Molecular structure of tetrakis(1,2,5-thiadiazolo)-porphyrazinatozinc(II) in gaseous phase Текст научной статьи по специальности «Химические науки»

Porphyrazines

Порфиразины

Макрогэтэроцмклы

Communication

Сообщение

http://macroheterocycles.isuct.ru

DOI: 10.6060/mhc170399g

Molecular Structure of Tetrakis(1r2,5-thiadiazolo)-porphyrazinatozinc(II) in Gaseous Phase

Natalia V. Tverdova,a Nina I. Giricheva,b Denis S. Savelyev,a Maksim S. Mikhailov,a Natalja Vogt,c Oscar I. Koifman,a Pavel A. Stuzhin,a and Georgiy V. Giricheva@

aIvanovo State University of Chemistry and Technology, 153000 Ivanovo, Russia bIvanovo State University, 153025 Ivanovo, Russia cUniversity of Ulm, 89069 Ulm, Germany @Corresponding author E-mail: girichev@isuct.ru

The molecular structures of gaseous zinc tetrakis(1,2,5-thiadiazolo)porphyrazine, [ZnTTDPz], and 1,2,5-thiadiazole-3,4-dicarbonitrile, C Nfi, were studied by synchronous gas-phase electron diffraction and mass spectrometric experiment at T=587(5) °C in combination with quantum chemical calculations at theory level B3LYP/cc-pVTZ. The vapour over the sample at the temperature of experiment contained molecules of complex [ZnTTDPz] and 1,2,5-thiadiazole-3,4-dicarbonitrile (C4Nfi) having the molecular symmetry D4h and Cv respectively. In contrast to the crystal structure, where Zn atom is displaced out of plane of the coordination moiety, the gaseous molecule [ZnTTDPz] has a planar structure. Geometry of the dinitrile C N S in the gas phase do not differ strongly from that in a crystal.

Keywords: 1,2,5-Thiadiazole, porphyrazine, zinc(II) complex, 1,2,5-thiadiazole-3,4-dicarbonitrile, electron diffraction, DFT, molecular structure.

Молекулярная структура тетракис(1г2,5-тиадиазоло)-порфиразината цинка(П) в газовой фазе

Н. В. Твердоват Н. И. Гиричева,ь Д. С. Савельев,а М. С. Михайлов,а Н. Фогт,с О. И. Койфман,а П. А. Стужин,а Г. В. Гиричева@

аИвановский государственный химико-технологический университет, 153000 Иваново, Россия ъИвановский государственный университет, 153025 Иваново, Россия сУльмскийуниверситет, 89069 Ульм, Германия @Е-таИ: girichev@isuct.ru

Строение молекул тетракис(1,2,5-тиадиазол)порфиразината цинка, [2пТТОР2], и 1,2,5-тиадиазол-3,4-дикарбонитрила, CN.fi, изучено в рамках синхронного электронографического/масс-спектрометрического эксперимента при температуре Т=587(5) °С в комбинации с квантово-химическими расчетами методом В3ЬУР/сс-рУТ2. При температуре эксперимента пар состоял из молекул комплекса [2пТТБР2] и динитрила CNS, имеющих симметрию 04к и С2, соответственно. В противоположность кристаллической структуре, в которой атом цинка выходит из плоскости координационной полости, газообразная молекула [ZnTTDPz] имеет плоское строение. Геометрическое строение молекулы CN.fi в газовой фазе близко к ее строению в кристалле.

Ключевые слова: 1,2,5-Тиадиазол, порфиразин, комплекс цинка, 1,2,5-тиадиазол-3,4-дикарбонитрил, газовая электронография, молекулярная структура.

Heterocyclic phthalocyanine analogues - porphyrazines with annulated 1,2,5-chalcogenadiazole rings containing peripheral S, Se or Te atoms have received an increasing attention over the last decade,[1-3] particularly due to perspectives of their application in organic electronics evidenced for tetrakis(1,2,5-thiadiazolo)porphyrazines.[45]

X-Ray study[6] of the tetrakis(thiadiazole)porphyrazine and the corresponding metal(II) derivatives ([MTTDPz], M=2H, Fe", Co11, Ni", Cu", Zn11) showed that a variety of new interunit contacts (p-p interactions, S-N electrostatic contacts, M---N coordination bonding) determines the type of molecular packing in different a, p and y solid-state forms. In crystal the structure of the molecules is disturbed due to collective interactions. In the gas phase the structure of the individual molecule can be more strictly correlated with inherent physicochemical properties.

In this work we report for the first time the results of the direct experimental molecular structural investigation of gaseous zinc(II) tetrakis(1,2,5-thiadiazole)porphyrazine, [ZnTTDPz], by synchronous gas-phase electron diffraction (GED) and mass spectrometric experiment in combination with quantum chemical DFT calculations (B3LYP/cc-pVTZ level). Previously the DFT optimization of [ZnTTDPz] molecule was performed using BP86/TZ2P basis set.[7]

The electron diffraction patterns and the mass spectra were recorded simultaneously using a combined GED/MS unit based on EMR-100 and APDM-1 devices. [8,9] The sample of [ZnTTDPz] synthesized as described previously[10] was evaporated from a molybdenum effusion cell. The evaporation temperature was measured by a W/Re-5/20 thermocouple. The electron wavelength was determined from the diffraction patterns of ZnO recorded before and after the GED experiments on [ZnTTDPz]. The total intensity curves were obtained from two nozzle-to-plate distances, Zj=598 mm and L2=338 mm.

Firstly, we have studied mass spectra of [ZnTTDPz] in the range from 1 to 2500 m/e using ionizing electron energy 50 eV at various temperatures. The typical mass spectrum recorded at 588 °C is shown in Figure 1 and the relative abundance of ions is presented in Table 1. It was found that [ZnTTDPz] has a high sublimating temperature and the molecular ion appears in the mass spectra recorded above

~500 °C. Sublimation of [ZnTTDPz] under reduced pressure (about 10-3 bar) with continuous N2 gas flow was also observed at 450-550 °C.[6] The high sublimating temperature in our more strict vacuum conditions (about 10-7 bar) is surely determined by strong intermolecular interactions present in the solid (crystalline) state of [ZnTTDPz] (especially formation of coordination polymer chains[6]).

Table 1. Relative abundance of ions from [ZnTTDPz] at conditions of GED experiment.

Iona m/e I b, % av '

[ZnNi6Ci6SJ+ 609 12

[C4N4S]+ 136 26

[N2C2S]+ 84 75

[N2CJ+ 76 32

[C3NJ+ 64 87

№]+ 52 100

^approximate assignment bmost abundant isotope

It is known that metal complexes of tetrapyrrolic macrocycles, such as phthalocyanines and porphyrins, have high thermal stability. In the absence of substituents they do not undergo decomposition during sublimation and the molecular ion is the prevailing ion in the mass spectra of their vapours. Thus, the mass spectrum of zinc phthalocyanine, [ZnPc], contains such ions as: the parent ion [ZnPc]+ (most intensive, 100 %), the intensive doubly charged parent ion [ZnPc]2+ (33 %), as well as minor fragmentation ions [Zn+^Pc]2+ (11 %), [Zn+^Pc]+ (6 %) and [^Pc]+ (4 %).["] In contrast, analyzing the mass spectra of [ZnTTDPz] recorded during GED/MS experiment we came to the conclusion that its sublimation, unlike [ZnPc], is accompanied by partial decomposition. The heaviest observed ion [ZnC16N16S4]+ at m/z=609 a.m.u. corresponding to the parent ion [ZnTTDPz]+ disappears at higher temperature or prolonged exposition. This parent ion has lower intensity than another heavy ion [C4N4S]+ at m/z=136 a.m.u. which remains in the mass spectra after disappearance of the parent ion [ZnC16N16S4]+. The [C4N4S]+ ion corresponds to ^(TTDPz) and can be

iloJUuluU

[C2N2]

[N2C2S]+

[C4N4S]+

T=588°C

[ZnNi6Ci6S4]

jji_

-1—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i

0 50 100 150 200 250 300 350 400 450 500 550 600 650

m/z

Figure 1. Typical mass spectrum (EI, 50 eV) recorded at 588 °C.

G.V. Girichev et al.

Figure 2. Molecular structures of [ZnTTDPz] and C4N4S with atom numbering.

assigned to the C4N4S molecular species - 1,2,5-thiadiazole-3,4-dicarbonitrile which presents in the vapor together with [ZnTTDPz] at the GED experiment temperature.

The electron diffraction patterns were recorded simultaneously with the mass spectrum at 587(5) °C. Final least-square analysis of the electron scattering molecular intensity was performed with the assumption that the vapour over the sample of solid zinc(II) tetrakis(1,2,5-thiadiazolo)porphyrazine consists of [ZnTTDPz] molecules and the dinitrile C4N4S as its decomposition product. The best fitting was obtained for the vapour composition

[ZnTTDPz]/N4C4S=0.1/0.9 in overall agreement with the ion intensity ratio in the mass spectrum at the same conditions.

Additionally the molecular structures of [ZnTTDPz] and C4N4S were optimized under D4h and C2v symmetry restrains, respectively, at the B3LYP/cc-pVTZ theory level using Gaussian 03 program.[12] The selected structural parameters obtained by gas electron diffraction and DFT calculations are given in the Table 2. It can be seen that the values of structural parameters produced by the analysis of GED data for both compounds existing in gas phase - the macrocyclic complex [ZnTTDPz] and the dinitrile C4N4S -are in satisfactory agreement with the available single crystal X-ray diffraction data.[613]

The results of GED refinement and DFT calculations show that the [ZnTTDPz] molecule has a planar structure of D4h symmetry in the gas phase. This indicates that the displacement of the Zn atom out of plane of the molecule found in the crystal structure of [ZnTTDPz] is caused by intermolecular interactions or more exactly by «the (M-.N) coordination bonding» as it previously was reported by Awaga et al.[6] The Zn-N coordination bond with central nitrogens in gaseous [ZnTTDPz] is shorter by ~0.02 Á than in crystalline [ZnTTDPz] due to planar structure of the macrocyclic ligand. At the same time it is longer by ~0.04 Á than in the gas-phase [ZnPc].[13] The Zn-N difference between [ZnTTDPz] and [ZnPc] reflects the effect of expansion of the macrocyclic core observed when external benzene rings in the phthalocyanines are replaced by heterocyclic 1,2,5-thiadiazole moieties in TTDPz macrocycle. It should be noted that the expansion of the macrocyclic core is accompanied by rearrangement of all

Table 2. Structural parameters of [ZnTTDPz] and C4N4S according to GED, X-ray and B3LYP/cc-pVTZ calculations.*

[ZnTTDPz]

N4C4S

Parameter GED rhi DFT r e X-ray[6] r Parameter GED rh1 DFT r e X-ray[13] r

Bond distances Bond distances

Zn-N b 2.023(12) 2.024 2.043(5) S-N Y 1.641(4) 1.636 1.623(5)

N-c ** 1 a 1.382(4) 1.375 1.380(7) N-CP Y P 1.326(4) 1.320 1.329(6)

C-N a m 1.324(4) 1.318 1.326(7) C.-C P a 1.414(6) 1.425 1.442(5)

c -c ** a P 1.448(6) 1.458 1.456(8) C -N ** am 1.159(5) 1.151 1.140(8)

CP-N P Y 1.322(4) 1.315 1.327(7)

N-S ** Y 1.658(4) 1.654 1.641(5)

CP-CP 1.411(6) 1.422 1.408(8)

Bond angles Bond angles

ZnN.C ** 1a 124.2(9) 124.2 124.0(5) NYSNY YY 98.2(10) 98.8 99.6(3)

CaC.Cp 107.7(10) 107.0 107.2(5) NYCPCP YPP 112.7(5) 113.4 113.5(3)

NCCp ** 106.5(5) 107.1 107.5(5) SNYCP YP 108.2(7) 107.2 106.7(3)

CPCPN ** P P Y 116.1(7) 115.1 114.9(5) NYCPCa YPa 122.4(6) 121.4 120.7(5)

C N C a 1 a 111.6(6) 111.7 110.6(5) CPCN Pam 180.0 fix 180.0 178.6(6)

CN C ama 124.5(7) 125.7 124.2(5)

NSN Y Y 101.8(10) 100.1 100.7(3)

* bond distances in A, bond angles in deg.

** parameters refined independently; other parameters were constrained to independent parameters

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

i.Ä"1

Figure 3. Functions of the molecular scattering intensity sM(s): experimental (dots), and theoretical (line), and the difference function AsM(s) for the vapor containing species [ZnTTDPz] and N4C4S with mole fraction ratio 0.1:0.9.

geometrical parameters of the molecule. In contrast with the above-mentioned [ZnTTDPz] molecule the GED geometry of the dinitrile molecule C4N4S in gas phase is similar to the X-Ray geometry in a crystalline state.[13]

Investigation of gas-phase behavior of other porphyrazine analogues with fused 1,2,5-thiadiazole rings is in progress.

Acknowledgements. The authors are thankful to Russian Science Foundation for support of synthetic and experimental parts (grant 14-23-00204) and to Russian Foundation for Basic Research for support of theoretical part and computational resources (grant 13-03-00975a).

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Received 20.02.2017 Accepted 16.03.2017