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Cite This: Inorg. Chem. 2018, 57, 668−675

Synthesis of a Series of Monophthalocyaninato Cyclen Heavy Lanthanide(III) Complexes with Tetragonal Symmetry Kazuro Kizaki, Motoshi Uehara, Akira Fuyuhiro, Takamitsu Fukuda, and Naoto Ishikawa* Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan S Supporting Information *

ABSTRACT: A series of the new monophthalocyaninato lanthanide complexes, [Ln(Pc)(cyclen)]Cl (Ln = Y, Tb, Dy, Ho, Er, Tm, and Yb; Pc = phthalocyaninato; cyclen = 1,4,7,10-tetraazacyclododecane) was synthesized and characterized. The crystallographic study of monophthalocyaninato complexes with a capping macrocyclic ligand having no π-conjugation while keeping the 4-fold symmetry is presented for the first time. All the six complexes were crystallized in a tetragonal structure of the I4mm space group. In addition to this, the Tb complex exhibited a triclinic crystal structure of the P1̅ space group. All of the complexes are isostructural, where both Pc and cyclen are coordinated to an Ln3+ ion giving an eight-coordinate square-antiprismatic geometry. The skew angle between the Pc and cyclen ligands was 45° in the tetragonal crystals and 41.5° in the triclinic crystal. The metal−nitrogen bond lengths were shorter on the Pc ligand side than cyclen side, presumably due to the difference in the charges of the ligands and the steric factor.

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INTRODUCTION The tetradentate phthalocyainato (Pc) is well-known to form sandwich-type 2:1 complexes with a trivalent lanthanide ion formulated as [LnIII(Pc)2],1 as well as monophthalocyaninato complexes with various smaller counter ligands that fills the remaining four coordination sites.2−6 Compared to the wellstudied sandwich-type complexes, crystallographic studies on the 1:1 monophthalocyaninato complexes have been limited presumably due to the structural diversity on the counterligand side which leads to difficulty in obtaining good single crystals. Nevertheless, there has been continuous attention to their physicochemical properties in connection with potential applications as semiconductors,3 photo- or electroluminescent materials,4 and molecular magnets.5 The first report of the synthesis of monophthalocyaninato complexes was by Gurevich and Solov’ev in 1961 for europium, gadolinium, and ytterbium complexes.2a They synthesized by the reaction of corresponding lanthanide chlorides and ocyanobenzamide. Since this report, several groups have reported the synthesis and characterization of monophthalocyaninato lanthanide complexes. In 1982, Sugimoto et al. reported an alternative method in which tris(1,3-diphenyl-1,3propanedionato) lanthanide, Ln(dppd)3, is reacted with lithium phthalocyanine to give [Ln(Pc)(dppd)] and [Ln(Pc)(dppd)(dppdH)] (Pc = phthalocyaninato).2c In these complexes, the counter ligands were from corresponding starting lanthanide compounds. More recently, monophthalocyaninato complexes with the second ligands, which is different from the anions of the lanthanide compounds, have been synthesized. For example, © 2017 American Chemical Society

Gao et al. synthesized the monophthalocyaninato complex with the redox active Schiff base as the second ligand from metal-free phthalocyanine, the Schiff base, and dysprosium acetylacetonate.7 In most cases, these complexes were characterized only by absorption and NMR spectroscopy. Lomova et al. actively investigated the stability and the reactivity of monophthalocyaninato lanthanide complexes using mainly absorption spectroscopy.8 Jiazan et al. reported 1H and 13C NMR studies of [Ln(Pc)(OAc)2]H (OAc− = acetate anion) and [Ln(Pc)Cl] complexes.9 They interpreted the variation of chemical shifts of 1 H NMR spectra of these complexes using the Bleaney’s method and concluded that the acetate anion is located at the normal axial position to the phthalocyanine plane in [Ln(Pc)(OAc)2]H. To date, few reports have been published on crystallographic studies of monophthalocyaninato lanthanide complexes. Moreover, to our best knowledge, there has been no report on crystal structures of isostructural monophthalocyaninato complex series throughout the light or heavy lanthanides. De Cian et al. reported the first structural data of the monophthalocyaninato lanthanide complex formulated as [Lu(Pc)(OAc)(H2O)2]·H2O·2CH3OH in 1985.1 The lutetium ion is coordinated by two oxygen atoms of one acetate anion and two oxygen atoms of two water molecules in addition to four nitrogen atoms of the Pc ligand. Tutaß et al. reported crystallographic data of three monophthalocyaninato yttrium Received: September 29, 2017 Published: December 26, 2017 668

DOI: 10.1021/acs.inorgchem.7b02505 Inorg. Chem. 2018, 57, 668−675

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Inorganic Chemistry complexes with different counter ligands and two dimeric compounds.10 In the past decade, crystallographic studies of the complexes with the Kläui ligand,5a,11 acetylacetone and phenanthroline,12 the Schiff base,6,13 and others4b as a counter ligand have been reported to clarify the relation between the structure of the complexes and physical properties such as luminescence and magnetism. However, their low symmetric coordination environments of these complexes impede the detailed investigation of their properties. One possible strategy to obtain better crystallinity is to employ a counter ligand that can give the complex a high symmetry and less structural diversity. Recently Santria et al. established a synthesis method and reported the crystallographic data of monotetraphenylporphyrinato lanthanide complexes with a tetradentate cyclen (1,4,7,10-tetraazacyclododecane) as the second ligand.14 This complex has the strict 4fold rotational symmetry and minimal structural diversity on the counter ligand side. Here in this paper, we report a new series of a monophthalocyaninato lanthanide complex with the 4-fold symmetry, formulated as [Ln(Pc)(cyclen)]Cl (Ln = Y, Tb, Dy, Ho, Er, Tm, and Yb; Figure 1). By choosing cyclen and chloride as the second ligand and counteranion, respectively, we succeeded in establishing the preparation method and determined all crystal structures.

Scheme 1. Synthetic Route for [Ln(Pc)(cyclen)]Cl, 1−7

(Kishida Chemical Co., Ltd., neutral silica, particle size 63−200 μm). The first fraction contains bisphthalocyaninato lanthanide [Ln(Pc)2] as an impurity. After the absorption band at 460 nm of [Ln(Pc)2] disappeared, the fraction containing [Ln(Pc)Cl] was collected and concentrated by evaporation. Crystals of [Ln(Pc)(cyclen)]Cl were grown by liquid−liquid diffusion method, in which the [Ln(Pc)Cl] solution and a THF solution of excess cyclen (Tokyo Chemical Industry Co., Ltd., >97.0%) were used. After several days, red purple crystals of [Ln(Pc)(cyclen)]Cl were obtained. The elemental analysis gave a satisfactory result by adding solvent water molecules. Anal. Calcd for C40N12H36ClY + 5.4H2O (1 + 5.4H2O): C, 53.00. H, 5.20. N, 18.55. Found: C, 52.94. H, 5.14. N, 18.57. Calcd for C40N12H36ClTb + 5H2O (2 + 5H2O): C, 49.56. H, 4.78. N, 17.35. Found: C, 49.80. H, 4.69. N, 16.92. Calcd for C40N12H36ClDy+5H2O (3+5H2O): C, 49.38. H, 4.77. N, 17.28. Found: C, 49.39. H, 4.53. N, 16.94. Calcd for C40N12H36ClHo + 4.5H2O (4 + 4.5H2O): C, 49.72. H, 4.69. N, 17.40. Found: C, 49.68. H, 4.42. N, 17.13. Calcd for C40N12H36ClEr + 7.6H2O (5 + 7.6H2O): C, 46.89. H, 5.04. N, 16.41. Found: C, 46.61. H, 4.73. N, 16.73. Calcd for C40N12H36ClTm + 4.5H2O (6 + 4.5H2O): C, 49.51. H, 4.68. N, 17.33. Found: C, 49.03. H, 4.20. N, 17.81. Calcd for C40N12H36ClYb + 3.7H2O (7 + 3.7H2O): C, 50.04. H, 4.56. N, 17.51. Found: C, 49.87. H, 4.32. N, 17.95. A single crystal of [Tb(Pc)(cyclen)]Cl with another morphology (2tri) was obtained for the terbium complex by exposing its chloroform solution to the air. Measurements. UV−vis absorption spectra were recorded using a Shimadzu UV-1650Pc spectrophotometer. Mass spectra were measured with a MALDI-TOF mass spectrometer (KRATOS AXIMA-CFR, Shimadzu) using dithranol (SIGMA-Aldrich, ≥98.5%) as a matrix. Single-crystal X-ray diffraction measurements were performed on a Rigaku R-AXIS VII diffractometer equipped with an imaging plate detector (300.0 × 300.0 mm) using a filtered Mo Kα radiation (λ = 0.71075 Å, 45 kV, 55 mA). The data were collected at a temperature of 200 ± 1 K to maximum 2θ values of 55.0 or 54.9°, and corrected for Lorentz and polarization effects. The structures were solved by direct methods and expanded using Fourier techniques. The disordered non-hydrogen atoms were refined isotropically, while the nondisordered ones were refined anisotropically. Hydrogen atoms were refined using the riding model. An anomalous dispersion was considered for all non-hydrogen atoms. All calculations were performed using the CrystalStructure 4.216 crystallographic software package except for refinement, which was performed using SHELXL Version 2014/7.17 A full-matrix least-squares refinement was based on measured unique reflections.

Figure 1. Structure of [Ln(Pc)(cyclen)]+ unit.

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EXPERIMENTAL SECTION

Synthesis. General Procedure for Synthesis of Hydrous Lanthanide Chlorides. Lanthanide chlorides, LnCl3·nH2O, were prepared from the corresponding lanthanide oxides.15 The lanthanide oxide (Rare Metallic Co., Ltd., 99.99%) was dissolved in excess hydrochloric acid (Wako Pure Chemical Industries, Ltd., special grade) with heating. After removal of the solvent water by evaporation, the precipitate was collected and washed with water. The solid LnCl3· nH2O was obtained after vacuum drying. General Procedure for Synthesis of Lanthanide and Yttrium Complexes, [Ln(Pc)(cyclen)]Cl (Ln = Y (1), Tb (2), Dy (3), Ho (4), Er (5), Tm (6), and Yb (7)). [Ln(Pc)(cyclen)]Cl were synthesized via an intermediate species [Ln(Pc)Cl] as shown Scheme 1, which we prepared according to the literature with some modifications.10 Although its actual structure has not been determined, the intermediate species is most likely to contain additional ligands including solvent molecules, since trivalent lanthanides generally tend to take 8 or larger coordination number. Phthalonitrile (Merck KGaA, 98%, 40 mmol) was dissolved in 5 mL of 1-chloronaphthalene heated to 180 °C. To the solution, 4 mmol of LnCl3·nH2O was then added. The mixture was heated under reflux for 40 min or longer. After a color change associated with precipitation of a black solid, the reaction was stopped by an addition of 10 mL of 1chloronaphthalene. The resulting solution was filtrated while hot, washed with dichloromethane, and then washed with toluene using a Soxhlet extractor. The residue containing [Ln(Pc)Cl] was dissolved to tetrahydrofuran (THF) and chromatographed on a silica column

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RESULTS AND DISCUSSION Synthesis. The compounds [Ln(Pc)(cyclen)]Cl were synthesized using an intermediate complex [Ln(Pc)Cl] as described in the experimental section. On the preparation of the latter complex, presence of HCl in the lanthanide chloride

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DOI: 10.1021/acs.inorgchem.7b02505 Inorg. Chem. 2018, 57, 668−675

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Inorganic Chemistry significantly reduced the yields. Therefore, it was mandatory to carefully remove HCl from the starting material. The number of the crystal water in the lanthanide chloride, on the other hand, probably do not have noticeable influence on the reaction. It is noteworthy that the final step for the ligand substitution with cyclen proceeds under a very mild condition at room temperature. In the prior literature, the substitution reactions of the counter ligands of the Pc complexes were, in most cases, taking place at a high temperature in a high boiling-point solvent or using unstable lanthanide reagents such as Ln[N(SiMe3)2]3.11,18 In addition, the present method gives quite high purity without additional steps for purification, which is inevitable in most cases due to the presence of multiple side products. The results of elemental analysis agreed with the calculated values considering physically adsorbed waters. Differences between the calculated and experimental values were in the range of ±0.5%. Mass spectra clearly showed the presence of the cyclen complexes (Figure 2 for 1, Figures S1−S4 for 3−5 and 7). In

Figure 3. Normalized absorption spectra of 1−7 in CH2Cl2 solution.

at longer wavelength than those of [Ln(Pc)Cl], which is especially evident for the band at about 610 nm (Figure S6). Crystal Structure. All of the complexes crystallized from the THF solutions in a space group I4mm of a tetragonal symmetry with very similar lattice parameters. However, 2tri obtained from the CHCl3 solution crystallized in a space group P1̅ of a triclinic symmetry. The crystallographic data and measurement condition are summarized in Table 1 for 1−7 (details in Table S2) and Table 2 for 2tri (details in Table S3). Figures 4 and 5 show the molecular and crystal structures of 4 and 2tri, respectively. Selected bond lengths and bond angles are listed in Tables S4 and S5 for 1−7 and in Tables S6−S8 for 2tri. Hereafter, we denote the lanthanide ion and coordinating nitrogen atoms of the cyclen and Pc ligands as Ln, Ncyc, and NPc, respectively. The skew angle ω is defined as the angle between two NPc−Ln−N′Pc and Ncyc−Ln−N′cyc planes as shown in Scheme 2. In the tetragonal structure, the cyclen ligand coordinates to the lanthanide ion with 45° of a skew angle ω to the Pc ligand. The carbon atoms of the cyclen ligand labeled as C5A and C5B are disordered each other. These positions are generated by two mirror planes and the 4-fold rotation axis in the unit cell. Figure 4a shows one of two disordered molecular structures of 4. The complex has the 4-fold rotation axis perpendicular to the planes made by four NPc and that by four Ncyc. The chloride ion is disordered and in general positions in the unit cell. Figure 4b,c shows the packing structure of 4. The molecules stack in a head-to-tale manner along the c axis. First and second intermetallic distances are 7.3119(3) and 13.1812(3) Å, respectively. In contrast with the first intermetallic distance along the c axis, the second intermetallic distance corresponds to that between the center and the corner of the unit cell. The intermetallic distances do not indicate a clear tendency through the complex series. In the triclinic structure, the molecular structure is similar to that of the tetragonal structure (Figure 5b). However, there are no disordered atom in this system. The cyclen and Pc ligands coordinate to the Tb ion with the skew angle of 41.5° and form a pseudo-square-antiprism type structure. In this case, this angle is a mean value of four skew angles. The chloride ion is placed above the cyclen side of the complex and on the 4-fold axis perpendicular to the planes made by NPc atoms and that by Ncyc atoms. The chloride ion contacts with the hydrogen atoms of the cyclen ligand and two chloroform molecules. The chloride ion and two chloroform molecules fill the void of the crystal by C−H···Cl interaction. This chloride ion also interacts with two

Figure 2. Mass spectrum of 1.

each spectrum, the peaks were identified as related species of the [Ln(Pc)(cyclen)]Cl complex: In the case of 1, [Y(Pc)(cyclen)]+ at m/z = 774 and [Y(Pc)(cyclen)]Cl−H+ at 808 as shown in Figure 2. The isotopic patterns of 3, 5, and 7 agree with the patterns expected for each complexes although slight shift from the calculated values appeared, which is probably due to an instrumental systematic error (Figures S1, S3, and S4). Absorption Spectroscopy. Absorption spectra of 1−7 are shown in Figure 3. Wavelengths of the absorption band peaks are tabulated in Table S1. The complexes show the typical spectral features similar to those of monophthalocyaninato complexes such as [Mg(Pc)] and [Zn(Pc)],19 indicating that the cyclen ligand does not electronically interact with the Pc ligand in contrast to the situation of the double-decker complexes. The Q-band with the vibronic progressions and the Soret band appear at about 677 and 349 nm, respectively. The Q-band peak shows a tendency of a red shift with increasing of the atomic number as seen in Figure S5. The absorption spectra of [Ln(Pc)(cyclen)]Cl and those of [Ln(Pc)Cl] are quite similar to each other. Nevertheless, there can be seen a clear difference between them. Although the main peak of the Q-band of both complexes appears at almost same wavelengths, the vibronic bands of [Ln(Pc)(cyclen)]Cl appear 670

DOI: 10.1021/acs.inorgchem.7b02505 Inorg. Chem. 2018, 57, 668−675

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Inorganic Chemistry Table 1. Crystallographic Data for the Tetragonal [Ln(Pc)(cyclen)]Cl, 1−7 1

2

formula formula weight cryst. syst. space group a (Å) c (Å) volume (Å3) Z

C40H36N12ClY 809.16 tetragonal I4mm (#107) 18.0558(8) 7.37241(17) 2403.49(16) 2

C40H36N12ClTb 879.18 tetragonal I4mm (#107) 18.1304(16) 7.4079(4) 2435.1(3) 2

no. obsd. (all ref) no. variables R1 (I > 2σ (I)) wR2 (all ref) goodness of fit flack parameter Δρmax, Δρmin (e/A3)

1469 75 0.1776 0.4138 1.716 0.44(5) 7.37, −0.94

1540 78 0.0782 0.1961 1.284 0.42(6) 4.63, −0.62

3

4

Crystal Data C40H36N12ClDy C40H36N12ClHo 882.76 885.19 tetragonal tetragonal I4mm (#107) I4mm (#107) 18.0826(14) 17.9097(4) 7.4286(3) 7.31185(17) 2429.0(3) 2345.33(9) 2 2 Structure Solution and Refinement 1545 1428 75 75 0.1465 0.0505 0.3158 0.1460 1.544 1.250 0.43(10) 0.159(10) 15.89, −1.45 3.99, −0.54

5

6

7

C40H36N12ClEr 887.52 tetragonal I4mm (#107) 18.1197(7) 7.36018(18) 2416.53(15) 2

C40H36N12ClTm 889.19 tetragonal I4mm (#107) 17.9646(10) 7.2953(3) 2354.4(2) 2

C40H36N12ClYb 893.30 tetragonal I4mm (#107) 18.1877(14) 7.3537(3) 2432.5(3) 2

1506 75 0.0749 0.1784 1.142 0.486(6) 8.56, −0.79

1432 75 0.0819 0.2003 1.203 0.160(13) 10.05, −0.79

1533 76 0.1593 0.3605 1.332 0.489(11) 12.97, −1.76

ligand. This configuration appears at the similar structural complex, [LnTPP(cyclen)]Cl.14 In contrast, in the cases of 1− 7, if the electron density appeared in the center hole of the cyclen were assigned as a chloride ion, then the distances between the chloride and the carbon or nitrogen atoms of the cyclen would become unreasonably short. For instance, the distance between the chloride ion and the carbon atom labeled as C5A in the tetragonal system would be about 2.2 Å, which is significantly shorter than the van der Waals contact of 3.45 Å.20 Another point to be considered is the peculiarity of this position. The center of the cyclen ligand is on the 4-fold axis and two mirror planes in the tetragonal cell. It is well-known that the ghost peak of the electron density tends to appear in such special positions in the relatively high symmetry space group.21 From these reasons, we concluded that the appropriate structure is that with no chloride ion in the center of the cyclen ligand and assigned the chloride positions to the electron densities in the general positions, although the final structure has higher R factors. Several important distances in the [Ln(Pc)(cyclen)]+ unit are listed in Table 3. The interplanar distance between the planes made by four NPc and that made by four Ncyc shows clear correlation to the ionic radii22 of the lanthanides as seen in Figure 6. Ln−Ncyc and Ln−NPc distances also show an increasing trend with an increase of ionic radii of the lanthanides (Figure 7). The Ln−Ncyc distance is longer than the Ln−NPc distance in all the cases. The former lengths are in the range of 2.50(4)−2.56(3) Å and the latter is in the range of 2.32(4)−2.381(13) Å. This is presumably due to the difference in the charge of the ligand, i.e., −2 for Pc and neutral for cyclen. In addition, the N atoms of the cyclen are bound to a hydrogen atom, which is located on the near side to the metal ion. This causes a steric hindrance and thus leads to a longer Ln−N distances on the cyclen side. However, the neighboring Ncyc−Ncyc and NPc−NPc distances are nearly unchanged with increasing ionic radii and hence the size of the N square is almost kept constant (Figure 8). The Ncyc−Ncyc and NPc−NPc distances are in the ranges of 2.86(4)− 2.92(4) Å and 2.78(19)−2.84(3) Å, respectively. Thus, the coordination structure can be described as a distorted squareantiprism, in which Ncyc square is larger than that of NPc and the metal is placed closer to the NPc square.

Table 2. Crystallographic Data for the Triclinic [Tb(Pc)(cyclen)]Cl·2CHCl3, 2tri·2CHCl3 2tri·2CHCl3 Crystal Data formula C42H38N12Cl7Tb formula weight 1117.94 cryst. syst. triclinic space group P1̅ (#2) a (Å) 14.2375(7) b (Å) 15.1445(11) c (Å) 15.4654(9) α (deg) 65.240(8) β (deg) 75.094(9) γ (deg) 89.964(11) volume (Å3) 2904.3(4) Z 2 Structure Solution and Refinement no. obsd. (all ref) 13259 no. variables 559 R1 (I > 2σ (I)) 0.0954 wR2 (all ref) 0.2695 goodness of fit 1.091 Δρmax, Δρmin (e/A3) 6.54, −2.60

peripheral hydrogen atoms of Pc ligands and forms the crystal structure in which two complexes stacked antiparallel each other (Figure 5b). The first and second intermetallic distances are 8.407(12) and 10.354(10) Å, respectively. These values are different from those of the tetragonal crystals. The first intermetallic distance corresponds to that between a molecule in an unit cell and the molecule in the neighboring unit cell with opposite direction. The second distance is that between two molecules in the same unit cell. Prior to the present results for 1−7 in the tetragonal system, we examined alternative solutions for the structures giving relatively high R factors, in which a large peak of a differential electron density appears at the center of the pore of the cyclen ligand. At first, we suspected that this electron density was to be assigned to the chloride ion. However, we concluded that this electron density is the ghost peak for the following reasons. In the triclinic crystal for 2tri the chloride ion is placed 4.1 Å above the Ncyc plane, which is reasonably apart from the cyclen 671

DOI: 10.1021/acs.inorgchem.7b02505 Inorg. Chem. 2018, 57, 668−675

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Inorganic Chemistry

Figure 4. (a) Molecular structure of 4. The thermal ellipsoid plots with the probability level at 50%. C5A and C5B are disordered each other; however, one of two disordered molecular structures is showed here. Atoms in the asymmetric unit are labeled. Hydrogen atoms are omitted for clarity. (b) Crystal structure of 4 viewed along the a axis (green: the chloride anion). (c) Crystal structure of 4 viewed along the c axis.

Figure 5. (a) Molecular structure of 2tri. The thermal ellipsoid plots with the probability level at 50%. The metal ion and coordinating nitrogen atoms are labeled. Hydrogen atoms are omitted for clarity. (b) Crystal structure of 2tri viewed along the a axis.

Scheme 2. Definition of the Structural Parametersa

Comparison with the [Ln(Pc)2]− Complexes. Crystal structures of [Ln(Pc)2]TBA (TBA+ = tetrabutylammonium cation) have been reported by several authors.23,24 The structures of the [Ln(Pc)2]− complexes with different counter cations as well as neutral complexes are also reported (for example, [Ln(Pc) 2 ]PNP·xH 2 O, where PNP + = bis(triphenylphosphine)iminium cation25 and neutral [Er(Pc)2]).26 In this paper, we limit ourselves to the cases of the [Ln(Pc)2]TBA23 salt with the similar molecular and crystal structure, i.e., the orthorhombic (Pna21) and tetragonal (P4212 and P4/nmm) structures, to compare with the cyclen complexes of the tetragonal system. The lanthanide ions in [Ln(Pc)(cyclen)]Cl and [Ln(Pc)2]− are placed in the similar coordination environment of the pseudo-square-antiprism type. The difference between the two cases appears on the distances between the lanthanide ion and

a (a) Skew angle ω and N−N distances; (b) interplanar distance dN. The labels for the atoms are of the tetragonal structures.

coordinating nitrogen atoms. The Ln−Ncyc and Ln−NPc distances of the cyclen complex are longer and shorter than the Ln−NPc distance of [Ln(Pc)2]−, respectively, as seen in 672

DOI: 10.1021/acs.inorgchem.7b02505 Inorg. Chem. 2018, 57, 668−675

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Inorganic Chemistry Table 3. Several Crystallographic Values for [Ln(Pc)(cyclen)]Cl ionic radius (Å)21 Ln−Ncyc distance (Å) Ln−NPc distance (Å) first Ln−Ln distance (Å) second Ln−Ln distance (Å) neighboring Ncyc−Ncyc distance (Å) neighboring NPc−NPc distance (Å) interplanar distance (Å) A/C ratioa B/C ratioa

A B C

1

2

2tri

3

4

5

6

7

1.015 2.518 2.374 7.372 13.289 2.88 2.80 2.787 1.0334 1.0047

1.04 2.547 2.381 7.4079 13.3445 2.87 2.80 2.854 1.0056 0.9811

1.04 2.56 2.37 8.407 10.354 2.90 2.80 2.845 1.0193 0.9842

1.03 2.56 2.368 7.4286 13.3149 2.92 2.84 2.786 1.0481 1.0194

1.02 2.529 2.362 7.3119 13.1812 2.87 2.79 2.805 1.0232 0.9947

1.00 2.538 2.361 7.3602 13.3306 2.91 2.81 2.76 1.0543 1.0181

0.99 2.51 2.334 7.2953 13.2162 2.87 2.78 2.743 1.0463 1.0135

0.98 2.50 2.32 7.3537 13.3759 2.86 2.80 2.684 1.0656 1.0432

a

This ratio indicates a degree of an elongation of the coordination polyhedron. If the value is less than 1, then the polyhedron is elongated along a 4fold axis.

Figure 6. Interplanar distances of the [Ln(Pc)(cyclen)]Cl and [Ln(Pc)2]− complexes. The data of the [Y(Pc)2]− complex have been cited from ref 23a, Gd, Ho and Lu complexes from ref 23b, Tb and Dy complexes from ref 23c, the Er complex from ref 23d.

Figure 8. Neighboring N−N distances of the [Ln(Pc)(cyclen)]Cl and [Ln(Pc)2]− complexes. The data of the [Y(Pc)2]− complex have been cited from ref 23a, Gd, Ho and Lu complexes from ref 23b, Tb and Dy complexes from ref 23c, and the Er complex from ref 23d.

respectively. The first intermetallic distance of [Ln(Pc)2]− is longer than that of the cyclen complex by about 4 Å. This is caused by the difference in the packing structure: [Ln(Pc)2]− anions and TBA+ cations stack alternatingly along the c axis in the [Ln(Pc)2]TBA case, while only [Ln(Pc)(cyclen)]+ cations stack along the c axis in the [Ln(Pc)(cyclen)]Cl case. The second intermetallic distances of both complexes show relatively close values due to small influence of the TBA cation to this distance of [Ln(Pc)2]−. Comparison with the [Ln(TPP)(cyclen)]Cl Complexes. As mentioned above, the crystal and molecular structures of the porphyrin analogues, [Ln(TPP)(cyclen)]Cl, have been investigated by Santria et al.14 Although the crystal system of the porphyrin complexes (P4̅21c) is significantly different from that of the present case (I4mm), the two groups share common structural features around central lanthanide ions. Here we compare the structures of the two groups. Below we denote the coordinating nitrogen atoms of the TPP ligand as NTPP. As a representative case, a comparison of the holmium Pc and TPP complexes is shown in Figure 9. One of the noticeable differences between the two groups is that while the NTPP−NTPP distances are longer than Ncyc−Ncyc in the TPP complexes the NPc−NPc distances are shorter than the Ncyc−Ncyc in the Pc counterparts (Figures 9a,c and S7). Considering the fact that the size of the coordinating N square of TPP is generally larger than that of Pc, the above tendency is quite reasonable. Another noteworthy point is that the Ncyc−

Figure 7. Ln−N distances of the [Ln(Pc)(cyclen)]Cl and [Ln(Pc)2]− complexes. The data of the [Y(Pc)2]− complex have been cited from ref 23a, Gd, Ho and Lu complexes from ref 23b, Tb and Dy complexes from ref 23c, and the Er complex from ref 23d.

Figure 7. In contrast, the interplanar distances of the both complexes show similar dependence to the lanthanide ionic radii as seen in Figure 6. It can be said that upon changing from the double-decker complex to the mono Pc complex the lanthanide ion moves toward Pc while the height of the squareantiprism structure is almost kept. In addition to this, the cyclen side has the larger N square size than that of [Ln(Pc)2]−. In both cyclen and [Ln(Pc)2]− complexes, the shortest intermetallic distance is along the c axis. The first and second intermetallic distances of [Ho(Pc)2]− are 11.079 and 12.972 Å, 673

DOI: 10.1021/acs.inorgchem.7b02505 Inorg. Chem. 2018, 57, 668−675

Article

Inorganic Chemistry

hydrogen atoms on Ncyc, which are located on the near side to the lanthanide. The effect of lanthanide contraction has been observed through Ln−N and dN which decrease with decreasing lanthanide (III) ionic radii. However, the N−N distances are nearly unchanged with decreasing ionic radii; hence, the size of the N square is almost kept constant.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.7b02505. Mass spectra, absorption spectra, results of XRD (PDF) Accession Codes

CCDC 1559475−1559482 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

Figure 9. Ln−N and N−N distances of Ho mono-Pc and mono-TPP complexes. The N square of the top side is that of the cyclen ligand; the bottom side is Pc or TPP ligand. (a) Neighboring N−N distances of [Ho(Pc)(cyclen)]Cl. (b) Ln−N interplanar and Ln−N4 distances of [Ho(Pc)(cyclen)]Cl. (c) Neighboring N−N distances of [Ho(TPP)(cyclen)]Cl. (d) Ln−N interplanar and Ln−N4 distances of [Ho(TPP)(cyclen)]Cl. The data of [Ho(TPP)(cyclen)]Cl have been cited from ref 14

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AUTHOR INFORMATION

Corresponding Author

Ncyc distances of the TPP complexes are smaller by around 0.05 Å than those of Pc counterparts throughout all the metal cases. Metal-to-nitrogen distances, however, show a different tendency. In both groups, the Ln−Ncyc distances are significantly longer, by about 0.15 Å, than those of the counter tetrapyrrole ligands for all the metal cases (Figures 9b,d and S8). The Ln−Ncyc distances in the TPP complexes and those in the Pc counterparts take similar values, although slightly larger in the former complexes. Interestingly, the Ln−NTPP and Ln− NPc distances also take similar values, which makes a contrast to the large difference in the N square sizes. The interplanar distances, dN, of the two complex groups take close values and show similar dependence to the lanthanide ionic sizes (Figures 9b,d and S9). On the contrary, the distances from metal to N square, denoted as Ln−N4, significantly differ in the two groups (Figure S10): The Ln−N4 distances of the TPP complexes are shorter by 0.05−0.1 Å than those of the Pc counterparts. These structural differences between the two complex groups can be interpreted as a result of the N square size change from Pc to TPP while keeping both metal−nitrogen and interplanar distances. By changing from Pc to TPP, the N square becomes wider, and the lanthanide ion is drawn toward the NTPP square to keep the Ln−NTPP distance constant. To compensate this deformation while keeping Ln−Ncyc and dN, the size of the N square on the flexible cyclen side is squeezed, resulting in a smaller Ncyc−Ncyc distance in the TPP complexes.

*Phone: +81(6)6850-5408. Fax: +81(6)6850-5408. E-mail: [email protected]. ORCID

Naoto Ishikawa: 0000-0002-3490-4222 Notes

The authors declare no competing financial interest.

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REFERENCES

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CONCLUSIONS We synthesized and characterized seven new isostructural lanthanide (III) and yttrium(III) monophthalocyaninato complexes, [Ln(Pc)(cyclen)]Cl. This is the first synthesis and crystallographic report of monophthalocyaninato complexes with a nontetrapyrrole-type tetradentate counter ligand with a strict 4-fold symmetry axis. The lanthanide ion is placed in the distorted square-antiprismatic coordination environment with an elongation along the 4-fold axis. The lanthanide ion is closer to the NPc plane than the Ncyc because of the difference in the charge of the ligands and the steric hindrance due to the 674

DOI: 10.1021/acs.inorgchem.7b02505 Inorg. Chem. 2018, 57, 668−675

Article

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DOI: 10.1021/acs.inorgchem.7b02505 Inorg. Chem. 2018, 57, 668−675