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

Title Crystal Structure of Ruthenium Phthalocyanine with Diaxial Monoatomic Ligand: Bis(Triphenylphosphine) Iminium Dichloro(Phthalocyaninato(2-)) Ruthenium(III) Author(s) Yu, Derrick Ethelbhert; Kikuchi, Akira; Taketsugu, Tetsuya; Inabe, Tamotsu Citation Journal of Chemistry, 2013: 486318 Issue Date 2013 Doc URL http://hdl.handle.net/2115/51038 Rights(URL) http://creativecommons.org/licenses/by/3.0/ Type article File Information JoC2013_486318.pdf


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 solidstate arrangement that permits intermolecular - overlap for electron conduction [1,2].Moreover, the existence of strong intramolecular -d interaction in axially ligated iron(III) phthalocyanine (Fe III (Pc)L 2 ; 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].
Ab initio theoretical calculations using MOLPRO soware package [4] performed on the D 4ℎ Fe III (Pc)L 2 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 [Fe III (Pc)L 2 ] species, the Fe 3+  5  con�guration 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 multicon�gurational SCF method (active space orbitals: Pc-, Fe-  and   ; Stuttgart-Köln ECP + DZ basis) resulted in ΔE (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 Ru III (Pc)L 2 , which is electronically isostructural with the Fe III (Pc)L 2 species, the  5 homologue system resulted in a remarkable increase of around two-fold in the -d interactions across all Ru III (Pc)L 2 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 M III (Pc)L 2 , thus the importance of the synthesis of ruthenium(III) phthalocyanine with linear axial ligands.
e 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 Ru 3+ ( 5 )-centered Pc crystal has been reported.Yet, this reported Ru III (Pc)L 2 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.

Results and Discussion
e low solubility of Ru III (Pc)Cl 2 can be a cause of deterrent for the compound to be used as a precursor in synthesizing PNP[Ru III (Pc)Cl 2 ] 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[Ru III (Pc)Cl 2 ] units form ordered solid-state arrangement.Particularly, the anion component of the title compound, [Ru III (Pc)Cl 2 ] − , affords unidirectional orientation.e crystallographic parameters of PNP[Ru(Pc)Cl 2 ] are listed in Table 1.e crystal structure of PNP[Ru(Pc)Cl 2 ] is seen to be isostructural with its Fe homologue, PNP[Fe III (Pc)Cl 2 ], which also has a triclinic (  ) crystal system [3].
At the molecular level (Figure 2), the regularity is brought about by the planarity of the RuPc and the linearity of the diaxial chloro ligands which give it a uniform octahedral architecture, that is, the central Ru 3+ is aligned with the planarity of the Pc moiety which is manifested by the bond lengths, as well 0 F 1: Crystal structure of PNP[Ru III (Pc)Cl 2 ] (crystal system = triclinic; Z = 1).
as the bond angles between the central Ru 3+ 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 [Ru III (Pc)Cl 2 ] − suitable for slip-stacked intermolecular arrangement, with the cation bis(triphenylphosphine)iminium (PNP) serving as effective space-�ller in the crystal system.e resulting unidirectional and ordered orientation of [Ru III (Pc)Cl 2 ] − units is mainly attributed to the steric in�uence 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 �eld energy [3] of the axial ligands.

Conclusion
e synthesis of the crystalline PNP[Ru III (Pc)Cl 2 ] revealed an ordered octahedral structural architecture of the Ru(Pc)Cl 2 moiety.e regularity of the structure, coupled with the steric in�uence of the linear axial ligands, could effectively result in a slip-stacked arrangement capable of intermolecular - orbital overlap for electron conduction.Furthermore, PNP[Ru III (Pc)Cl 2 ] is found to be isomorphous with its Fe homologue, thus opening prospects for the solid-state synthesis of other possible Fe(Pc)L 2 homologue species of ruthenium.e resulting Ru(Pc)L 2 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.ese data can be obtained free of charge from e Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif.

S 1 :
Structure of M III (Pc)L 2 (where M = central metal and L = axial ligands).
68 H 46 N 9 Cl 2 RuP 2 ) having approximate dimensions of 0.15 × 0.10 × 0.05 mm was mounted on a glass �ber.All measurements were made on a Rigaku RAXIS RAPID imaging plate area detector with graphite monochromated Mo-K radiation.Intramolecular bond angles ( ∘ ) of PNP[Ru III (Pc)Cl 2 ].