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

Authors: Derrick Ethelbhert Yu; Akira Kikuchi; Tetsuya Taketsugu; Tamotsu Inabe
Journal: Journal of Chemistry
 (2013)

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## Abstract

Axially-ligated iron phthalocyanines have been found to be good molecular conductors with giant negative magnetoresistance (GNMR) which originates from a strong intramolecularπ-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
π-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 [RuIII(Pc2−)Cl2]. It is observed that [RuIII(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 π-d interaction-based molecular conductors with potentially exceptional GNMR.


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## Body

## 1. Introduction

Metallophthalocyanine complexes with mono- or diatomic linear diaxial ligands (Scheme1) are suitable molecular conductors due to their ability to form a slip-stacked solid-state arrangement that permits intermolecular π-π overlap for electron conduction [1, 2]. Moreover, the existence of strong intramolecular π-d interaction in axially ligated iron(III) phthalocyanine (FeIII(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].Scheme 1
Structure ofMIII(Pc)L2 (where M = central metal and L = axial ligands).Ab initio theoretical calculations using MOLPRO software package [4] performed on the D4hFeIII(Pc)L2 system corroborated experimental observation that the strength of GNMR is directly related to the strength of π-d interaction in the order of L = CN > Cl > Br. On the electronic structure representation of [FeIII(Pc)L2] species, the Fe3+d5 configuration gives two-fold degenerate (dxy)2(dxz)2(dyz)1 = (dxy)2(dxz)1(dyz)2 while the HOMO is a singly occupied molecular orbital of the delocalized π-system of the Pc. Electronic structure calculations using two state-averaged complete active space multiconfigurational SCF method (active space orbitals: Pc-π, Fe-dxz and dyz; Stuttgart-Köln ECP + DZ basis) resulted in ΔE (orbital energy difference between dyz/dxz and HOMO; intensity of the π-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 RuIII(Pc)L2, which is electronically isostructural with the FeIII(Pc)L2 species, the d5 homologue system resulted in a remarkable increase of around two-fold in the π-d interactions across all RuIII(Pc)L2 species (L: CN = 3.7518 eV, Cl = 3.8419 eV, Br = 3.9411 eV). Given that the intensity of the unique intramolecular π-d interaction as the origin of the varying anisotropic GNMR in MIII(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+(d5)-centered Pc crystal has been reported. Yet, this reported RuIII(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),RuIII(Pc1−)Cl2, was prepared via the method reported by Myers et al. in preparing various MIII(Pc1−)Cl2 through the reaction of MII(Pc) with thionyl chloride oxidizing agent [8]. RuIIPc (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 RuIII(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[RuIII(Pc2−)Cl2], crystallized into dark blue crystals after 8 weeks.


### 2.2. X-Ray Crystal Structure Determination

A blue block crystal of PNP [RuIII(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 χ=45.0° and ϕ=0.0°. 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 χ=45.0° and ϕ=180.0°. 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].


## 2.1. Crystallization

Dichloro(phthalocyaninato(1-)) ruthenium(III),RuIII(Pc1−)Cl2, was prepared via the method reported by Myers et al. in preparing various MIII(Pc1−)Cl2 through the reaction of MII(Pc) with thionyl chloride oxidizing agent [8]. RuIIPc (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 RuIII(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[RuIII(Pc2−)Cl2], crystallized into dark blue crystals after 8 weeks.


## 2.2. X-Ray Crystal Structure Determination

A blue block crystal of PNP [RuIII(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 χ=45.0° and ϕ=0.0°. 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 χ=45.0° and ϕ=180.0°. 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 ofRuIII(Pc)Cl2 can be a cause of deterrent for the compound to be used as a precursor in synthesizing PNP[RuIII(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 Figure1, it can be observed that PNP[RuIII(Pc)Cl2] units form ordered solid-state arrangement. Particularly, the anion component of the title compound, [RuIII(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[FeIII(Pc)Cl2], which also has a triclinic (Z=1) crystal system [3].Table 1
Crystallographic data collection parameters of PNP[RuIII(Pc)Cl2] at 123 K.
Empirical formula
C68H46N9Cl2P2Ru1
Formula weight
1223.10
Crystal system
Triclinic
Lattice parameters
a =  10.4425(11)Å
b = 12.2391(11)Å
c = 13.159 (11)Å
α = 75.523(3)°
β = 64.686(3)°
γ  = 65.883(3)°
V = 1381.9(2)Å3
Space group
P
1
- (#2)
Z value
1
Calculated density
1.470 g/cm3
μ
(
MoK
α
)
4.92 cm−1
2θmax
49.0°
Reflections collected/unique
10394/4588
[R(int) = 0.1173]
R
1 [I> 2.00σ(I)]
0.0803
wR2 (all data)
0.2345
Goodness-of-fit indicator
1.105Figure 1
Crystal structure of PNP[RuIII(Pc)Cl2] (crystal system = triclinic; Z = 1).At the molecular level (Figure2), 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 [RuIII(Pc)Cl2]− suitable for slip-stacked intermolecular arrangement, with the cation bis(triphenylphosphine)iminium (PNP) serving as effective space-filler in the crystal system.Table 2
Intramolecular bond lengths (Å) of PNP[RuIII(Pc)Cl2].
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–C16
1.395(12)
N5–P1
1.552(3)
C2–C3
1.380(13)
C3–H3
0.9300
C5–C6
1.396(14)
C6–H6
0.9300
C10–C11
1.383(14)
C11–H11
0.9300
C13–C14
1.384(15)
C14–H14
0.9300
C17–C18
1.402(16)
C19–C20
1.353(19)
C20–H20
0.9300
C22–H22
0.9300
C24–C25
1.371(15)
C25–H25
0.9300
C27–C28
1.359(15)
C29–C30
1.375(13)
C30–H30
0.9300
C32–C33
1.354(14)
C33–H33
0.9300
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–N4
1.329(12)
C2–C7
1.424(13)
C4–C5
1.373(15)
C5–H5
0.9300
C7–C8
1.463(13)
C10–C15
1.417(14)
C12–C13
1.406(15)
C13–H13
0.9300
C15–C16
1.449(14)
C18–C19
1.421(18)
C19–H19
0.9300
C21–C22
1.389(18)
C23–C28
1.382(13)
C24–H24
0.9300
C26–C27
1.391(16)
C27–H27
0.9300
C29–C34
1.403(14)
C31–C32
1.390(16)
C32–H32
0.9300
C34–H34
0.9300
Ru1–N1
1.993(8)
Ru1–Cl1
2.355(3)
P1–C29
1.789(10)
N1–C8
1.392(12)
N3–C9
1.365(13)
N4–C16
1.337(12)
C1–C2
1.463(13)
C3–C4
1.379(14)
C4–H4
0.9300
C6–C7
1.373(13)
C9–C10
1.481(13)
C11–C12
1.376(14)
C12–H12
0.9300
C14–C15
1.362(13)
C17–C22
1.384(16)
C18–H18
0.9300
C20–C21
1.34(2)
C21–H21
0.9300
C23–C24
1.386(14)
C25–C26
1.404(16)
C26–H26
0.9300
C28–H28
0.9300
C30–C31
1.398(15)
C31–H31
0.9300
C33–C34
1.361(15)Table 3
Intramolecular bond angles (°) of PNP[RuIII(Pc)Cl2].
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 C9
122.7(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 H21
120.5
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 H31
119.8
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
120.2Figure 2
ORTEP molecular structure representation of PNP[RuIII(Pc)Cl2] (hydrogens are omitted for clarity).The resulting unidirectional and ordered orientation of [RuIII(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 π-π 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[RuIII(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 π-π orbital overlap for electron conduction. Furthermore, PNP[RuIII(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 π-d interactions than its Fe counterparts that could result in molecular conductors with exceptional GNMR.



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*Source: 486318-2012-10-11.xml*