Crystal structure and DFT study of 8-hy­droxy-1,2,3,5,6,7-hexa­hydro­pyrido[3,2,1-ij]quinoline-9-carbaldehyde

Faizi, M.S.H.; Dege, N.; Malysheva, M.L.

doi:10.1107/S2056989017005886

research communications

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 73| Part 5| May 2017| Pages 791-794

https://doi.org/10.1107/S2056989017005886

Open

access

Crystal structure and DFT study of 8-hydroxy-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinoline-9-carbaldehyde

Md. Serajul Haque Faizi,^a Necmi Dege ^b and Maria L. Malysheva ^c ^*

^aDepartment of Chemistry, College of Science, Sultan Qaboos University, PO Box 36 Al-Khod 123, Muscat, Oman, ^bOndokuz Mayıs University, Arts and Sciences Faculty, Department of Physics, 55139 Samsun, Turkey, and ^cDepartment of Chemistry, Taras Shevchenko National University of Kyiv, 64, Vladimirska Str., Kiev 01601, Ukraine
^*Correspondence e-mail: maria_malysheva@mail.univ.kiev.ua

Edited by P. C. Healy, Griffith University, Australia (Received 22 March 2017; accepted 19 April 2017; online 28 April 2017)

In the title compound, C₁₃H₁₅NO₂, the fused non-aromatic rings of the julolidine moiety adopt envelope conformations. The hydroxy group forms an intramolecular hydrogen bond to the aldehyde O atom, generating an S(6) ring motif. Weak intermolecular C—H⋯O hydrogen bonds help to stabilize the crystal structure. Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) level are compared with the experimentally determined molecular structure in the solid state.

Keywords: crystal structure; 8-hydroxyjulolidine; julolidine; hydrogen bonding.

CCDC reference: 1533792

1. Chemical context

Julolidine is chemically an aniline derivative with two N-alkyl substituents forming rings back to the aromatic ring; the fused rings lock the nitrogen lone-pair of electrons into conjugation with the aromatic ring leading to unusual reactivity. The presence of the julolidine ring system in some molecules makes them useful for chromogenic naked-eye detection of copper, zinc, iron and aluminium ions as well as fluoride ions (Wang et al., 2013 ; Choi et al., 2015 ; Kim et al., 2015 ; Jo et al., 2015 ). Julolidine dyes exhibit excited-state intramolecular proton transfer (Nano et al., 2015 ). Compounds containing lulolidine rings are also used as fluorescent probes for the measurement of cell-membrane viscosity. Julolidine-based materials are also used as red emitters in OLEDs when linked to dicyanomethylpyran modules (Lee, et al., 2012 ). The julolidine unit plays an important role as it has strong electronic-donating properties for chelating (Nano, et al., 2013 ). Julolidine malononitrile acts as a `push–pull' molecule with large hyperpolarizability and is used as a model system for understanding the non-linear optical properties of molecules (Mennucci et al., 2009 ).

There are many reports in the literature on julolidine-based Schiff bases and their applications as sensors for metal ions (Park et al., 2014 ; Lee et al., 2014 ; Kim et al., 2016 ). The present work is a part of an ongoing structural study of Schiff bases based on the julolidine ring system (Faizi et al., 2016 , 2017 ). We report here the crystal structure and DFT computational calculation of the title julolidine compound (I). The results of calculations by density functional theory (DFT) on (I) carried out at the B3LYP/6–311 G(d,p) level are compared with the experimentally determined molecular structure in the solid state.

2. Structural commentary

The molecular structure of the title compound (I) is shown in Fig. 1. The π-conjugated system is nearly planar, with a 2.5 (1)° twist between the aromatic and aldehyde groups. The julolidine ring system comprises three fused rings and one locked nitrogen atom. The C1—O1 and C3—O2 bond lengths are of 1.231 (3) and 1.345 (3) Å, respectively, indicate double- and single-bond character for these bonds. The two fused non-aromatic rings of the julolidine moiety adopt slightly distorted envelope conformations with atoms C9 and C12 displaced from the plane through the remaining ring atoms by 0.654 (2) and 0.648 (2) Å, respectively. The intramolecular O2—H2⋯O1 hydrogen bond forms an S(6) ring motif (Fig. 1 and Table 1) between the phenol and aldehyde groups. Such an intramolecular hydrogen bond is common in salicylaldehyde derivatives, and the metrical parameters are comparable to those for related structures such as hydroxybenzaldehyde (Kirchner et al., 2011 ).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O1	0.82	1.89	2.621 (2)	148
C9—H9A⋯O2ⁱ	0.97	2.50	3.324 (3)	143
C9—H9B⋯O1ⁱⁱ	0.97	2.55	3.438 (3)	152
O2—H2⋯O1	0.82	1.89	2.621 (2)	148
C9—H9A⋯O2ⁱ	0.97	2.50	3.324 (3)	143
C9—H9B⋯O1ⁱⁱ	0.97	2.55	3.438 (3)	152
Symmetry codes: (i) x, y+1, z; (ii) -x+1, -y+1, -z+1.

Figure 1
The molecular structure of the title compound, with the atom labelling. Displacement ellipsoids are drawn at the 30% probability level. The intramolecular O—H⋯O hydrogen bond is shown as a dashed line (see Table 1

3. Supramolecular features

In the crystal, molecules are linked by C—H⋯O hydrogen bonds, forming an A–B--A–B–A–B arrangement through the inversion centre and propagating along the c-axis direction (see Fig. 2 and Table 1). There are no other significant intermolecular contacts present in the molecule.

Figure 2
A view of the A–B–A–B–A–B arrangement in the crystal structure of the title compound. The hydrogen bonds are shown as dashed lines (see Table 1

). For clarity, only the H atoms involved in hydrogen bonding have been included. The packing structure exhibits R₂²(16) and R₄⁴(10) graph-set motifs.

4. DFT study

The DFT quantum-chemical calculations were performed at the B3LYP/6–311 G(d,p) level (Becke, 1993 ; Lee et al., 1988 ) as implemented in GAUSSIAN09 (Frisch et al., 2009 ). DFT structure optimization of (I) was performed starting from the X-ray geometry and the values compared with experimental values (see Table 2). From these results we can conclude that basis set 6–311 G(d,p) is well suited in its approach to the experimental data.

Table 2
Comparison of selected geometric data for (I) (Å, °) from calculated (DFT) and X-ray data

Bonds	X-ray	B3LYP/6–311G(d,p)
C1—O1	1.231 (3)	1.231
C3—O2	1.345 (3)	1.345
C1—C2	1.431 (3)	1.431
N1—C5	1.381 (2)	1.381
O1—C1—C2	126.2 (2)	126.22
C1—C2—C3	121.34 (18)	120.25
C11—N1—C10	116.83 (15)	116.81

The DFT study of (I) shows that the HOMO and LUMO are localized in the plane extending from the whole julolidine ring to the salicylaldehyde ring. The electron distribution of the HOMO-1, HOMO, LUMO and the LUMO+1 energy levels are shown in Fig. 3. The molecular orbital of HOMO contain both σ and π character whereas HOMO-1 is dominated by π-orbital density. The LUMO is mainly composed of σ density while LUMO+1 has both σ and π electronic density. The HOMO–LUMO gap was found to be 0.154 a.u. and the frontier molecular orbital energies, E_HOMO and E_LUMO were f −0.19624 and −0.04201 a.u., respectively.

Figure 3
Electron distribution of the HOMO-1, HOMO, LUMO and the LUMO+1 energy levels for (I)

5. Database survey

A search of the Cambridge Structural Database (CSD, Version 5.37, update May 2016; Groom et al., 2016 ) gave 121 hits for the julolidine moiety. Of these, six have an OH group in position 8, and four also have a C=N group in position 1. The very similar compound 2-[(2,3,6,7-tetrahydro-1H,5H-benzo[ij]-quinolizin-9-yl)methylene]propanedinitrile (II) reported by Liang et al. (2009 ) has the aldehydic group in (I) replaced by dicyanovinyl groups and the hydroxy group replaced by hydrogen. The N1—C5 bond length [1.381 (2) Å] in the title compound is longer than in (II) [1.365 (3) Å] due to conjugation with dicyanovinyl group. In the julolidine-1,6-dione compound reported by Wu et al. (2007 ), the N atom of the julolidine moiety lies approximately in the plane of the benzene ring with a deviation of 0.023 (2) Å, similar to that in title compound [0.043 (2) Å], as might be expected for the maximum conjugation normally found for N-atom substituents on benzene rings.

6. Crystallization

2,3,6,7-Tetrahydro-8-hydroxy-1H,5H-benzo[ij]quinolizine-9-carboxaldehyde was purchased from Sigma Aldrich and crystallized by slow evaporation of methanol solution over a period of 2-3 days to yield quality crystal suitable for X-ray data collection.

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. All H atoms were located from difference-Fourier maps but in the final cycles of refinement they were included in calculated positions and treated as riding atoms: O—H = 0.84 Å, C—H = 0.93–0.98 Å with U_iso(H) = 1.5U_eq(O) and 1.2U_eq(C) for other H atoms.

Table 3
Experimental details

Crystal data
Chemical formula	C₁₃H₁₅NO₂
M_r	217.26
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	8.546 (3), 9.137 (3), 13.662 (4)
β (°)	95.984 (6)
V (Å³)	1061.0 (6)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.09
Crystal size (mm)	0.18 × 0.15 × 0.11

Data collection
Diffractometer	Bruker SMART CCD area detector
Absorption correction	Multi-scan (SADABS; Sheldrick, 2004 )
T_min, T_max	0.985, 0.991
No. of measured, independent and observed [I > 2σ(I)] reflections	5787, 2083, 1530
R_int	0.026
(sin θ/λ)_max (Å⁻¹)	0.617

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.066, 0.231, 1.11
No. of reflections	2083
No. of parameters	145
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.64, −0.27
Computer programs: SMART and SAINT (Bruker, 2003 ), SHELXTL and SHELXL97 (Sheldrick, 2008 ).

Supporting information

CCDC reference: 1533792

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989017005886/hg5485sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017005886/hg5485Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989017005886/hg5485Isup3.cml

checkCIF report

Computing details top

Data collection: SMART (Bruker, 2003); cell refinement: SMART (Bruker, 2003); data reduction: SAINT (Bruker, 2003); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

8-Hydroxy-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinoline-9-carbaldehyde top

Crystal data top

C₁₃H₁₅NO₂	F(000) = 464
M_r = 217.26	D_x = 1.360 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 8.546 (3) Å	Cell parameters from 1494 reflections
b = 9.137 (3) Å	θ = 2.4–28.1°
c = 13.662 (4) Å	µ = 0.09 mm⁻¹
β = 95.984 (6)°	T = 100 K
V = 1061.0 (6) Å³	Needle, colorless
Z = 4	0.18 × 0.15 × 0.11 mm

Data collection top

Bruker SMART CCD area detector diffractometer	2083 independent reflections
Radiation source: sealed tube	1530 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.026
phi and ω scans	θ_max = 26.0°, θ_min = 2.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 2004)	h = −10→10
T_min = 0.985, T_max = 0.991	k = −8→11
5787 measured reflections	l = −16→16

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.066	H-atom parameters constrained
wR(F²) = 0.231	w = 1/[σ²(F_o²) + (0.1465P)² + 0.0857P] where P = (F_o² + 2F_c²)/3
S = 1.11	(Δ/σ)_max < 0.001
2083 reflections	Δρ_max = 0.64 e Å⁻³
145 parameters	Δρ_min = −0.27 e Å⁻³

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
O2	0.73084 (18)	0.25645 (16)	0.53899 (11)	0.0398 (5)
H2	0.691533	0.226583	0.587471	0.060*
O1	0.58740 (18)	0.27075 (18)	0.69921 (11)	0.0460 (5)
N1	0.83012 (18)	0.7058 (2)	0.37861 (11)	0.0288 (5)
C5	0.7743 (2)	0.6300 (2)	0.45521 (12)	0.0242 (5)
C4	0.7801 (2)	0.4768 (2)	0.45803 (13)	0.0269 (5)
C6	0.7080 (2)	0.7115 (2)	0.53120 (14)	0.0277 (5)
C2	0.6517 (2)	0.4816 (2)	0.60979 (14)	0.0282 (5)
C7	0.6468 (2)	0.6333 (2)	0.60434 (14)	0.0282 (5)
H7	0.599815	0.684412	0.652391	0.034*
C3	0.7204 (2)	0.4032 (2)	0.53505 (14)	0.0282 (5)
C10	0.8409 (2)	0.8646 (2)	0.37928 (14)	0.0333 (6)
H10A	0.840281	0.899757	0.312243	0.040*
H10B	0.939673	0.893952	0.415420	0.040*
C11	0.9103 (2)	0.6288 (2)	0.30450 (15)	0.0330 (6)
H11A	1.020944	0.618318	0.327631	0.040*
H11B	0.902214	0.685601	0.244223	0.040*
C13	0.8464 (2)	0.3888 (2)	0.37783 (14)	0.0336 (6)
H13A	0.786287	0.299427	0.365792	0.040*
H13B	0.954748	0.362366	0.398627	0.040*
C8	0.7061 (3)	0.8758 (2)	0.52940 (15)	0.0359 (6)
H8A	0.797720	0.912690	0.569753	0.043*
H8B	0.613101	0.910814	0.557226	0.043*
C1	0.5867 (2)	0.4043 (3)	0.68718 (15)	0.0358 (6)
H1	0.539410	0.460267	0.732734	0.043*
C12	0.8388 (2)	0.4791 (2)	0.28373 (14)	0.0330 (6)
H12A	0.895351	0.428934	0.235680	0.040*
H12B	0.730055	0.489689	0.256334	0.040*
C9	0.7061 (3)	0.9339 (2)	0.42599 (15)	0.0389 (6)
H9A	0.718103	1.039438	0.427433	0.047*
H9B	0.607130	0.910495	0.387813	0.047*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O2	0.0514 (11)	0.0255 (10)	0.0406 (9)	−0.0001 (6)	−0.0050 (7)	0.0021 (6)
O1	0.0469 (11)	0.0421 (11)	0.0470 (10)	−0.0075 (7)	−0.0054 (7)	0.0141 (7)
N1	0.0304 (9)	0.0301 (11)	0.0264 (9)	−0.0015 (7)	0.0044 (7)	−0.0016 (6)
C5	0.0233 (10)	0.0269 (13)	0.0217 (10)	−0.0009 (7)	−0.0011 (8)	−0.0033 (7)
C4	0.0289 (12)	0.0273 (12)	0.0233 (11)	0.0013 (7)	−0.0034 (8)	−0.0030 (7)
C6	0.0278 (11)	0.0275 (12)	0.0270 (10)	0.0021 (8)	−0.0007 (8)	−0.0016 (8)
C2	0.0263 (11)	0.0314 (13)	0.0256 (11)	−0.0007 (8)	−0.0041 (8)	0.0020 (8)
C7	0.0289 (11)	0.0307 (13)	0.0244 (10)	0.0010 (8)	−0.0005 (8)	−0.0043 (8)
C3	0.0286 (12)	0.0220 (11)	0.0319 (12)	0.0005 (7)	−0.0069 (9)	−0.0005 (8)
C10	0.0408 (13)	0.0294 (13)	0.0298 (11)	−0.0084 (8)	0.0032 (9)	0.0002 (8)
C11	0.0290 (11)	0.0437 (14)	0.0264 (11)	0.0013 (9)	0.0036 (8)	−0.0040 (9)
C13	0.0372 (13)	0.0295 (13)	0.0332 (12)	0.0069 (8)	−0.0002 (9)	−0.0071 (8)
C8	0.0484 (14)	0.0272 (13)	0.0323 (12)	0.0008 (9)	0.0050 (9)	−0.0049 (8)
C1	0.0291 (12)	0.0411 (14)	0.0353 (12)	−0.0037 (9)	−0.0051 (9)	0.0087 (9)
C12	0.0329 (12)	0.0389 (13)	0.0265 (11)	0.0085 (9)	0.0001 (8)	−0.0099 (8)
C9	0.0543 (14)	0.0252 (12)	0.0368 (12)	−0.0019 (9)	0.0028 (10)	−0.0026 (9)

Geometric parameters (Å, º) top

O2—C3	1.345 (3)	C10—H10A	0.9700
O2—H2	0.8200	C10—H10B	0.9700
O1—C1	1.231 (3)	C11—C12	1.512 (3)
N1—C5	1.381 (2)	C11—H11A	0.9700
N1—C10	1.454 (3)	C11—H11B	0.9700
N1—C11	1.461 (2)	C13—C12	1.523 (3)
C5—C4	1.401 (3)	C13—H13A	0.9700
C5—C6	1.441 (3)	C13—H13B	0.9700
C4—C3	1.390 (3)	C8—C9	1.509 (3)
C4—C13	1.516 (3)	C8—H8A	0.9700
C6—C7	1.376 (3)	C8—H8B	0.9700
C6—C8	1.502 (3)	C1—H1	0.9300
C2—C7	1.389 (3)	C12—H12A	0.9700
C2—C3	1.423 (3)	C12—H12B	0.9700
C2—C1	1.431 (3)	C9—H9A	0.9700
C7—H7	0.9300	C9—H9B	0.9700
C10—C9	1.513 (3)

C3—O2—H2	109.5	N1—C11—H11B	109.5
C5—N1—C10	121.51 (16)	C12—C11—H11B	109.5
C5—N1—C11	120.49 (19)	H11A—C11—H11B	108.1
C10—N1—C11	116.83 (15)	C4—C13—C12	109.65 (17)
N1—C5—C4	120.54 (16)	C4—C13—H13A	109.7
N1—C5—C6	118.7 (2)	C12—C13—H13A	109.7
C4—C5—C6	120.79 (17)	C4—C13—H13B	109.7
C3—C4—C5	119.32 (17)	C12—C13—H13B	109.7
C3—C4—C13	119.00 (19)	H13A—C13—H13B	108.2
C5—C4—C13	121.66 (17)	C6—C8—C9	111.45 (16)
C7—C6—C5	117.6 (2)	C6—C8—H8A	109.3
C7—C6—C8	121.81 (17)	C9—C8—H8A	109.3
C5—C6—C8	120.62 (17)	C6—C8—H8B	109.3
C7—C2—C3	118.46 (18)	C9—C8—H8B	109.3
C7—C2—C1	121.34 (18)	H8A—C8—H8B	108.0
C3—C2—C1	120.2 (2)	O1—C1—C2	126.2 (2)
C6—C7—C2	123.07 (18)	O1—C1—H1	116.9
C6—C7—H7	118.5	C2—C1—H1	116.9
C2—C7—H7	118.5	C11—C12—C13	110.52 (16)
O2—C3—C4	119.02 (17)	C11—C12—H12A	109.5
O2—C3—C2	120.24 (18)	C13—C12—H12A	109.5
C4—C3—C2	120.7 (2)	C11—C12—H12B	109.5
N1—C10—C9	111.68 (16)	C13—C12—H12B	109.5
N1—C10—H10A	109.3	H12A—C12—H12B	108.1
C9—C10—H10A	109.3	C8—C9—C10	108.80 (19)
N1—C10—H10B	109.3	C8—C9—H9A	109.9
C9—C10—H10B	109.3	C10—C9—H9A	109.9
H10A—C10—H10B	107.9	C8—C9—H9B	109.9
N1—C11—C12	110.87 (16)	C10—C9—H9B	109.9
N1—C11—H11A	109.5	H9A—C9—H9B	108.3
C12—C11—H11A	109.5

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O1	0.82	1.89	2.621 (2)	148
C9—H9A···O2ⁱ	0.97	2.50	3.324 (3)	143
C9—H9B···O1ⁱⁱ	0.97	2.55	3.438 (3)	152
O2—H2···O1	0.82	1.89	2.621 (2)	148
C9—H9A···O2ⁱ	0.97	2.50	3.324 (3)	143
C9—H9B···O1ⁱⁱ	0.97	2.55	3.438 (3)	152

Symmetry codes: (i) x, y+1, z; (ii) −x+1, −y+1, −z+1.

Comparison of selected geometric data for (I) (Å ,° ) from calculated (DFT) and X-ray data top

Bonds	X-ray	B3LYP/6–311G(d,p)
C1—O1	1.231 (3)	1.231
C3—O2	1.345 (3)	1.345
C1—C2	1.431 (3)	1.431
N1—C5	1.381 (2)	1.381
O1—C1—C2	126.2 (2)	126.22
C1—C2—C3	121.34 (18)	120.25
C11—N1—C10	116.83 (15)	116.81

Acknowledgements

The authors are grateful to the Department of Chemistry, Taras Shevchenko National University of Kyiv, 64, Vladimirska Str., Kiev, Ukraine, for financial support, and Dr Pratik Sen and Dr Manabendra Ray for valuable discussions.

References

Becke, A. D. (1993). J. Chem. Phys. 98, 5648–5652. CrossRef CAS Web of Science Google Scholar
Bruker (2003). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Choi, Y. W., Lee, J. J., You, G. R., Lee, S. Y. & Kim, C. (2015). RSC Adv. 5, 86463–86472. Web of Science CrossRef CAS Google Scholar
Faizi, M. S. H., Ahmad, M., Kapshuk, A. A. & Golenya, I. A. (2017). Acta Cryst. E73, 38–40. CrossRef IUCr Journals Google Scholar
Faizi, M. S. H., Ali, A. & Potaskalov, V. A. (2016). Acta Cryst. E72, 1366–1369. Web of Science CSD CrossRef IUCr Journals Google Scholar
Frisch, M. J., Trucks, G. W., Schlegel, H. B., Scuseria, G. E., Robb, M. A., Cheeseman, J. R., et al. (2009). GAUSSIAN09. Gaussian Inc., Wallingford, CT, USA. Google Scholar
Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179. Web of Science CSD CrossRef IUCr Journals Google Scholar
Jo, T. G., Na, Y. J., Lee, J. J., Lee, M. M., Lee, S. Y. & Kim, C. (2015). New J. Chem. 39, 2580–2587. Web of Science CrossRef CAS Google Scholar
Kim, Y. S., Lee, J. J., Choi, Y. W., You, G. R., Nguyen, L., Noh, I. & Kim, C. (2016). Dyes Pigments, 129, 43–53. Web of Science CrossRef CAS Google Scholar
Kim, Y. S., Park, G. J., Lee, J. J., Lee, S. Y., Lee, S. Y. & Kim, C. (2015). RSC Adv. 5, 11229–11239. Web of Science CrossRef CAS Google Scholar
Kirchner, M. T., Bläser, D., Boese, R., Thakur, T. S. & Desiraju, G. R. (2011). Acta Cryst. C67, o387–o390. Web of Science CSD CrossRef IUCr Journals Google Scholar
Lee, K. H., Kim, Y. K. & Yoon, S. S. (2012). Bull. Korean Chem. Soc. 33, 3433–3436. CrossRef CAS Google Scholar
Lee, C., Yang, W. & Parr, R. G. (1988). Phys. Rev. B, 37, 785–789. CrossRef CAS Web of Science Google Scholar
Lee, S. A., You, G. R., Choi, Y. W., Jo, H. Y., Kim, A. R., Noh, I., Kim, S.-J., Kim, Y. & Kim, C. (2014). Dalton Trans. 43, 6650–6659. Web of Science CSD CrossRef CAS PubMed Google Scholar
Liang, M., Yennawar, H. & Maroncelli, M. (2009). Acta Cryst. E65, o1687. Web of Science CSD CrossRef IUCr Journals Google Scholar
Mennucci, B., Cappelli, C., Guido, C. A., Cammi, R. & Tomasi, J. (2009). J. Phys. Chem. A, 113, 3009–3020. Web of Science CrossRef PubMed CAS Google Scholar
Nano, A., Gullo, M. P., Ventura, B., Armaroli, N., Barbieri, A. & Ziessel, R. (2015). Chem. Commun. 51, 3351–3354. Web of Science CrossRef CAS Google Scholar
Nano, A., Ziessel, R., Stachelek, P. & Harriman, A. (2013). Chem. Eur. J. 19, 13528–13537. CrossRef CAS PubMed Google Scholar
Park, G. J., Park, D. Y., Park, K.-M., Kim, Y., Kim, S.-J., Chang, P.-S. & Kim, C. (2014). Tetrahedron, 70, 7429–7438. Web of Science CSD CrossRef CAS Google Scholar
Sheldrick, G. M. (2004). SADABS. University of Göttingen, Germany. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Wang, L., Li, H. & Cao, D. (2013). Sens. Actuators B Chem. 181, 749–755. CrossRef CAS Google Scholar
Wu, W.-B., Wang, M.-L., Ye, H.-Y. & Sun, Y.-M. (2007). Acta Cryst. E63, o4699. CrossRef IUCr Journals Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.