographic studies were performed for crystals 3b, 6b, and 5c using a Mac Science MXC-3 four-circle diffractometer with graphite-monochromatized Mo Ka radiation. The crystal structures were solved by the direct method (SIR92) [10] and refined by the full-matrix least-squares procedure. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were attached to their parent atoms with fixed bond lengths and idealized bond angles. The calculations were performed with the help of CRYSTAN-GM program [11].
All new complexes except the combination of carbamoyl derivative 5 (Fig. 1) with ZnI2 were successfully obtained in high yields. In the case of Cd complexes, 2:1 complexes between pyridinium iodide and CdI2 were generally obtained, and a 1:1 complex was exceptionally produced for 5 to give 5a. Since carbamoyl cations form intermolecular hydrogen bonding between carbamoyl groups in crystals [9], this restriction may cause to show different feature. Table 1 summarizes the melting points, the results of the elemental analysis together with calculated composition ratios of the assessed structures, and the absorption maximum wavelength (kmax) of 1b – 4b, 6b, and 1c– 6c. Zinc complexes except 4b have relatively high melting points above 180 jC, whose maximum melting point is 228 jC. Lead complexes have much higher melting point (257 – 309 jC) than zinc derivatives, which make them suitable for further applications because of their thermal stability. From the elementary analysis of the complexes, the composition ratios of pyridinium iodide to metal iodide were confirmed to be 2:1 for Zn complexes and 1:1 for Pb complexes, respectively. It is interesting to notice that only 3c contains DMF. The pyridinium – zinc iodide complexes 1b, 2b, and 6b are colorless, while 3b, 4b, and all lead complexes 1c– 6c are yellow. The kmax of the zinc complexes vary in the region of 277 – 376 nm depending on cationic chromophores, indicating that these bands originated from the cationic chromophores. On the other hand, the UV –VIS spectra of the lead complexes show the kmax at 370 – 388 nm. These bands are generally due to lead iodide moiety because these wavelengths are all similar and longer than the kmax of the cationic species included. SHG was observed in the crystals of 3c, 5c, and 6c with similar intensities. They are all Pb complexes, and no SHG active Zn complex was obtained. Among the Cd complexes 1a –6a, 5a (1:1 complex) and 6a (2:1 complex) showed SHG activity [8,9]. Thus, it is likely that 1:1 complexes could have more probability to generate noncentrosymmetric structures. The crystallographic data of 3b (CNP/ZnI4), 6b (DAP/ ZnI4), and 5c (CP/PbI3) are shown in Table 2. The crystal
Fig. 1. Reaction scheme between 4-substituted 1-methyl-1pyridinium iodides and metal iodide. The cadmium complexes 1a – 6a have been prepared previously [8,9].
2468
Z. Glavcheva et al. / Materials Letters 58 (2004) 2466–2471
Table 1 The melting points, the results of the elemental analysis, and absorption maximum wavelengths (kmax) of the pyridinium complexes with zinc iodide and lead iodide Complex
Melting point (jC)
Found C; H; N (%) [calculated C; H; N (%)]a
kmax
1b 2b 3b 4b 6b 1c 2c 3c 4c 5c 6c
212 185 228 128 189 309 307 233 304 257 297
21.20; 2.56; 3.52 (21.30; 2.55; 3.55) 18.04; 2.29; 7.10 (18.21; 2.29; 7.08) 20.68; 1.94; 6.72 (20.72; 1.74; 6.90) 21.79; 2.29; 3.25 (21.90; 2.30; 3.21) 22.54; 2.92; 6.62 (22.68; 3.09; 6.61) 11.87; 1.64; 1.97 (12.08; 1.44; 2.01) 10.33; 1.53; 4.08 (10.34; 1.30; 4.02) 15.26; 1.82; 5.39 (15.39; 1.81; 5.41) 12.39; 1.44; 1.81 (12.98; 1.36; 1.89) 11.59; 1.38; 3.61 (11.60; 1.25; 3.86) 13.19; 1.81; 3.85 (13.24; 1.65; 3.82)
301 277 376 359 307 381 370 384 378 388 376
a Calculated ratios between pyridinium iodide and metal iodide are 2:1 for Zn complexes and 1:1 for Pb complexes, respectively, in general. Only 3c was found to contain DMF, and its calculated ratio among pyridinium iodide, metal iodide, and DMF is 1:1:1.
structures of both Zn complexes belong to the centrosymmetric monoclinic space group C2/c. The asymmetric units of CNP/ZnI4 and DAP/ZnI4 crystals consist of one pyridinium cation and a half of zinc iodide anion as shown in Fig. 2(a) and (b). Although the empirical formulae of CNP/ZnI4 and DAP/ZnI4 are the same as those of the basic layered perovskites structure with metal halide octahedra [1,2], the inorganic parts of 3b and 6b are different as shown in Figs. 3 and 4. Zinc iodide anion can be described as [ZnI4]2 and has a tetrahedral structure with a Zn atom at the center and four I atoms at each corner. Similar anion structures have been found in the corresponding Cd hybrids [8], some pyridinium –copper halide complexes [12], other ammonium Zn complexes [13], etc. The inorganic parts in CNP/ ZnI4 and DAP/ZnI4 hybrids have a topologically identical layered arrangement, in which the layers are parallel to the (001) plane. In addition, the anions possess quite similar geometric parameters with very small distortions from the regular tetrahedron: IUZn distances are in the range of Table 2 Crystallographic data of CNP/ZnI4, DAP/ZnI4, and CP/PbI3 Abbreviation Formula Formula weight Crystal system Space group ˚) a (A ˚) b (A ˚) c (A b (j) ˚ 3) V (A Z Dcalc. (mg m 3) l (mm 1) No. of observed reflections R Rw
CNP/ZnI4 C14H14N4I4Zn 811.30 monoclinic C2/c 20.80(2) 7.763(9) 14.69(1) 113.60(6) 2171.4(3) 4 2.481 6.792 2348; I >2r(I)
DAP/ZnI4 C16H26N4I4Zn 847.40 monoclinic C2/c 15.35(1) 11.127(7) 15.72(1) 94.49(6) 2676.4(3) 4 2.103 5.514 2501; I >2r(I)
CP/PbI3 C8H9N2OPbI3 725.07 orthorhombic P212121 9.630(8) 19.38(1) 7.955(5)
0.059 0.083
0.055 0.077
0.058 0.083
1484.4(2) 4 3.244 17.608 1424; I >3r(I)
Fig. 2. The asymmetric unit of CNP/ZnI4 (a) and DAP/ZnI4 (b) in their crystal structures. Displacement ellipsoids for the non-H atoms are shown at 50% probability level.
˚ , and IUZnUI bond angles are in the range of 2.61– 2.63 A 107 – 112j. However, the orientation of the pyridinium moieties is different for both crystals. Namely, comparing the angle h between molecular long axis of pyridinium cations and crystallographic b-axis, CNP/ZnI4 has the h value larger than DAP/ZnI4, which results in a shorter b parameter of the unit cell for CNP/ZnI4. The bond lengths and angles of the organic parts of CNP/ZnI4 and DAP/ZnI4 are consistent with those of the pyridinium cadmium iodide complexes [8]. The cations are nearly planar with distances and angles in the normal ranges. This indicates that the normal lone pair of the amino nitrogen atom is conjugated with the pyridinium k-electron system. It is well known that the lead-halide-based layered perovskite often consists of corner-sharing PbX6 octahedra [14,15]. Kawahara et al. [16] reported the crystal structure of 4,4V-bipyridinium dibromide combined with PbBr2, in which the anions build one-dimensional chains of sidesharing PbBr6 octahedra. In the case of CP/PbI3, the inorganic portion forms one-dimensional chains of facesharing PbI6 octahedra (Fig. 5). Each lead atom at the center
Z. Glavcheva et al. / Materials Letters 58 (2004) 2466–2471
2469
Fig. 3. Crystal structure of CNP/ZnI4 viewed along the [100] direction (a) and along the [010] direction (b). The [ZnI4]2 anions are represented by tetrahedra. Hydrogen atoms are omitted.
of the octahedra is connected to six iodine atoms at the corners. The asymmetric unit consists of a [PbI3] unit (a part of the face-shared octahedral chain) and one 1-methyl4-carbamoylpyridinium cation. The Pb –I distances range ˚ , and IUPbUI bond angles vary from from 3.177 to 3.304 A 82.3j to 97.8j, suggesting a slight distortion from regular octahedra. One-dimensional chains of face-sharing PbI6 octahedra aligned along the c-axis as can be seen in Fig. 6. The CP/PbI3 crystal belongs to the noncentrosymmetric space group P212121, and there have been several reports on noncentrosymmetric crystal structures with the similar facesharing octahedral [PbX3]n chains, e.g., piperidinium triiodoplumbate(II) [17a], morphorinium trihaloplumnates(II) [17b], and (DAMS)PbI32DMSO [18], where DAMS is trans-4-[(4-dimethylamino)styryl]-1-methylpyridinium and DMSO is dimethylsulfoxide. Meanwhile, tetramethylammonium triiodoplumbate(II) [19a], triphenylmethylphosphonium triiodoplumbate(II) [19b], and pyridinium triiodoplumbate(II) [19c] were reported to have centrosym-
metric crystal structures with the face-sharing octahedral [PbX3]n chains. Accordingly, the probability to become noncentrosymmetric crystal structures seems to be fairly high when the face-sharing octahedral [PbX3]n chains are introduced. For the 1:1 complexes from PbI2, several types of crystal structures have been reported as follows. The crystal of (CH3NH2)PbI3 has a cubic perovskite structure with PbI6 octahedra [20]. On the other hand, isolated anions such as [PbI4]2 and [Pb2I6]2 have also been found [21]. There are other types of one-dimensional chain structures composed of base-side-sharing square pyramids [21,22] or double-chain side-sharing octahedra [23]. Thus, it is interesting to solve the crystal structures of other Pb complexes, although their single crystals with good quality could not been grown so far. The bond lengths and angles of the organic portion of CP/PbI3 were similar to those of the corresponding cadmium iodide complexes [9]. The carbamoyl group of a pyridinium cation forms intermolecular hydrogen bond with the two adjacent cations, and there are
Fig. 4. Crystal structure of DAP/ZnI4 viewed along the [100] direction (a) and along the [010] direction (b). The [ZnI4]2 anions are represented by tetrahedra. Hydrogen atoms are omitted.
2470
Z. Glavcheva et al. / Materials Letters 58 (2004) 2466–2471
method. The major four b components bxxx , bxyy , byyy , and byxx were obtained to be 3.44 10 30, 1.43 10 30, 1.33 10 30, and 0.69 10 30 esu, respectively, when the x-axis was taken to the molecular long-axis direction and the y-axis was perpendicular to the x-axis in the aromatic plane. By using these values, the d14 value of CP/PbI3 at 1064 nm was calculated to be 1.7 pm/V. Using the same procedure referring the crystallographic data of POM [27], the d14 value of POM was obtained to be 7.5 pm/ V. Small d value of CP/PbI3 is originated from the following reasons: lower density of NLO chromophores mainly due to the [PbI3]n portion (about 44% of the NLO chromophore density of POM) and smaller b and orientational factor (about a half of those of POM).
Fig. 5. Cation and a part of face-shared octahedral chain in the CP/PbI3 crystal with displacement ellipsoids for the non-H atoms at 50% probability level.
one-dimensional arrays along the a-axis [Fig. 6(b)]. The ::: NUH O hydrogen bond can be described as weak because ::: ˚ ) between the adjacent cations is the N O distance (2.95 A slightly less than the sum of the van der Waals radii of nitrogen and oxygen [24]. Since CP/PbI 3 crystallizes in noncentrosymmetric P212121 space group (class 222-D2 symmetry) as mentioned above, there are three nonvanishing components of the second-harmonic coefficient, i.e., off-diagonal d14, d25, and d36. These d values (dXYZ) can be estimated using the oriented gas model [25]: dXYZ ¼
NfX2x fYx fZx X X cosðX ; xðsÞÞcosðY ; yðsÞÞ Z i;j;k s cosðZ; zðsÞÞbijk ðsÞ
where N is the number of chromophores per unit volume, f terms are Lorentz’s local field factors, Z is the number of chromophores per unit cell, (X,x(s)) is the angle between the crystallographic X-axis and the molecular x-axis, and s indicates the individual chromophores in the unit cell. Since the refractive indices of CP/PbI3 crystals were difficult to be evaluated, we simply assumed that the f values were the same as those of 3-methyl-4-nitropyridine-1-oxide (POM) [26], which has no strong absorption in the visible region and crystallizes into the same space group as CP/PbI3. This assumption causes underestimated d values because CP/PbI3 contains heavy elements such as lead and iodine, which increase the refractive index, and it was not taken into account using the refractive indices of POM. The b of 1methyl-4-carbamoylpyridinium cation were calculated for its molecular structure in the crystal by the MOPAC PM3
Fig. 6. Crystal structure of CP/PbI3 viewed along the [100] direction (a) and along the [001] direction (b). Hydrogen bonds are illustrated with dotted lines. The inorganic parts are represented by chains of face-sharing PbI6 octahedra.
Z. Glavcheva et al. / Materials Letters 58 (2004) 2466–2471
4. Conclusion New complexes of 4-substituted 1-methylpyridinium iodide with zinc or lead iodide were synthesized. Among the obtained compounds, the composition ratios of pyridinium iodide to metal iodide were confirmed to be 2:1 for Zn complexes and 1:1 for Pb complexes, respectively. Three complexes were found to be SHG active among six lead complexes synthesized, although no SHG active complex was obtained within five zinc complexes prepared. The crystal structures of CNP/ZnI4, DAP/ZnI4, and SHG active CP/PbI3 were determined, and it was found that the inorganic part in both pyridinium – zinc complexes possesses [ZnI4]2 with the isolated tetrahedral structure, and the anions in CP/ PbI3 form [PbI3]n with one-dimensional sequence of facesharing octahedra. For CP/PbI3, the off-diagonal d component was estimated to be about 23% of that of POM. At this stage, we found that noncentrosymmetric crystal structures could be attained even for pyridinium –metal halide complexes when the proper metal halide was selected. Combination with high-b chromophores and optimization of the chromophore alignment are interesting subjects for further investigation.
[8] [9] [10]
[11] [12]
[13]
[14] [15] [16] [17]
References [1] D.B. Mitzi, K. Chondroudis, C.R. Kagan, Org. Electron. 45 (2001) 29. [2] D.B. Mitzi, Progress in Inorganic Chemistry, vol. 48, Wiley, New York, 1999, p. 1. [3] M. Era, S. Morimoto, T. Tsutsui, S. Saito, Appl. Phys. Lett. 65 (1994) 676. [4] C.R. Kagan, D.B. Mitzi, C.D. Dimitrakopoulos, Science 286 (1999) 945. [5] T. Kataoka, T. Kondo, R. Ito, S. Sasaki, K. Uchida, N. Miura, Phys. B 201 (1994) 423. [6] G.C. Papavassiliou, G.A. Mousdisa, I.B. Koutselas, Synth. Met. 121 (2001) 1339. [7] (a) Anwar, X.-M. Duan, K. Komatsu, S. Okada, H. Matsuda, H. Oikawa, H. Nakanishi, Chem. Lett. (1997) 247; (b) Anwar, K. Komatsu, S. Okada, H. Oikawa, H. Matsuda, H. Nakanishi, Proc. SPIE 3796 (1999) 219; (c) Anwar, X.-M. Duan, K. Komatsu, S. Okada, H. Oikawa, H. Matsuda, H. Nakanishi, Nonlinear Opt. 22 (1999) 251; (d) Anwar, S. Okada, H. Oikawa, H. Nakanishi, Chem. Mater. 12 (2000) 1162;
[18] [19]
[20] [21] [22] [23] [24] [25] [26] [27]
2471
(e) A. Anwar, H. Kosuge, S. Okada, H. Oikawa, H. Nakanishi, Jpn. J. Appl. Phys. 40 (2001) 4213. K. Kosuge, S. Okada, H. Oikawa, H. Nakanishi, Supramol. Chem. 13 (2001) 233. K. Kosuge, S. Okada, H. Oikawa, H. Nakanishi, Mol. Cryst. Liq. Cryst. 377 (2002) 265. SIR92, A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M.C. Burla, G. Polidori, M. Camalli, J. Appl. Crystallogr. 27 (1994) 435. Crystan-GM, MAC Science, Yokohama, 1994. (a) S. Haddad, R.D. Willett, Inorg. Chem. 40 (2001) 2457; (b) S. Haddad, R.D. Willett, J. Chem. Crystallogr. 31 (2001) 37; (c) G. Pon, R. Willett, A. Prince, T. Robinson, M. Turnbull, Inorg. Chim. Acta 255 (1997) 325. (a) K. Hayase, T. Asahi, K. Gesi, Acta Crystallogr. C46 (1990) 218; (b) M.L. Werk, G. Chapuis, F.J. Zu´n˜iga, Acta Crystallogr. B46 (1990) 187; (c) W.T.A. Harrison, R.A. Howie, J. Skakle, J.L. Wardell, Acta Crystallogr. C56 (2000) e124. J. Calabrese, N.L. Jones, R.L. Harlow, N. Herron, D.L. Thorn, Y. Wang, J. Am. Chem. Soc. 113 (1991) 2328. M. Braun, W. Tuffentsammer, H. Wachtel, H.C. Wolf, Chem. Phys. Lett. 303 (1999) 157. M. Kawahara, K. Teshima, M. Rikukawa, K. Sanui, Synth. Met. 121 (2001) 1331. (a) G.V. Gridunova, E.A. Ziger, V.M. Koshkin, S.V. Lindeman, Yu.T. Struchkov, V.E. Shklover, Dokl. Akad. Nauk. SSSR 278 (1984) 656; (b) M. Geselle, H. Fuess, Z. Kristallogr., New Cryst. Struct. 212 (1997) 235; (c) A.B. Corradi, S. Bruni, F. Cariati, A.M. Ferrari, A. Sandccani, F. Srolini, P. Sgarabotto, Inorg. Chim. Acta 254 (1997) 137. M. Guloy, Z. Tang, P.B. Miranda, V.I. Srdanov, Adv. Mater. 13 (2001) 833. (a) J.G. Contreras, G.V. Seguel, B. Ungerer, W.F. Maier, F.J. Hollander, J. Mol. Struct. 102 (1983) 295; (b) M. El Essawi, R. Wartchow, H.J. Berthold, Z. Kristallogr. 212 (1997) 163; (c) M. Geselle, H. Fuess, Z. Kristallogr., New Cryst. Struct. 212 (1997) 235. D. Weber, Z. Naturforsch. 33b (1978) 1443. H. Krautcheid, F. Vielsack, Z. Anorg. Allg. Chem. 625 (1999) 562. M. Geselle, H. Fuess, Z. Kristallogr., New Cryst. Struct. 212 (1997) 237. M. Geselle, H. Fuess, Z. Kristallogr., New Cryst. Struct. 212 (1997) 243. 243. J. Emsley, Chem. Soc. Rev. 9 (1980) 91. J. Zyss, J.L. Ouder, Phys. Rev. A 26 (1982) 2028. J. Zyss, D.S. Chemla, J.F. Nicoud, J. Chem. Phys. 74 (1981) 4800. M. Shiro, M. Yamakawa, T. Kubota, Acta Crystallogr. B33 (1977) 1549.
New pyridinium–metal iodide complexes toward nonlinear optical materials Zornitza Glavcheva *, Hirohito Umezawa, Shuji Okada, Hachiro Nakanishi Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan Received 10 November 2003; accepted 8 March 2004 Available online 22 April 2004
Abstract New pyridinium – metal iodide complexes were synthesized. The 4-substituted pyridinium iodides X – C5H4N+ – CH3I, where X = methyl, amino, cyano, methoxycarbonyl, carbamoyl, or dimethylamino group, were found to form 2:1 crystalline complexes with ZnI2, except for the carbamoyl derivative, and 1:1 complexes with PbI2. Three SHG active complexes were found from the lead complexes. Among the complexes prepared, the crystal structures of bis(4-cyano-1-methylpyridinium) tetraiodozincate (CNP/ZnI4), bis(4dimethylamino-1-methylpyridinium) tetraiodozincate (DAP/ZnI4), and 1-methyl-4-carbamoylpyridinium triiodoplumbate (CP/PbI3) were investigated. It was found that DAP/ZnI4 and CNP/ZnI4 crystallized in centrosymmetric monoclinic C2/c space group, while the structure of CP/PbI3 was refined in noncentrosymmetric orthorhombic P212121 space group. It was also established that the inorganic parts of both DAP/ ZnI4 and CNP/ZnI4 crystals were composed of [ZnI4]2 anions with tetrahedral structure, and the inorganic moieties of CP/PbI3 consisted of one-dimensional face-sharing lead iodide octahedra. CP/PbI3 was assessed to have approximately one-fourth of the nonlinear optical coefficient (d) of 3-methyl-4-nitropyridine-1-oxide (POM). D 2004 Elsevier B.V. All rights reserved Keywords: Organic – inorganic complexes; Crystal structure; Nonlinear optical materials
1. Introduction The organic – inorganic hybrid complexes present a new promising type of materials for various applications. Their benefits are due to a combination of desirable properties of the inorganic materials such as a wide range of electronic characteristics, mechanical hardness, and thermal stability and, on the other hand, structural variety, large polarizability, and easy processing of the organic molecules [1]. Among them, layered organic– inorganic perovskites [2] still attract a lot of interest because of their application for electroluminescent devices [3], electronic [4] and optoelectronic [5] materials, thin-film field-effect transistors [6], etc. Although the above-mentioned class of materials has been widely studied, the pyridinium – metal halide hybrids are not thoroughly investigated.
* Corresponding author. Fax: +81-22-217-5645. E-mail address: [email protected] (Z. Glavcheva). 0167-577X/$ - see front matter D 2004 Elsevier B.V. All rights reserved doi:10.1016/j.matlet.2004.03.006
Pyridinium cations are good candidates for second-harmonic generation (SHG) materials because they possess large hyperpolarizabilities (b’s) irrespective of the short cutoff wavelength [7a]. Since pyridinium cations are ionic species, they possess an easy tunability into noncentrosymmetric structures by changing counter anions [7b]. When pyridinium cations are combined with metal halide anions, not only the crystal structures, but also the refractive indices of the crystals could be tuned due to exchangeability of metal and halogen species within anions. In our previous studies, pyridinium iodides were combined with cadmium iodide, and two SHG active crystals were obtained, i.e., bis(4-dimethylamino-1methylpyridinium) tetraiodocadmate (DAP/CdI4) [8] and 4carbamoyl-1-methylpyridinium triiodocadmate (CP/CdI3) [9]. In this research, 4-substituted 1-methylpyridinium iodides were combined with other metal iodide (MI2, where M = Zn, Pb), and the compositions and structures of the obtained hybrid complexes were investigated. Crystal structures of three complexes were analyzed, and the feasibility of ZnI2 and PbI2 to form SHG-active complexes with substituted pyridinium iodides is discussed.
Z. Glavcheva et al. / Materials Letters 58 (2004) 2466–2471
2467
2. Experimental
3. Results and discussion
Series of complexes of pyridinium iodides with ZnI2 were synthesized by mixing pyridinium iodide methanol solution and ZnI2 methanol solution in a molar ratio of 2:1, as described in our previous study [8]. The same procedure was applied for obtaining complexes of pyridinium iodides with PbI2 using N,N-dimethylformamide (DMF) as a solvent instead of methanol. A precipitate was immediately produced after mixing the two solutions, and then it was filtrated, washed with ethanol, and dried. The yields of the complexes were about 85 – 90%. The new pyridinium –zinc compounds obtained were purified by recrystallization from acetone– methanol solution, and the pyridinium – lead complexes were recrystallized from DMF solution. Chemical structures of the pyridinium iodide derivatives investigated in this study and the reaction scheme are shown in Fig. 1. Melting points of the powder crystals were measured using a Perkin Elmer Pyris Diamond DSC, and the peak temperatures were taken as melting points. Elementary analyses were obtained from IMRAM, Tohoku University, Japan. The UV –VIS spectra were recorded on a Jasco V570 spectrophotometer. Crushed single crystals with potassium bromide (KBr) were prepared, and their spectra were measured by the diffuse reflection method using a pure KBr sample as a reference. The SHG activity powder test was qualitatively evaluated by irradiating a beam from an Nd:YAP laser at 1079 nm (Elmas L-100). In order to obtain single crystals suitable for X-ray crystallography, the crystal growth was carried out by the slow evaporation method at room temperature for a period of days. X-ray crystallographic studies were performed for crystals 3b, 6b, and 5c using a Mac Science MXC-3 four-circle diffractometer with graphite-monochromatized Mo Ka radiation. The crystal structures were solved by the direct method (SIR92) [10] and refined by the full-matrix least-squares procedure. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were attached to their parent atoms with fixed bond lengths and idealized bond angles. The calculations were performed with the help of CRYSTAN-GM program [11].
All new complexes except the combination of carbamoyl derivative 5 (Fig. 1) with ZnI2 were successfully obtained in high yields. In the case of Cd complexes, 2:1 complexes between pyridinium iodide and CdI2 were generally obtained, and a 1:1 complex was exceptionally produced for 5 to give 5a. Since carbamoyl cations form intermolecular hydrogen bonding between carbamoyl groups in crystals [9], this restriction may cause to show different feature. Table 1 summarizes the melting points, the results of the elemental analysis together with calculated composition ratios of the assessed structures, and the absorption maximum wavelength (kmax) of 1b – 4b, 6b, and 1c– 6c. Zinc complexes except 4b have relatively high melting points above 180 jC, whose maximum melting point is 228 jC. Lead complexes have much higher melting point (257 – 309 jC) than zinc derivatives, which make them suitable for further applications because of their thermal stability. From the elementary analysis of the complexes, the composition ratios of pyridinium iodide to metal iodide were confirmed to be 2:1 for Zn complexes and 1:1 for Pb complexes, respectively. It is interesting to notice that only 3c contains DMF. The pyridinium – zinc iodide complexes 1b, 2b, and 6b are colorless, while 3b, 4b, and all lead complexes 1c– 6c are yellow. The kmax of the zinc complexes vary in the region of 277 – 376 nm depending on cationic chromophores, indicating that these bands originated from the cationic chromophores. On the other hand, the UV –VIS spectra of the lead complexes show the kmax at 370 – 388 nm. These bands are generally due to lead iodide moiety because these wavelengths are all similar and longer than the kmax of the cationic species included. SHG was observed in the crystals of 3c, 5c, and 6c with similar intensities. They are all Pb complexes, and no SHG active Zn complex was obtained. Among the Cd complexes 1a –6a, 5a (1:1 complex) and 6a (2:1 complex) showed SHG activity [8,9]. Thus, it is likely that 1:1 complexes could have more probability to generate noncentrosymmetric structures. The crystallographic data of 3b (CNP/ZnI4), 6b (DAP/ ZnI4), and 5c (CP/PbI3) are shown in Table 2. The crystal
Fig. 1. Reaction scheme between 4-substituted 1-methyl-1pyridinium iodides and metal iodide. The cadmium complexes 1a – 6a have been prepared previously [8,9].
2468
Z. Glavcheva et al. / Materials Letters 58 (2004) 2466–2471
Table 1 The melting points, the results of the elemental analysis, and absorption maximum wavelengths (kmax) of the pyridinium complexes with zinc iodide and lead iodide Complex
Melting point (jC)
Found C; H; N (%) [calculated C; H; N (%)]a
kmax
1b 2b 3b 4b 6b 1c 2c 3c 4c 5c 6c
212 185 228 128 189 309 307 233 304 257 297
21.20; 2.56; 3.52 (21.30; 2.55; 3.55) 18.04; 2.29; 7.10 (18.21; 2.29; 7.08) 20.68; 1.94; 6.72 (20.72; 1.74; 6.90) 21.79; 2.29; 3.25 (21.90; 2.30; 3.21) 22.54; 2.92; 6.62 (22.68; 3.09; 6.61) 11.87; 1.64; 1.97 (12.08; 1.44; 2.01) 10.33; 1.53; 4.08 (10.34; 1.30; 4.02) 15.26; 1.82; 5.39 (15.39; 1.81; 5.41) 12.39; 1.44; 1.81 (12.98; 1.36; 1.89) 11.59; 1.38; 3.61 (11.60; 1.25; 3.86) 13.19; 1.81; 3.85 (13.24; 1.65; 3.82)
301 277 376 359 307 381 370 384 378 388 376
a Calculated ratios between pyridinium iodide and metal iodide are 2:1 for Zn complexes and 1:1 for Pb complexes, respectively, in general. Only 3c was found to contain DMF, and its calculated ratio among pyridinium iodide, metal iodide, and DMF is 1:1:1.
structures of both Zn complexes belong to the centrosymmetric monoclinic space group C2/c. The asymmetric units of CNP/ZnI4 and DAP/ZnI4 crystals consist of one pyridinium cation and a half of zinc iodide anion as shown in Fig. 2(a) and (b). Although the empirical formulae of CNP/ZnI4 and DAP/ZnI4 are the same as those of the basic layered perovskites structure with metal halide octahedra [1,2], the inorganic parts of 3b and 6b are different as shown in Figs. 3 and 4. Zinc iodide anion can be described as [ZnI4]2 and has a tetrahedral structure with a Zn atom at the center and four I atoms at each corner. Similar anion structures have been found in the corresponding Cd hybrids [8], some pyridinium –copper halide complexes [12], other ammonium Zn complexes [13], etc. The inorganic parts in CNP/ ZnI4 and DAP/ZnI4 hybrids have a topologically identical layered arrangement, in which the layers are parallel to the (001) plane. In addition, the anions possess quite similar geometric parameters with very small distortions from the regular tetrahedron: IUZn distances are in the range of Table 2 Crystallographic data of CNP/ZnI4, DAP/ZnI4, and CP/PbI3 Abbreviation Formula Formula weight Crystal system Space group ˚) a (A ˚) b (A ˚) c (A b (j) ˚ 3) V (A Z Dcalc. (mg m 3) l (mm 1) No. of observed reflections R Rw
CNP/ZnI4 C14H14N4I4Zn 811.30 monoclinic C2/c 20.80(2) 7.763(9) 14.69(1) 113.60(6) 2171.4(3) 4 2.481 6.792 2348; I >2r(I)
DAP/ZnI4 C16H26N4I4Zn 847.40 monoclinic C2/c 15.35(1) 11.127(7) 15.72(1) 94.49(6) 2676.4(3) 4 2.103 5.514 2501; I >2r(I)
CP/PbI3 C8H9N2OPbI3 725.07 orthorhombic P212121 9.630(8) 19.38(1) 7.955(5)
0.059 0.083
0.055 0.077
0.058 0.083
1484.4(2) 4 3.244 17.608 1424; I >3r(I)
Fig. 2. The asymmetric unit of CNP/ZnI4 (a) and DAP/ZnI4 (b) in their crystal structures. Displacement ellipsoids for the non-H atoms are shown at 50% probability level.
˚ , and IUZnUI bond angles are in the range of 2.61– 2.63 A 107 – 112j. However, the orientation of the pyridinium moieties is different for both crystals. Namely, comparing the angle h between molecular long axis of pyridinium cations and crystallographic b-axis, CNP/ZnI4 has the h value larger than DAP/ZnI4, which results in a shorter b parameter of the unit cell for CNP/ZnI4. The bond lengths and angles of the organic parts of CNP/ZnI4 and DAP/ZnI4 are consistent with those of the pyridinium cadmium iodide complexes [8]. The cations are nearly planar with distances and angles in the normal ranges. This indicates that the normal lone pair of the amino nitrogen atom is conjugated with the pyridinium k-electron system. It is well known that the lead-halide-based layered perovskite often consists of corner-sharing PbX6 octahedra [14,15]. Kawahara et al. [16] reported the crystal structure of 4,4V-bipyridinium dibromide combined with PbBr2, in which the anions build one-dimensional chains of sidesharing PbBr6 octahedra. In the case of CP/PbI3, the inorganic portion forms one-dimensional chains of facesharing PbI6 octahedra (Fig. 5). Each lead atom at the center
Z. Glavcheva et al. / Materials Letters 58 (2004) 2466–2471
2469
Fig. 3. Crystal structure of CNP/ZnI4 viewed along the [100] direction (a) and along the [010] direction (b). The [ZnI4]2 anions are represented by tetrahedra. Hydrogen atoms are omitted.
of the octahedra is connected to six iodine atoms at the corners. The asymmetric unit consists of a [PbI3] unit (a part of the face-shared octahedral chain) and one 1-methyl4-carbamoylpyridinium cation. The Pb –I distances range ˚ , and IUPbUI bond angles vary from from 3.177 to 3.304 A 82.3j to 97.8j, suggesting a slight distortion from regular octahedra. One-dimensional chains of face-sharing PbI6 octahedra aligned along the c-axis as can be seen in Fig. 6. The CP/PbI3 crystal belongs to the noncentrosymmetric space group P212121, and there have been several reports on noncentrosymmetric crystal structures with the similar facesharing octahedral [PbX3]n chains, e.g., piperidinium triiodoplumbate(II) [17a], morphorinium trihaloplumnates(II) [17b], and (DAMS)PbI32DMSO [18], where DAMS is trans-4-[(4-dimethylamino)styryl]-1-methylpyridinium and DMSO is dimethylsulfoxide. Meanwhile, tetramethylammonium triiodoplumbate(II) [19a], triphenylmethylphosphonium triiodoplumbate(II) [19b], and pyridinium triiodoplumbate(II) [19c] were reported to have centrosym-
metric crystal structures with the face-sharing octahedral [PbX3]n chains. Accordingly, the probability to become noncentrosymmetric crystal structures seems to be fairly high when the face-sharing octahedral [PbX3]n chains are introduced. For the 1:1 complexes from PbI2, several types of crystal structures have been reported as follows. The crystal of (CH3NH2)PbI3 has a cubic perovskite structure with PbI6 octahedra [20]. On the other hand, isolated anions such as [PbI4]2 and [Pb2I6]2 have also been found [21]. There are other types of one-dimensional chain structures composed of base-side-sharing square pyramids [21,22] or double-chain side-sharing octahedra [23]. Thus, it is interesting to solve the crystal structures of other Pb complexes, although their single crystals with good quality could not been grown so far. The bond lengths and angles of the organic portion of CP/PbI3 were similar to those of the corresponding cadmium iodide complexes [9]. The carbamoyl group of a pyridinium cation forms intermolecular hydrogen bond with the two adjacent cations, and there are
Fig. 4. Crystal structure of DAP/ZnI4 viewed along the [100] direction (a) and along the [010] direction (b). The [ZnI4]2 anions are represented by tetrahedra. Hydrogen atoms are omitted.
2470
Z. Glavcheva et al. / Materials Letters 58 (2004) 2466–2471
method. The major four b components bxxx , bxyy , byyy , and byxx were obtained to be 3.44 10 30, 1.43 10 30, 1.33 10 30, and 0.69 10 30 esu, respectively, when the x-axis was taken to the molecular long-axis direction and the y-axis was perpendicular to the x-axis in the aromatic plane. By using these values, the d14 value of CP/PbI3 at 1064 nm was calculated to be 1.7 pm/V. Using the same procedure referring the crystallographic data of POM [27], the d14 value of POM was obtained to be 7.5 pm/ V. Small d value of CP/PbI3 is originated from the following reasons: lower density of NLO chromophores mainly due to the [PbI3]n portion (about 44% of the NLO chromophore density of POM) and smaller b and orientational factor (about a half of those of POM).
Fig. 5. Cation and a part of face-shared octahedral chain in the CP/PbI3 crystal with displacement ellipsoids for the non-H atoms at 50% probability level.
one-dimensional arrays along the a-axis [Fig. 6(b)]. The ::: NUH O hydrogen bond can be described as weak because ::: ˚ ) between the adjacent cations is the N O distance (2.95 A slightly less than the sum of the van der Waals radii of nitrogen and oxygen [24]. Since CP/PbI 3 crystallizes in noncentrosymmetric P212121 space group (class 222-D2 symmetry) as mentioned above, there are three nonvanishing components of the second-harmonic coefficient, i.e., off-diagonal d14, d25, and d36. These d values (dXYZ) can be estimated using the oriented gas model [25]: dXYZ ¼
NfX2x fYx fZx X X cosðX ; xðsÞÞcosðY ; yðsÞÞ Z i;j;k s cosðZ; zðsÞÞbijk ðsÞ
where N is the number of chromophores per unit volume, f terms are Lorentz’s local field factors, Z is the number of chromophores per unit cell, (X,x(s)) is the angle between the crystallographic X-axis and the molecular x-axis, and s indicates the individual chromophores in the unit cell. Since the refractive indices of CP/PbI3 crystals were difficult to be evaluated, we simply assumed that the f values were the same as those of 3-methyl-4-nitropyridine-1-oxide (POM) [26], which has no strong absorption in the visible region and crystallizes into the same space group as CP/PbI3. This assumption causes underestimated d values because CP/PbI3 contains heavy elements such as lead and iodine, which increase the refractive index, and it was not taken into account using the refractive indices of POM. The b of 1methyl-4-carbamoylpyridinium cation were calculated for its molecular structure in the crystal by the MOPAC PM3
Fig. 6. Crystal structure of CP/PbI3 viewed along the [100] direction (a) and along the [001] direction (b). Hydrogen bonds are illustrated with dotted lines. The inorganic parts are represented by chains of face-sharing PbI6 octahedra.
Z. Glavcheva et al. / Materials Letters 58 (2004) 2466–2471
4. Conclusion New complexes of 4-substituted 1-methylpyridinium iodide with zinc or lead iodide were synthesized. Among the obtained compounds, the composition ratios of pyridinium iodide to metal iodide were confirmed to be 2:1 for Zn complexes and 1:1 for Pb complexes, respectively. Three complexes were found to be SHG active among six lead complexes synthesized, although no SHG active complex was obtained within five zinc complexes prepared. The crystal structures of CNP/ZnI4, DAP/ZnI4, and SHG active CP/PbI3 were determined, and it was found that the inorganic part in both pyridinium – zinc complexes possesses [ZnI4]2 with the isolated tetrahedral structure, and the anions in CP/ PbI3 form [PbI3]n with one-dimensional sequence of facesharing octahedra. For CP/PbI3, the off-diagonal d component was estimated to be about 23% of that of POM. At this stage, we found that noncentrosymmetric crystal structures could be attained even for pyridinium –metal halide complexes when the proper metal halide was selected. Combination with high-b chromophores and optimization of the chromophore alignment are interesting subjects for further investigation.
[8] [9] [10]
[11] [12]
[13]
[14] [15] [16] [17]
References [1] D.B. Mitzi, K. Chondroudis, C.R. Kagan, Org. Electron. 45 (2001) 29. [2] D.B. Mitzi, Progress in Inorganic Chemistry, vol. 48, Wiley, New York, 1999, p. 1. [3] M. Era, S. Morimoto, T. Tsutsui, S. Saito, Appl. Phys. Lett. 65 (1994) 676. [4] C.R. Kagan, D.B. Mitzi, C.D. Dimitrakopoulos, Science 286 (1999) 945. [5] T. Kataoka, T. Kondo, R. Ito, S. Sasaki, K. Uchida, N. Miura, Phys. B 201 (1994) 423. [6] G.C. Papavassiliou, G.A. Mousdisa, I.B. Koutselas, Synth. Met. 121 (2001) 1339. [7] (a) Anwar, X.-M. Duan, K. Komatsu, S. Okada, H. Matsuda, H. Oikawa, H. Nakanishi, Chem. Lett. (1997) 247; (b) Anwar, K. Komatsu, S. Okada, H. Oikawa, H. Matsuda, H. Nakanishi, Proc. SPIE 3796 (1999) 219; (c) Anwar, X.-M. Duan, K. Komatsu, S. Okada, H. Oikawa, H. Matsuda, H. Nakanishi, Nonlinear Opt. 22 (1999) 251; (d) Anwar, S. Okada, H. Oikawa, H. Nakanishi, Chem. Mater. 12 (2000) 1162;
[18] [19]
[20] [21] [22] [23] [24] [25] [26] [27]
2471
(e) A. Anwar, H. Kosuge, S. Okada, H. Oikawa, H. Nakanishi, Jpn. J. Appl. Phys. 40 (2001) 4213. K. Kosuge, S. Okada, H. Oikawa, H. Nakanishi, Supramol. Chem. 13 (2001) 233. K. Kosuge, S. Okada, H. Oikawa, H. Nakanishi, Mol. Cryst. Liq. Cryst. 377 (2002) 265. SIR92, A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M.C. Burla, G. Polidori, M. Camalli, J. Appl. Crystallogr. 27 (1994) 435. Crystan-GM, MAC Science, Yokohama, 1994. (a) S. Haddad, R.D. Willett, Inorg. Chem. 40 (2001) 2457; (b) S. Haddad, R.D. Willett, J. Chem. Crystallogr. 31 (2001) 37; (c) G. Pon, R. Willett, A. Prince, T. Robinson, M. Turnbull, Inorg. Chim. Acta 255 (1997) 325. (a) K. Hayase, T. Asahi, K. Gesi, Acta Crystallogr. C46 (1990) 218; (b) M.L. Werk, G. Chapuis, F.J. Zu´n˜iga, Acta Crystallogr. B46 (1990) 187; (c) W.T.A. Harrison, R.A. Howie, J. Skakle, J.L. Wardell, Acta Crystallogr. C56 (2000) e124. J. Calabrese, N.L. Jones, R.L. Harlow, N. Herron, D.L. Thorn, Y. Wang, J. Am. Chem. Soc. 113 (1991) 2328. M. Braun, W. Tuffentsammer, H. Wachtel, H.C. Wolf, Chem. Phys. Lett. 303 (1999) 157. M. Kawahara, K. Teshima, M. Rikukawa, K. Sanui, Synth. Met. 121 (2001) 1331. (a) G.V. Gridunova, E.A. Ziger, V.M. Koshkin, S.V. Lindeman, Yu.T. Struchkov, V.E. Shklover, Dokl. Akad. Nauk. SSSR 278 (1984) 656; (b) M. Geselle, H. Fuess, Z. Kristallogr., New Cryst. Struct. 212 (1997) 235; (c) A.B. Corradi, S. Bruni, F. Cariati, A.M. Ferrari, A. Sandccani, F. Srolini, P. Sgarabotto, Inorg. Chim. Acta 254 (1997) 137. M. Guloy, Z. Tang, P.B. Miranda, V.I. Srdanov, Adv. Mater. 13 (2001) 833. (a) J.G. Contreras, G.V. Seguel, B. Ungerer, W.F. Maier, F.J. Hollander, J. Mol. Struct. 102 (1983) 295; (b) M. El Essawi, R. Wartchow, H.J. Berthold, Z. Kristallogr. 212 (1997) 163; (c) M. Geselle, H. Fuess, Z. Kristallogr., New Cryst. Struct. 212 (1997) 235. D. Weber, Z. Naturforsch. 33b (1978) 1443. H. Krautcheid, F. Vielsack, Z. Anorg. Allg. Chem. 625 (1999) 562. M. Geselle, H. Fuess, Z. Kristallogr., New Cryst. Struct. 212 (1997) 237. M. Geselle, H. Fuess, Z. Kristallogr., New Cryst. Struct. 212 (1997) 243. 243. J. Emsley, Chem. Soc. Rev. 9 (1980) 91. J. Zyss, J.L. Ouder, Phys. Rev. A 26 (1982) 2028. J. Zyss, D.S. Chemla, J.F. Nicoud, J. Chem. Phys. 74 (1981) 4800. M. Shiro, M. Yamakawa, T. Kubota, Acta Crystallogr. B33 (1977) 1549.