Molecular Structure, Vibrational Spectrum and Conformational Properties of 4-(4-Tritylphenoxy)phthalonitrile-Precursor for Synthesis of Phthalocyanines with Bulky Substituent

By DFT method with B3LYP, PBE, CAM-B3LYP, and B97D functionals, it was found that the molecule 4-(4-tritylphenoxy)phthalonitrile (TPPN) has four conformers. The geometric structure, vibrational frequencies, electronic characteristics, and thermodynamic functions of conformers, as well as the structure and energy of transition states, were determined. IR spectrum of TPPN film contains vibrational bands belonging to different conformers. The assignment of bands was performed basing the distribution of normal vibration energy on internal coordinates. A synchronous electron diffraction/mass spectrometric experiment was performed to determine the structure of conformers in a saturated TPPN vapor. The elemental composition of the ions recorded in the mass spectrum indicates the thermal stability of TPPN at least up to T = 200 °C. The difference in the structure of tetrasubstituted metal phthalocyanines, which can be synthesized from different TPPN conformers, has been shown.


Introduction
Currently, considerable attention is paid to phthalocyanines containing bulk trityl, due to their manifestation of liquid crystal properties [1][2][3][4], as well as the prospects for their use in thin-film electronics [5]. In addition, phthalocyanine compounds with high solubility are currently needed [6,7]. An increase in solubility can be achieved by introducing substituents of a certain nature [7,8]. In [5], novel tetra (4-tritylphenoxy) substituted copper, zinc, and cobalt phthalocyanines were obtained by reaction of 4-(4-tritylphenoxy)phthalonitrile (TPPN) (Scheme 1) with CuCl 2 , ZnCl 2 , CoCl 2 metal salts (scheme in two dimensions of metal substituted phthalocyanine molecules is given in Supplementary Materials, Section S1). It has been shown in Ref. [5] that the presence of bulky 4-tritylphenoxy substituents on the peripheral positions prevents the aggregation in organic solvents, such as CHCl 3 , CH 2 Cl 2 , THF, DMF, DMSO, and adds interesting properties to phthalocyanines, such as high solubility.
It is well known that tetrasubstituted phthalocyanines are usually obtained as a mixture of four constitutional isomers [9]. This can be considered a positive or negative factor, depending on the purpose of applied phthalocyanines. For using these compounds as materials in thin films, it is even better to have an isomeric mixture that will not crystallize very easily [2]. The presence of bulky 4-tritylphenoxy substituents in the β-position can lead to regioselectivity of substituted phthalocyanines. the structure of this compound. This paper describes the first experimental study (gas electron diffrac nation with mass spectrometry, as well as IR spectroscopy) of the molecula conformational properties of 4-(4-tritylphenoxy)phthalonitrile suppleme tum chemical calculations. Scheme 1. Molecule of 4-(4-tritylphenoxy)phthalonitrile.

Conformational Analysis
The TPPN molecule has six torsion coordinates, which can give rise formers that differ in the mutual orientation of trityl, phenoxy (PhO), and (PhN) fragments. The atom numbering is shown in Figure 1. However, 4-tritylphenoxy substituents have a structural feature that is usually overlooked and which can affect the thermodynamic, spectral, and electro-optical properties of metal phthalocyanines. This feature of 4-tritylphenoxy substituents is related to the conformational properties of TPPN, which is used as the precursor for the synthesis of phthalocyanines with trityl groups as peripheral substituents.
Obtaining reliable experimental data for the 4-(4-tritylphenoxy)phthalonitrile and their subsequent study is an actual problem due to the lack of any experimental work on the structure of this compound.
This paper describes the first experimental study (gas electron diffraction in combination with mass spectrometry, as well as IR spectroscopy) of the molecular structure and conformational properties of 4-(4-tritylphenoxy)phthalonitrile supplemented by quantum chemical calculations.

Conformational Analysis
The TPPN molecule has six torsion coordinates, which can give rise to several conformers that differ in the mutual orientation of trityl, phenoxy (PhO), and phthalonitrile (PhN) fragments. The atom numbering is shown in Figure 1. very easily [2]. The presence of bulky 4-tritylphenoxy substituents in the β-position can lead to regioselectivity of substituted phthalocyanines. However, 4-tritylphenoxy substituents have a structural feature that is usually overlooked and which can affect the thermodynamic, spectral, and electro-optical properties of metal phthalocyanines. This feature of 4-tritylphenoxy substituents is related to the conformational properties of TPPN, which is used as the precursor for the synthesis of phthalocyanines with trityl groups as peripheral substituents.
Obtaining reliable experimental data for the 4-(4-tritylphenoxy)phthalonitrile and their subsequent study is an actual problem due to the lack of any experimental work on the structure of this compound. This paper describes the first experimental study (gas electron diffraction in combination with mass spectrometry, as well as IR spectroscopy) of the molecular structure and conformational properties of 4-(4-tritylphenoxy)phthalonitrile supplemented by quantum chemical calculations. Scheme 1. Molecule of 4-(4-tritylphenoxy)phthalonitrile.

Conformational Analysis
The TPPN molecule has six torsion coordinates, which can give rise to several conformers that differ in the mutual orientation of trityl, phenoxy (PhO), and phthalonitrile (PhN) fragments. The atom numbering is shown in Figure 1. To determine the structure of the found conformers ( Figure 2) and the barriers between them, the potential functions of internal rotation were calculated (B3LYP/cc-pVTZ): Around the CO1-O (Figure 3  To determine the structure of the found conformers ( Figure 2) and the barriers between them, the potential functions of internal rotation were calculated (B3LYP/cc-pVTZ): Around the C O1 -O (Figure 3), C t -C O4 (Figure 4), C N1 -O ( Figure 5) bonds, and around C t -C t1 bond in the trityl group. The φ[C O2 C O1 OC N1 ], φ[C O3 C O4 C t C t1 ], and φ[C O1 OC N1 C N2 ] dihedral angles were scanned with a step of 2 • or 10 • .         (Table 1) has a similar form. In cis-conformers, the CO1-O bond eclipses the CN1-CN2 bond, whereas in trans-conformers, the dihedral angle CO1OCN1CN2 is approximately 180°. As a result, cisconformers I and II differ from the corresponding trans-conformers III and IV by the position of the C≡N substituents in the phthalonitrile moiety ( Figure 2).    (Table 1) has a similar form. In cis-conformers, the C O1 -O bond eclipses the C N1 -C N2 bond, whereas in trans-conformers, the dihedral angle C O1 OC N1 C N2 is approximately 180 • . As a result, cis-conformers I and II differ from the corresponding trans-conformers III and IV by the position of the C≡N substituents in the phthalonitrile moiety ( Figure 2). The barrier between cis-conformers I and II and, accordingly, between trans-conformers III and IV is practically the same and amounts to 6.3 kcal/mol. In transition states TSI → II and TSIII → IV the dihedral angle ϕ[CO2CO1OCN1] between the planes of the PhO and PhN fragments is close to 0° (Figures 2 and 3).
The second way of the transition between conformers I→II and III→IV can be realized by rotating the PhO-PhN fragment around the CO4-Ct bond. In this case, in the TSI → II and TSIII → IV transition states, strong steric interaction occurs between PhO and trityl C(Ph)3 fragments, which leads to a high energy barrier > 16 kcal/mol ( Figure 4).
The difference in the two cis-conformers I and II, as well as in the two trans-conformers III and IV, lies in the different orientation of the PhN group relative to trityl fragment, namely, in conformers I and III, the dihedral angle CO2CO1OCN1 should be defined as φ = +99°, and in conformers II and IV φ = −95° ( Figure 3, Table 1). Figure 5 demonstrates that cis→trans transition can be realized by rotation of the PhN fragment around the O-CN1 bond. The energy barrier between the cis-conformer II and trans-conformer IV is 5.6 kcal/mol and corresponds to TSII → IV in which the bond angle CO1-O-CN1 between the PhO and PhN fragments is 118°, and dihedral angle ϕ[CO1OCN1CN2] is 90°.
Additional calculations were carried out to estimate the barrier of internal rotation of the phenyl ring of the trityl group around the Ct-Ct1 bond. It has been shown that an independent rotation by ~40° of one of the phenyl fragments leads to a strong steric repulsion between the Ph fragments in trityl. As a result, the phenyl rings cannot rotate but perform synchronous torsional vibrations. The amplitude of these vibrations Δϕ depends on the thermal energy RT and is estimated as ±16° at T = 298 K and ±18° at T = 478 K. The barrier between cis-conformers I and II and, accordingly, between trans-conformers III and IV is practically the same and amounts to 6.3 kcal/mol. In transition states TSI → II and TSIII → IV the dihedral angle ϕ[CO2CO1OCN1] between the planes of the PhO and PhN fragments is close to 0° (Figures 2 and 3).
The second way of the transition between conformers I→II and III→IV can be realized by rotating the PhO-PhN fragment around the CO4-Ct bond. In this case, in the TSI → II and TSIII → IV transition states, strong steric interaction occurs between PhO and trityl C(Ph)3 fragments, which leads to a high energy barrier > 16 kcal/mol ( Figure 4).
The difference in the two cis-conformers I and II, as well as in the two trans-conformers III and IV, lies in the different orientation of the PhN group relative to trityl fragment, namely, in conformers I and III, the dihedral angle CO2CO1OCN1 should be defined as φ = +99°, and in conformers II and IV φ = −95° ( Figure 3, Table 1). Figure 5 demonstrates that cis→trans transition can be realized by rotation of the PhN fragment around the O-CN1 bond. The energy barrier between the cis-conformer II and trans-conformer IV is 5.6 kcal/mol and corresponds to TSII → IV in which the bond angle CO1-O-CN1 between the PhO and PhN fragments is 118°, and dihedral angle ϕ[CO1OCN1CN2] is 90°.
Additional calculations were carried out to estimate the barrier of internal rotation of the phenyl ring of the trityl group around the Ct-Ct1 bond. It has been shown that an independent rotation by ~40° of one of the phenyl fragments leads to a strong steric repulsion between the Ph fragments in trityl. As a result, the phenyl rings cannot rotate but perform synchronous torsional vibrations. The amplitude of these vibrations Δϕ depends on the thermal energy RT and is estimated as ±16° at T = 298 K and ±18° at T = 478 K. The barrier between cis-conformers I and II and, accordingly, between trans-conformers III and IV is practically the same and amounts to 6.3 kcal/mol. In transition states TS I→II and TS III→IV the dihedral angle φ[C O2 C O1 OC N1 ] between the planes of the PhO and PhN fragments is close to 0 • (Figures 2 and 3).

The General Structural Motives and Electronic Characteristics of Conformers
The second way of the transition between conformers I→II and III→IV can be realized by rotating the PhO-PhN fragment around the C O4 -C t bond. In this case, in the TS I→II and TS III→IV transition states, strong steric interaction occurs between PhO and trityl C(Ph) 3 fragments, which leads to a high energy barrier > 16 kcal/mol ( Figure 4).
The difference in the two cis-conformers I and II, as well as in the two trans-conformers III and IV, lies in the different orientation of the PhN group relative to trityl fragment, namely, in conformers I and III, the dihedral angle C O2 C O1 OC N1 should be defined as ϕ = +99 • , and in conformers II and IV ϕ = −95 • (Figure 3, Table 1). Figure 5 demonstrates that cis→trans transition can be realized by rotation of the PhN fragment around the O-C N1 bond. The energy barrier between the cis-conformer II and trans-conformer IV is 5.6 kcal/mol and corresponds to TS II→IV in which the bond angle C O1 -O-C N1 between the PhO and PhN fragments is 118 • , and dihedral angle φ[C O1 OC N1 C N2 ] is 90 • .
Additional calculations were carried out to estimate the barrier of internal rotation of the phenyl ring of the trityl group around the C t -C t1 bond. It has been shown that an independent rotation by~40 • of one of the phenyl fragments leads to a strong steric repulsion between the Ph fragments in trityl. As a result, the phenyl rings cannot rotate but perform synchronous torsional vibrations. The amplitude of these vibrations ∆φ depends on the thermal energy RT and is estimated as ±16 • at T = 298 K and ±18 • at T = 478 K.

The General Structural Motives and Electronic Characteristics of Conformers
Theoretical calculations performed using four DFT functionals lead to consistent results. All variants of the DFT method predict the presence of four C 1 symmetry conformers for the TPPN molecule. For identical molecular forms, the differences in the corresponding internuclear distances do not exceed 0.002 Å, in the values of bond angles 1 • , and less than 7 • in the values of torsion angles (Table S1).
All conformers have a similar structure of (Ph) 3 C(PhO) fragment. The central site C(C) 4 is a distorted tetrahedron with identical C-C bonds, two C-C-C bond angles that are smaller than the tetrahedral one, and four C-C-C bond angles larger than the tetrahedral one (Table S1). The bond lengths and bond angles in this fragment are the same in all conformers. Differences are observed in the values of torsion angles of cisand transconformers as well as bond lengths in the PhN fragment. In addition, in conformers I and III, the shortest distance H···H between the hydrogen atoms of the trityl group and the phthalonitrile PhN fragment is~3.7 Å and in conformers II and IV~4.1 Å. Table 1 shows the selected characteristics of conformers of 4-(4-tritylphenoxy)phthalonitrile molecule according to DFT/B3LYP/cc-pVTZ (Table S2 shows the characteristics of the conformers calculated with the functionals B97D, CAM-B3LYP, PBE).
All conformers have close energies of frontier orbitals and large dipole moments (Table 1), however, the direction of dipole moments in cis-conformers differs significantly from their direction in trans-conformers. Figure 6 shows the frontier MOs of conformer II. At the electron transition from HOMO to LUMO, the electron density is transferred from the trityl fragment to phthalonitrile PhN. The frontier orbitals of other conformers have a similar form. All conformers have a similar structure of (Ph)3C(PhO) fragment. The central site C(C)4 is a distorted tetrahedron with identical C-C bonds, two C-C-C bond angles that are smaller than the tetrahedral one, and four C-C-C bond angles larger than the tetrahedral one (Table S1). The bond lengths and bond angles in this fragment are the same in all conformers. Differences are observed in the values of torsion angles of cis-and trans-conformers as well as bond lengths in the PhN fragment. In addition, in conformers I and III, the shortest distance H···H between the hydrogen atoms of the trityl group and the phthalonitrile PhN fragment is ~3.7 Å and in conformers II and IV ~4.1 Å. Table 1 shows the selected characteristics of conformers of 4-(4-tritylphenoxy)phthalonitrile molecule according to DFT/B3LYP/cc-pVTZ (Table S2 shows the characteristics of the conformers calculated with the functionals B97D, CAM-B3LYP, PBE).
All conformers have close energies of frontier orbitals and large dipole moments (Table 1), however, the direction of dipole moments in cis-conformers differs significantly from their direction in trans-conformers. Figure 6 shows the frontier MOs of conformer II. At the electron transition from HOMO to LUMO, the electron density is transferred from the trityl fragment to phthalonitrile PhN. The frontier orbitals of other conformers have a similar form.  Table 1 lists the relative energies of conformers ∆Etotal, relative Gibbs free energies ΔG°T, and mole fractions χi of conformers in saturated vapor calculated for T = 298 K and T = 478 K (the latter corresponds to the temperature of the GED experiment). The difference in the ratio of ∆Etotal and ΔG°T for the four conformers is due to the entropy factor.
The conformers have close electronic energies. The difference in total energy ΔE between conformers I-IV does not exceed 0.4 kcal/mol. This increases the probability that the 4-(4-tritylphenoxy)phthalonitrile may contain different conformations in the unit crystal cell and have a complex conformational composition of the gas phase (Tables 1 and  S2). Since the barriers between conformers are quite high and exceed 5 kcal/mol, conformational transitions are unlikely even at the temperature of GED experiment (the thermal energy RT is less than 1 kcal/mоl). Thus, conformational diversity may arise during the synthesis of a compound.
In this case, the mixture of conformers should be characteristic of both the condensed and gas phases. We tried to find the validity of this assumption when interpreting the IR spectra and GED data.

Vibrational Spectrum
The infrared spectrum for the films of TPPN is shown in Figure 7, along with the calculated spectrum for a mixture of cis-and trans-conformers.  Table 1 lists the relative energies of conformers ∆E total , relative Gibbs free energies ∆G • T , and mole fractions χ i of conformers in saturated vapor calculated for T = 298 K and T = 478 K (the latter corresponds to the temperature of the GED experiment). The difference in the ratio of ∆E total and ∆G • T for the four conformers is due to the entropy factor. The conformers have close electronic energies. The difference in total energy ∆E between conformers I-IV does not exceed 0.4 kcal/mol. This increases the probability that the 4-(4-tritylphenoxy)phthalonitrile may contain different conformations in the unit crystal cell and have a complex conformational composition of the gas phase (Tables 1 and S2). Since the barriers between conformers are quite high and exceed 5 kcal/mol, conformational transitions are unlikely even at the temperature of GED experiment (the thermal energy RT is less than 1 kcal/mol). Thus, conformational diversity may arise during the synthesis of a compound.
In this case, the mixture of conformers should be characteristic of both the condensed and gas phases. We tried to find the validity of this assumption when interpreting the IR spectra and GED data.

Vibrational Spectrum
The infrared spectrum for the films of TPPN is shown in Figure 7, along with the calculated spectrum for a mixture of cisand trans-conformers. The harmonic vibrational frequencies were calculated for the fully optimized geometries of I-IV conformers at B3LYP/cc-pVTZ level. Analysis of the calculated IR spectra showed that the spectra of the two conformers I and II (cis) and two conformers III and IV (trans) almost coincide ( Figure S1).
In Table 2, the experimental vibrational frequencies νexp of TPPN recorded in this work and in [5] are compared with the calculated frequencies ωtheor, which have the highest intensity in the corresponding spectral region for cis-and trans-conformers (Figure 7). Table 2. Experimental (νexp) and theoretical (ωtheor) vibrational frequencies for cis-and trans-conformers of 4-(4-tritylphenoxy)phthalonitrile 1,2,3 . The harmonic vibrational frequencies were calculated for the fully optimized geometries of I-IV conformers at B3LYP/cc-pVTZ level. Analysis of the calculated IR spectra showed that the spectra of the two conformers I and II (cis) and two conformers III and IV (trans) almost coincide ( Figure S1).
In Table 2, the experimental vibrational frequencies ν exp of TPPN recorded in this work and in [5] are compared with the calculated frequencies ω theor , which have the highest intensity in the corresponding spectral region for cisand trans-conformers (Figure 7).
The values of the experimental frequencies ν exp in the two works are in good agreement with each other. However, in Ref. [5], low-intensity bands at 1419, 1311, and 1033 cm −1 were not noted, and an erroneous assignment of the frequency at 1253 cm −1 to the C-O-C bending vibration was given.
The correctness of the assignment of frequencies was checked on the basis of the dependencies ω theor = f(ν exp ), which had a linear character with a correlation coefficient almost equal to 1 (Figure 8). For all frequencies of normal vibrations, the distribution of potential energy (DPE) over internal vibrational coordinates is calculated. For this, the VibModule [10] program was used. The last column of Table 2 shows the natural coordinates that make the maxi-   For all frequencies of normal vibrations, the distribution of potential energy (DPE) over internal vibrational coordinates is calculated. For this, the VibModule [10] program was used. The last column of Table 2 shows the natural coordinates that make the maximum contributions to an individual normal vibration.
The relative intensities are indicated for the vibrational bands. The assignment for all 168 vibrational frequencies of the four conformers of the TPPN molecule is given in Table S3.
It should be noted that most bands in the IR spectrum possess a mixed nature (Table 2) The main differences between the calculated IR spectra of the cisand trans-conformers are in the intensity of the band at 1566 cm −1 as well as the presence of characteristic bands at 1311 cm −1 , 1442 cm −1 belonging to cis-conformers, and 1033 cm −1 , 1419 cm −1 belonging to trans-conformers ( Table 2).
The bands at 1442 cm −1 (cis) and 1419 cm −1 (trans) correspond mainly to the stretching vibrations of the C-C bonds in the phthalonitrile fragment. It should be noted that the r(C N3 -C N4 ) PhN bond length in cis-conformers is shorter than in trans-conformers (Table 3), which is reflected in the difference in the ν(C-C) PhN frequency.
An analysis of the recorded vibrational frequencies allows us to conclude that the IR spectrum indicates the presence of the cisand trans-conformers of TPPN in the condensed state.

GED Structural Analysis
Geometry of each conformer of the TPPN molecule possessed C 1 symmetry and was described by 79 independent parameters. To reduce the correlation, the number of independent parameters was restricted to 14: C t -C O4 , C O4 -C O3 , O-C O1 , C N3 -C, C-N, C t2 -H bond distances, C O4 C t C t1 , C O3 C O4 C t , C O2 C O3 C O4 , C N1 OC O1 , C t3 C t2 H valence angles, and C O3 C O4 C t C t1 , C N1 OC O1 C O2 , and C t1 C t C O4 C t1 dihedral angles (Figure 1). The remaining 65 independent parameters were linked to the above-mentioned 14 parameters by the difference between non-equivalent structural parameters of the same type obtained from B3LYP/cc-pVTZ calculations.
VibModule program [10] was applied to calculate the vibrational corrections ∆r = r h1 − r a and the starting values of root-mean-square vibrational amplitudes of each conformer at the temperature of the GED experiment using the harmonic approximation and also taking into account the non-linear interrelation between internal and Cartesian vibrational coordinates. Starting values of the geometrical parameters and vibrational amplitudes were taken from B3LYP/cc-pVTZ calculations. The dependent parameters were determined in terms of the geometrically consistent r h1 -structure. The amplitudes were refined in groups corresponding to the different peaks on the radial distribution curve. The analysis of the electron diffraction intensities was carried out using the modified KCED-35 program [11].
Theory predicts that despite the different mutual orientations of the phthalonitrile and trithyl groups, the corresponding bond lengths and most nonbonded distances of conformers I-IV are very close. This indicates that the electron diffraction intensities may be insensitive to the conformational composition of this compound.
The calculated Gibbs free energies at the temperature of the GED experiment 478 K indicate that the ratio between the mole fractions of the cisand trans-conformers in the gas phase is close to 1 (Table 1). In addition, DFT calculations predict that the cis I and trans IV forms predominate in vapor over the cis II and tarns III forms.  To assess the ability of the GED method to identify TPPN conformers I-IV, the theoretical functions sM(s) were calculated separately for each conformer based on structural parameters (bond lengths, angles, vibrational amplitudes, and shrinkage corrections) obtained using B3LYP/cc-pVTZ level ( Figure S2), as well as theoretical radial distribution functions f(r) (Figure S3). Only a small difference in the f(r) functions is observed in the range of 3-8 Å for the cisand trans-conformers.
The least-squares analysis of GED experimental intensities was performed under the assumption that the vapor contains separate conformers, as well as under the assumption that the vapor contains cisand trans-conformers in mole percent of 30/70, 50/50, and 70/30. In these versions of the least squares analysis, the value of the disagreement factor R f varied in the range of 4.13-4.28%. In accordance with the Hamilton criterion at 0.05 significance level [12], GED data do not allow giving preference to any variant of the vapor composition. Despite the lack of success in the experimental solution of the conformational problem of TPPN, the GED method still allows us to obtain reliable structural parameters of the molecule. Table 3 shows that the calculated geometric parameters of equilibrium configurations of cisand trans-conformers agree satisfactorily with the experimental ones.
The comparison of the experimental functions sM(s) and f(r) with the theoretical curves for the mole percent of 50/50 cis/trans vapor model are shown in Figures 9 and 10, respectively.  The performed analysis of IR spectra, data, and the results of quantum chemical calculations indicates the existence of cis-and trans-conformers of TPPN, both in the condensed and in the gaseous state, and GED/MS data do not contradict this conclusion. Figure 11 shows examples of positions of 4-tritylphenoxy substituents that can occur in tetrasubstituted metal phthalocyanines (MPc) during their synthesis by reaction of cis-  The performed analysis of IR spectra, data, and the results of quantum chemical calculations indicates the existence of cis-and trans-conformers of TPPN, both in the condensed and in the gaseous state, and GED/MS data do not contradict this conclusion. Figure 11 shows examples of positions of 4-tritylphenoxy substituents that can occur in tetrasubstituted metal phthalocyanines (MPc) during their synthesis by reaction of cis- The performed analysis of IR spectra, data, and the results of quantum chemical calculations indicates the existence of cisand trans-conformers of TPPN, both in the condensed and in the gaseous state, and GED/MS data do not contradict this conclusion. Figure 11 shows examples of positions of 4-tritylphenoxy substituents that can occur in tetrasubstituted metal phthalocyanines (MPc) during their synthesis by reaction of cis-(a) or trans-conformers (b) 4-(4-tritylphenoxy)phthalonitrile with metal salts. There are significant differences in the structure of the MPc conformers (a and b), which can lead to a difference in their physicochemical properties. Thus, for tetra-cis-substituted MPcs, there is a high probability of manifestation of regioselectivity, which reduces the steric repulsion between adjacent bulky substituents (Figure 11a). In the case of tetra-trans-substituted MPcs, regioisomers are possible. In addition, the possibility of the formation of tetrasubstituted MPcs with different cisand trans-orientations of 4-tritylphenoxy substituents within the same metal complex cannot be ruled out. (a) or trans-conformers (b) 4-(4-tritylphenoxy)phthalonitrile with metal salts. There are significant differences in the structure of the MPc conformers (a and b), which can lead to a difference in their physicochemical properties. Thus, for tetra-cis-substituted MPcs, there is a high probability of manifestation of regioselectivity, which reduces the steric repulsion between adjacent bulky substituents (Figure 11a). In the case of tetra-trans-substituted MPcs, regioisomers are possible. In addition, the possibility of the formation of tetrasubstituted MPcs with different cis-and trans-orientations of 4-tritylphenoxy substituents within the same metal complex cannot be ruled out. A series of copper (4-tritylphenoxy)phthalocyanines was synthesized in [4]. The authors note that the synthesized compounds exhibit mesomorphic properties and suggest that their mesomorphism originates from thermal fluctuations due to the free rotation of the bulky substituents. However, our data on barriers of internal rotations (Figures 3-5) show that the assertion of the authors of [4] about the free rotation of phenoxy and trityl groups is untenable. Nevertheless, it seems that the copper(II) phenoxy(phthalocyaninato) complex with trans-oriented 4-tritylphenoxy substituents has no serious steric obstacles to the formation of a columnar mesophase (Figure 11b).

Synthesis
Synthesis of TPPN was carried out according to the scheme used in [7,13], which is closely repeated in [4] and is described in detail in Supplementary Materials (Section S1).
A series of copper (4-tritylphenoxy)phthalocyanines was synthesized in [4]. The authors note that the synthesized compounds exhibit mesomorphic properties and suggest that their mesomorphism originates from thermal fluctuations due to the free rotation of the bulky substituents. However, our data on barriers of internal rotations (Figures 3-5) show that the assertion of the authors of [4] about the free rotation of phenoxy and trityl groups is untenable. Nevertheless, it seems that the copper(II) phenoxy(phthalocyaninato) complex with trans-oriented 4-tritylphenoxy substituents has no serious steric obstacles to the formation of a columnar mesophase (Figure 11b).

Synthesis
Synthesis of TPPN was carried out according to the scheme used in [7,13], which is closely repeated in [4] and is described in detail in Supplementary Materials (Section S1).
The product was characterized by mass spectrometry (LDI-TOF, negative mode), 1 H NMR (CDCl 3 ), 13 C NMR (CDCl 3 ), FTIR spectrum, and elemental analysis methods. The results are given in Supplementary Materials Section S1.

The Infrared Spectrum
IR spectrum was recorded for the films deposited from a solution on the KRS-5 slides in the range of 400-4000 cm −1 using an Avatar 360 FTIR spectrometer. (Details in Section 2.2).

Synchronous Gas Electron Diffraction and Mass Spectrometric Experiment
The gas phase electron diffraction patterns and mass spectra were recorded simultaneously using the technique described in Refs. [14,15] at two nozzle-to-plate distances (338 and 598 mm). The conditions of the synchronous gas-phase electron diffraction/mass spectrometric (GED/MS) experiments are shown in Table S4.
The electron wavelength was obtained by polycrystalline ZnO. The optical densities were measured by a computer-controlled modified MD-100 microdensitometer [16] with a step of 0.1 mm along the diagonal of the plate. A 10 × 130 mm region was scanned. The number of equidistant scan lines was 33. The total intensity curves were obtained in the ranges s = 1.3-16.7 Å −1 and s = 3.0-28.6 Å −1 .
Simultaneously with the registration of electron diffraction patterns, the mass spectra of TPPN vapors were recorded. According to the mass spectrometric data, only TPPN is present in the vapor, no volatile impurities are observed. Table 4 shows that the mass spectra of electron ionization (U ioniz = 50 V) contain signals of the parent ion  Table 4. Most intensive ions in mass spectrum of TPPN recorded during the GED experiment at 478 K (U ioniz = 50 V).