Journal of Chemistry

Journal of Chemistry / 2013 / Article

Research Article | Open Access

Volume 2013 |Article ID 486318 | https://doi.org/10.1155/2013/486318

Derrick Ethelbhert Yu, Akira Kikuchi, Tetsuya Taketsugu, Tamotsu Inabe, "Crystal Structure of Ruthenium Phthalocyanine with Diaxial Monoatomic Ligand: Bis(Triphenylphosphine)Iminium Dichloro(Phthalocyaninato(2-))Ruthenium(III)", Journal of Chemistry, vol. 2013, Article ID 486318, 6 pages, 2013. https://doi.org/10.1155/2013/486318

Crystal Structure of Ruthenium Phthalocyanine with Diaxial Monoatomic Ligand: Bis(Triphenylphosphine)Iminium Dichloro(Phthalocyaninato(2-))Ruthenium(III)

Academic Editor: Mitsushiro Nomura
Received27 Jun 2012
Accepted06 Sep 2012
Published11 Oct 2012

Abstract

Axially-ligated iron phthalocyanines have been found to be good molecular conductors with giant negative magnetoresistance (GNMR) which originates from a strong intramolecular -d interaction between the metal and phthalocyanine. Ab initio theoretical calculations showed that substitution of ruthenium into the phthalocyanine complex would result in a significant increase in the -d interaction of the system, potentially intensifying GNMR. This paper presents the crystal preparation and X-ray structural characterization of bis(triphenylphosphine)iminium dichloro(phthalocyaninato(2-))ruthenium(III), PNP [ (Pc2−)Cl2]. It is observed that [ (Pc2−)Cl2] system has a symmetric planar RuPc unit with perpendicular axial ligands which results in a unidirectional and uniform solid-state arrangement, suitable for -d interaction-based molecular conductors with potentially exceptional GNMR.

1. Introduction

Metallophthalocyanine complexes with mono- or diatomic linear diaxial ligands (Scheme 1) are suitable molecular conductors due to their ability to form a slip-stacked solid-state arrangement that permits intermolecular - overlap for electron conduction [1, 2]. Moreover, the existence of strong intramolecular -d interaction in axially ligated iron(III) phthalocyanine ( (Pc)L2; where L = CN, Cl, Br) molecular conductors has resulted in anisotropic giant negative magnetoresistance (GNMR) of up to 95% decrease in electrical resistance at 15 Tesla [3].

486318.sch.001

Ab initio theoretical calculations using MOLPRO software package [4] performed on the (Pc)L2 system corroborated experimental observation that the strength of GNMR is directly related to the strength of -d interaction in the order of L = CN > Cl > Br. On the electronic structure representation of [ (Pc)L2] species, the configuration gives two-fold degenerate ( )2( )2( )1 = ( )2( )1( )2 while the HOMO is a singly occupied molecular orbital of the delocalized -system of the Pc. Electronic structure calculations using two state-averaged complete active space multiconfigurational SCF method (active space orbitals: Pc- , Fe- and ; Stuttgart-Köln ECP + DZ basis) resulted in (orbital energy difference between / and HOMO; intensity of the -d interaction) of 8.5450 eV, 8.3839 eV, and 7.8655 eV for L = Br, Cl, and CN, respectively. Using the same theoretical calculation framework to (Pc)L2, which is electronically isostructural with the (Pc)L2 species, the homologue system resulted in a remarkable increase of around two-fold in the -d interactions across all L2 species (L: CN = 3.7518 eV, Cl = 3.8419 eV, Br = 3.9411 eV). Given that the intensity of the unique intramolecular -d interaction as the origin of the varying anisotropic GNMR in (Pc)L2, thus the importance of the synthesis of ruthenium(III) phthalocyanine with linear axial ligands.

The synthesis of crystalline ruthenium phthalocyanine Ru(Pc) complexes has long been a challenge in phthalocyanine chemistry. Even upon the report of pure Ru(Pc) synthesis more than three decades ago, the ambiguities of its solid-state/materials science still remain as only very few crystal structures of 6-coordinated axially ligated Ru(Pc) complexes have been reported [5, 6]. However, these Ru(Pc) complexes have bulky and/or unsymmetrical axial ligands unsuitable for structure-property correlation studies. To date, only one axially-ligated magnetic Ru3+( )-centered Pc crystal has been reported. Yet, this reported (Pc)L2 crystal has unsymmetrical mixed axial cyano and pyridine ligands from an attempted identical di-axial ligation synthesis [7]. Herein, we report the crystal structure of ruthenium(III) phthalocyanine with identical di-axial linear ligands which can form symmetrical octahedral architecture that could be a potential component for magnetotransport material application.

2. Methodology

2.1. Crystallization

Dichloro(phthalocyaninato(1-)) ruthenium(III), (Pc1−)Cl2, was prepared via the method reported by Myers et al. in preparing various (Pc1−)Cl2 through the reaction of (Pc) with thionyl chloride oxidizing agent [8]. Pc (500 mg; 0.81 mmol) synthesized using the procedure of Farrell et al. [9], was suspended in nitrobenzene (10 mL). Thionyl chloride (2 mL; 28 mmol) was subsequently added to the reaction vessel and refluxed at 70°C for 3 hours. A 1 : 10 mole ratio of (Pc1−)Cl2 and bis(triphenylphosphine) iminium chloride (PNPCl) was dissolved in a 1 : 1 : 1 : 1 (volume) dimethylformamide : acetone : ethanol : hexane solvent system. The resulting solution was then left in an evacuated dessicator compartment at 25°C. Bis(triphenylphosphine)iminium dichloro(phthalocyaninato(2-)) ruthenium(III), PNP[ (Pc2−)Cl2], crystallized into dark blue crystals after 8 weeks.

2.2. X-Ray Crystal Structure Determination

A blue block crystal of PNP [ (Pc2−)Cl2] (Formula: C68H46N9Cl2RuP2) having approximate dimensions of 0.15 × 0.10 × 0.05 mm was mounted on a glass fiber. All measurements were made on a Rigaku RAXIS RAPID imaging plate area detector with graphite monochromated Mo-Kα radiation. Indexing was performed from 3 oscillations that were exposed for 90 seconds. The crystal-to-detector distance was 127.40 mm. The data were collected at a temperature of 123 K to a maximum 2θ value of 49.0°. A total of 44 oscillation images were collected. A sweep of data was done using ω scans from 130.0 to 190.0° in 5.0° step, at ° and °. The exposure rate was 150.0 [sec/°]. A second sweep was performed using ω scans from 0.0 to 160.0° in 5.0° step, at ° and °. The exposure rate was 150.0 [sec/°]. The crystal-to-detector distance was 127.40 mm. Readout was performed in the 0.100 mm pixel mode. All post measurement data processing was performed using the CrystalStructure crystallographic software package [10].

3. Results and Discussion

The low solubility of (Pc)Cl2 can be a cause of deterrent for the compound to be used as a precursor in synthesizing PNP[ (Pc)Cl2] salt crystal. However, the difficulty can be overcome by a delicate mixture of 1 : 1 : 1 : 1 dimethylformamide : acetone : ethanol : hexane crystallization solvent which produced the title compound.

In Figure 1, it can be observed that PNP[ (Pc)Cl2] units form ordered solid-state arrangement. Particularly, the anion component of the title compound, [ (Pc)Cl2], affords unidirectional orientation. The crystallographic parameters of PNP[Ru(Pc)Cl2] are listed in Table 1. The crystal structure of PNP[Ru(Pc)Cl2] is seen to be isostructural with its Fe homologue, PNP[ (Pc)Cl2], which also has a triclinic ( ) crystal system [3].


Empirical formulaC68H46N9Cl2P2Ru1
Formula weight1223.10
Crystal systemTriclinic
Lattice parametersa = 10.4425(11)Å
b = 12.2391(11)Å
c = 13.159 (11)Å
= 75.523(3)°
= 64.686(3)°
= 65.883(3)°
= 1381.9(2)
Space group (#2)
Z value1
Calculated density1.470 g/cm3
4.92 cm−1
2 49.0°
Reflections collected/unique10394/4588
[R(int) = 0.1173]
[ > 2.00 (I)]0.0803
wR2 (all data)0.2345
Goodness-of-fit indicator1.105

At the molecular level (Figure 2), the regularity is brought about by the planarity of the RuPc and the linearity of the di-axial chloro ligands which give it a uniform octahedral architecture, that is, the central Ru3+ is aligned with the planarity of the Pc moiety which is manifested by the bond lengths, as well as the bond angles between the central Ru3+ and its adjacent nitrogen atoms being nearly equal (Tables 2 and 3). Furthermore, there is a linear 180° bond angle between the two axial chloro ligands which are perpendicular (90° ± 1.6) with respect to the central metal (Table 3), making [ (Pc)Cl2] suitable for slip-stacked intermolecular arrangement, with the cation bis(triphenylphosphine)iminium (PNP) serving as effective space-filler in the crystal system.


Atom Distance

Ru1–N3 1.982(9)
Ru1–N1 1.993(8)
P1–N5 1.552(3)
P1–C23 1.796(10)
N2–C8 1.335(12)
N3–C161.395(12)
N5–P11.552(3)
C2–C31.380(13)
C3–H30.9300
C5–C6 1.396(14)
C6–H60.9300
C10–C111.383(14)
C11–H110.9300
C13–C141.384(15)
C14–H140.9300
C17–C181.402(16)
C19–C201.353(19)
C20–H200.9300
C22–H220.9300
C24–C251.371(15)
C25–H250.9300
C27–C281.359(15)
C29–C301.375(13)
C30–H300.9300
C32–C331.354(14)
C33–H330.9300
Ru1–N3 1.982(9)
Ru1–Cl1 2.355(3)
P1–C17 1.767(12)
N1–C1 1.363(12)
N2–C9 1.349(12)
N4–C1 1.329(12)
C1–N41.329(12)
C2–C7 1.424(13)
C4–C51.373(15)
C5–H50.9300
C7–C81.463(13)
C10–C151.417(14)
C12–C131.406(15)
C13–H130.9300
C15–C161.449(14)
C18–C191.421(18)
C19–H190.9300
C21–C221.389(18)
C23–C281.382(13)
C24–H240.9300
C26–C271.391(16)
C27–H270.9300
C29–C341.403(14)
C31–C321.390(16)
C32–H320.9300
C34–H340.9300
Ru1–N11.993(8)
Ru1–Cl12.355(3)
P1–C291.789(10)
N1–C81.392(12)
N3–C91.365(13)
N4–C161.337(12)
C1–C21.463(13)
C3–C41.379(14)
C4–H40.9300
C6–C71.373(13)
C9–C101.481(13)
C11–C121.376(14)
C12–H120.9300
C14–C151.362(13)
C17–C221.384(16)
C18–H180.9300
C20–C211.34(2)
C21–H210.9300
C23–C241.386(14)
C25–C261.404(16)
C26–H260.9300
C28–H280.9300
C30–C311.398(15)
C31–H310.9300
C33–C341.361(15)


Atom Angle

N3 Ru1 N3 179.999(1)
N3 Ru1 N1 90.3(3)
N3 Ru1 Cl1 90.4(2)
N1 Ru1 Cl1 91.6(2)
N1 Ru1 Cl1 91.6(2)
N5 P1 C17 110.3(4)
N5 P1 C23 111.2(3)
C1 N1 C8 109.8(8)
C8 N2 C9122.7(8)
C16 N3 Ru1 125.7(6)
N4 C1 N1 128.8(9)
C3 C2 C7 120.0(9)
C4 C3 C2 117.9(10)
C5 C4 C3 122.2(10)
C4 C5 C6 121.2(10)
C7 C6 C5 117.3(10)
C6 C7 C2 121.4(9)
N2 C8 N1 127.7(9)
N2 C9 N3 128.3(9)
C11 C10 C15 120.9(9)
C12 C11 C10 117.3(10)
C11 C12 C13 122.0(10)
C14 C13 C12 120.2(10)
C15 C14 C13 118.5(10)
C14 C15 C10 121.1(10)
N4 C16 N3 126.1(9)
C22 C17 C18 118.3(12)
C17 C18 C19 119.0(13)
C20 C19 C18 119.4(14)
C21 C20 C19 122.7(16)
C20 C21 C22 119.0(14)
C17 C22 C21 121.6(13)
C28 C23 C24 118.8(10)
C25 C24 C23 121.6(11)
C24 C25 C26 118.8(11)
C27 C26 C25 119.2(11)
C28 C27 C26 120.7(11)
C27 C28 C23 120.8(10)
C30 C29 C34 119.9(10)
C29 C30 C31 118.9(11)
C32 C31 C30 120.4(10)
C33 C32 C31 119.4(10)
C32 C33 C34 121.6(11)
C33 C34 C29 119.7(10)
N3 Ru1 N1 89.7(3)
N3 Ru1 N1 89.7(3)
N3 Ru1 Cl1 89.6(2)
N3 Ru1 Cl1 89.6(2)
N1 Ru1 Cl1 88.4(2)
N5 P1 C29 110.5(3)
C17 P1 C23 107.7(5)
C1 N1 Ru1 124.6(6)
C9 N3 C16 108.0(8)
C1 N4 C16 124.3(8)
N4 C1 C2 122.3(9)
C3 C2 C1 133.3(9)
C4 C3 H3 121.1
C5 C4 H4 118.9
C4 C5 H5 119.4
C7 C6 H6 121.4
C6 C7 C8 132.2(9)
N2 C8 C7 124.0(9)
N2 C9 C10 122.0(9)
C11 C10 C9 133.3(10)
C12 C11 H11 121.3
C11 C12 H12 119.0
C14 C13 H13 119.9
C15 C14 H14 120.7
C14 C15 C16 132.3(10)
N4 C16 C15 123.9(9)
C22 C17 P1 119.1(9)
C17 C18 H18 120.5
C20 C19 H19 120.3
C21 C20 H20 118.7
C20 C21 H21120.5
C17 C22 H22 119.2
C28 C23 P1 122.3(8)
C25 C24 H24 119.2
C24 C25 H25 120.6
C27 C26 H26 120.4
C28 C27 H27 119.6
C27 C28 H28 119.6
C30 C29 P1 122.1(8)
C29 C30 H30 120.5
C32 C31 H31119.8
C33 C32 H32 120.3
C32 C33 H33 119.2
C33 C34 H34 120.2
N3 Ru1 N1 90.3(3)
N1 Ru1 N1 179.999(1)
N1 Ru1 Cl1 88.4(2)
N3 Ru1 Cl1 90.4(2)
Cl1 Ru1 Cl1 179.999(1)
C17 P1 C29 108.2(5)
C29 P1 C23 108.8(5)
C8 N1 Ru1 125.4(6)
C9 N3 Ru1 126.1(7)
P1 N5 P1 179.999(1)
N1 C1 C2 108.9(8)
C7 C2 C1 106.6(8)
C2 C3 H3 121.1
C3 C4 H4 118.9
C6 C5 H5 119.4
C5 C6 H6 121.4
C2 C7 C8 106.3(8)
N1 C8 C7 108.3(8)
N3 C9 C10 109.7(9)
C15 C10 C9 105.8(9)
C10 C11 H11 121.3
C13 C12 H12 119.0
C12 C13 H13 119.9
C13 C14 H14 120.7
C10 C15 C16 106.5(8)
N3 C16 C15 109.9(9)
C18 C17 P1 122.6(9)
C19 C18 H18 120.5
C18 C19 H19 120.3
C19 C20 H20 118.7
C22 C21 H21 120.5
C21 C22 H22 119.2
C24 C23 P1 119.0(8)
C23 C24 H24 119.2
C26 C25 H25 120.6
C25 C26 H26 120.4
C26 C27 H27 119.6
C23 C28 H28 119.6
C34 C29 P1 118.0(7)
C31 C30 H30 120.5
C30 C31 H31 119.8
C31 C32 H32 120.3
C34 C33 H33 119.2
C29 C34 H34 120.2

The resulting unidirectional and ordered orientation of [ (Pc)Cl2] units is mainly attributed to the steric influence of small and linear axial ligands of the fully conjugated planar Pc from which electrical and magnetic property manifestations can be designed and modulated based on its bulkiness for corresponding intermolecular - overlap variations [11], as well as on the chemical properties founded on the ligand field energy [3] of the axial ligands.

4. Conclusion

The synthesis of the crystalline PNP[ (Pc)Cl2] revealed an ordered octahedral structural architecture of the Ru(Pc)Cl2 moiety. The regularity of the structure, coupled with the steric influence of the linear axial ligands, could effectively result in a slip-stacked arrangement capable of intermolecular - orbital overlap for electron conduction. Furthermore, PNP[ (Pc)Cl2] is found to be isomorphous with its Fe homologue, thus opening prospects for the solid-state synthesis of other possible Fe(Pc)L2 homologue species of ruthenium. The resulting Ru(Pc)L2 is expected to have stronger -d interactions than its Fe counterparts that could result in molecular conductors with exceptional GNMR.

Appendix

CCDC 864862 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif.

Acknowledgments

This work was supported by the Hokkaido University Global Center of Excellence (GCOE) Program in chemistry and materials science (2007-2012) funded by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of the Japan Government.

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Copyright © 2013 Derrick Ethelbhert Yu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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