1,8-Di­aza­bicyclo­[5.4.0]undec-7-en-8-ium bromido­(phthalocyaninato)zincate

Bartosz Przybył; Jan Janczak

doi:10.1107/S160053681401157X

. 2014 May 24;70(Pt 6):m231–m232. doi: 10.1107/S160053681401157X

1,8-Diazabicyclo[5.4.0]undec-7-en-8-ium bromido(phthalocyaninato)zincate

Bartosz Przybył ^a, Jan Janczak ^a,^*

PMCID: PMC4051024 PMID: 24940212

Abstract

The title compound, (C₉H₁₇N₂)[ZnBr(C₃₂H₁₆N₈)], contains a bromido(phthalocyaninato)zincate anion and a protonated 1,8-diazabicyclo[5.4.0]undece-7-ene cation, [DBUH]⁺. The central Zn^II atom has a distorted square-pyramidal geometry, with four isoindole N atoms of the macrocycle in equatorial positions and a bromide ion in the axial position. The latter has a relatively high displacement parameter, but no evidence for disorder was obtained. The central Zn^II atom is displaced by 0.488 (3) Å from the mean plane defined by the four isoindole N atoms. The [DBUH]⁺ cation is involved in an almost linear N—H⋯Br hydrogen bond. In the crystal, π–π interactions lead to a relatively short distance of 3.366 (3) Å between the phthalocyaninate rings.

Related literature

For background information on phthalocyanines, see: Nyokong et al. (1987 ▶); Gregory (2000 ▶); Leznoff & Lever (1996 ▶); Tedesco et al. (2003 ▶); Ormond & Freeman (2013 ▶). For related structures, see: Kobayashi et al. (1971 ▶); Mossoyan-Deneux et al. (1985 ▶); Zeng et al. (2005 ▶); Del Sole et al. (2005 ▶); Kubiak et al. (2007 ▶); Yang et al. (2008 ▶); Janczak et al. (2009 ▶, 2011 ▶); Janczak & Kubiak (2009 ▶); Li et al. (2011 ▶); Przybył & Janczak (2014 ▶).

Experimental

Crystal data

(C₉H₁₇N₂)[ZnBr(C₃₂H₁₆N₈)]
M _r = 811.05
Monoclinic,
a = 12.4336 (8) Å
b = 22.9278 (16) Å
c = 13.3267 (9) Å
β = 113.266 (4)°
V = 3490.2 (4) Å³
Z = 4
Mo Kα radiation
μ = 1.90 mm⁻¹
T = 295 K
0.35 × 0.21 × 0.19 mm

Data collection

Kuma KM-4 with CCD detector diffractometer
Absorption correction: numerical (CrysAlis RED; Oxford Diffraction, 2008 ▶) T _min = 0.562, T _max = 0.725
42041 measured reflections
8492 independent reflections
4908 reflections with I > 2σ(I)
R _int = 0.045

Refinement

R[F ² > 2σ(F ²)] = 0.057
wR(F ²) = 0.143
S = 1.00
8492 reflections
478 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.76 e Å⁻³
Δρ_min = −1.26 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2008 ▶); cell refinement: CrysAlis RED (Oxford Diffraction, 2008 ▶); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg & Putz, 2006 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablock(s) I. DOI: 10.1107/S160053681401157X/fj2673sup1.cif

e-70-0m231-sup1.cif^{(36.6KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S160053681401157X/fj2673Isup2.hkl

e-70-0m231-Isup2.hkl^{(415.4KB, hkl)}

CCDC reference: 1003951

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N10—H10⋯Br1	0.87 (2)	2.44 (2)	3.281 (4)	163 (2)

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Acknowledgments

This work was supported by the Ministry of Science and Higher Education (grant No. N N204 397540).

supplementary crystallographic information

1. Comment

Phthalocyanines and metallophthalocyanines (Pcs and MPcs) arouses interest because of exhibition of many important features which gives potential application in many fields from industry to medicine (Leznoff & Lever, 1996; Gregory, 2000). The utility of MPc complexes is limited by their relatively low solubility in the most organic solvents. The solubility of MPcs can be enhanced by substitution of the H atoms of Pc macrocycle or/and by ligation an additional ligand the the metal centre of MPcs. Both ways of modification of MPc's lead to improvment of their solubility, due to decreasing of the π···π interactions between the Pc macrocycles as well as lowering their aggregation in solution. ZnPc and its derivatives, due to strong absorption in the red region of visible radiation and high triplet quantum yield and long lifetimes, are intensively studied as potential agents in photodynamic therapy (Tedesco et al., 2003; Ormond & Freeman, 2013).

Complex 1 crystallizes as ionic compound in the centrosymmetric space group of monoclinic system. The blue-violet crystals of 1 are built up from bromido(phthalocyaninato)zinc(II) anion (ZnPcBr^-) and 1,8-diazabicyclo[5.4.0]undec-7-en-8-ium cation (DBUH⁺) (Fig. 1). Both oppositely charged units interact via N—H10···Br hydrogen-bond, in which DBUH⁺ plays role of a donor (Table 1). Due to presence of DBU that accepts H⁺, phthalocyaninato macrocyle maintains -2 oxidation state, therefore the complex 1 is diamagnetic as show the magnetic susceptibility measurements. This is in contrast to the chloro(phthalocyaninato)zinc(II) in which ZnPc is oxidised and has +1 charge, and the metal centre is coordinated by phthalocyaninato anion with π-radical character, Pc^-. (Mossoyan-Deneux et al., 1985). As an effect of monaxial Zn—Br bond formation, Zn(II) atom exhibits displacement from a plane defined by four isoindole nitrogen atoms of Pc(2-) (N₄ plane) by 0.488 (3) Å. This is a value situated in the typical range in comparison with other 4+1 complexes of ZnPc reported in the literature (Table S1). Additionally, pyramidal coordination environment of Zn(II) centre is slightly distorted, angle between the normal to the N₄ plane and the Zn—Br bond is equal 1.65 (5) ° that is inclined towards the hydrogen-bond. In reported structure Pc(2-) macrocycle has nearly flat conformation though deformation from flat to saucer-like shape is very common among 4+1 MPc complexes arranged in the back-to-back fashion in solids. Almost all nitrogen and carbon atoms of Pc(2-) exhibit displacement from the mean plane of these atoms smaller than 0.1 Å (only three peripheral carbon atoms slightly exceed this value). Complex of ZnPc with chloride (Mossoyan-Deneux et al., 1985) also exhibits nearly flat conformation of Pc(2-) macrocycle, thus deformation of the molecule into saucer-like shape is probably caused by interaction with bulky ligands like amines or pyridine derivatives (Table S1). Mutual arrangement of the complex molecules exhibits typical back-to-back fashion, with the distance 3.366 (3) Å, as a consequence of π···π interaction between Pc(2-) macrocycles. Back-to-back oriented molecules exhibits relatively small shift in plane of Pc(2-) macrorings (Fig. 2).

Thanks to DBU molecule that plays role of acceptor H⁺, ligation of ZnPc by Br^- with the formation of the ionic complex (ZnPcBr^-)(DBUH⁺) maintains -2 oxidation state of the Pc macrocycle . Thus ligation of the central Zn atom of ZnPc by Br^- in 1 does not change the colouring properties compared with the parent ZnPc pigment since the energy gap of HOMO-LUMO level is not disturbed. The Q band assigned to HOMO-LUMO transition is observed at almost the same wavelength of ~673 nm in both complexes (ZnPcBr^-)(DBUH⁺) and ZnPc (Nyokong et al., 1987). However, the ionic compound 1 is significantly better soluble than ZnPc pigment and therefore this feature of 1 widnes its potential utility.

2. Experimental

Crystals of 1 were obtained by heating of complex ZnPc—DBU, well characterized in literature (Del Sole et al. 2005, Janczak et al., 2011), with n-pentanothiol slightly acidified with HBr under solvothermal conditions (evacuated glass elongated ampoule, 130 °C, 5 days). Elemental analysis of the ionic (ZnPcBr^-)(DBUH⁺) crystals was performed with energy dispersive spectroscopy (EDS) as well as with a Perkin-Elmer 2400 elemental analyser. EDS spectra were acquired and analysed using an EDAX Pegasus XM4 spectrometer with SDD Apollo 4D detector mounted on a FEI Nova NanoSEM 230 microscope. Found: Zn, 8.00; Br, 9.95; C, 60.45; N, 17.17 and H, 4.20%. Calculated for C₄₁H₃₃N₁₀ZnBr: Zn, 8.06; Br, 9.84; C, 60.72; N, 17.27 and H, 4.10%.

The temperature dependence of the magnetic susceptibility was performed on Quantum Design SQUID magnetometer (San Diego, CA). The data were recorded at a magnetic field of 0.5 T between 1.8 and 300 K on the sample of 50 mg. Electronic absorption spectrum in solution (CARY Varian SE UV-Vis-NIR spectrometer) exhibits typical for Pc macrocycle two bands: Q (~673 nm, logε=5.55) and B (~350 nm,logε=4.22).

3. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. During refinement of the crystal structure we have seen the relatively high thermal parameters of Br coordinated to ZnPc. Therefore, the composition of the crystal has been checked with energy dispersive spectroscopy (EDS) as well as with a Perkin-Elmer 2400 elemental analyser. Elemental analysis evidently points to 1:1 proportion of Zn:Br. Therefore the refinement of the crystal structure was performed with the occupation factor of 1 for Br. Hydrogen atoms were placed in calculated positions and refined using a riding model with C—H = 0.97 Å and U_iso(H) = 1.5U_eq(C) for aliphatic and C—H = 0.93 Å and U_iso(H) = 1.2U_eq(C) for aromatic moieties. H atom involved in N—H···Br bond was localized in difference maps and refined with N—H distance restrain of 0.87 (2) Å.