Ethyl 10-cyano-7-hy­droxy-6-oxo-3-phenyl-8,9,10,10a-tetra­hydro-6H-benzo[c]chromene-10-carboxyl­ate

Surya Prakash Rao, H.; M, P.; Muthukumaran, J.

doi:10.1107/S2414314622001997

organic compounds

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ISSN: 2414-3146

Volume 7| Part 2| February 2022| x220199

https://doi.org/10.1107/S2414314622001997

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Ethyl 10-cyano-7-hydroxy-6-oxo-3-phenyl-8,9,10,10a-tetrahydro-6H-benzo[c]chromene-10-carboxylate

H. Surya Prakash Rao,^a,^b ^* Prabakaran M ^a and Jayaraman Muthukumaran ^c

^aDepartment of Chemistry, Pondicherry University, Puducherry 605014, India, ^bVasista Pharma Chem Pvt Ltd, Gajularamaram, Hyderabad 500090, India, and ^cDepartment of Biotechnology, School of Engineering and Technology, Sharda, University, Greater Noida 201306, India
^*Correspondence e-mail: profhspr@gmail.com

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 7 February 2022; accepted 19 February 2022; online 25 February 2022)

In the title compound, C₂₃H₁₉NO₅, the cyano group adopts an axial orientation and the ester group an equatorial orientation. The dihedral angle between the pendant phenyl group and the benzene ring of the fused-ring system is 25.97 (8)°. Intramolecular O—H⋯O and C—H⋯O hydrogen bonds are observed and the packing is consolidated by C—H⋯O and C—H⋯π interactions.

Keywords: dibenzopyran; C—H⋯π interaction; C—H⋯O interaction; crystal structure.

CCDC reference: 2153368

Structure description

Dibenzopyran-6-ones (also called 6H-benzo[c]chromen-6-ones or 3,4,5,6-dibenzo-α-pyranones) form an important group of biologically active natural products that occur in bacteria, fungi, lichens, higher plants and animal waste (Bialonska et al., 2009 ). Elsamitrucin, a dibenzopyran-6-one derived drug, is an efficient topoisomerase II inhibitor (Fiocchi et al., 2011 ). As well as their biological activities, some dibenzopyran-6-ones have served as intermediates in the synthesis of more complex organic compounds (see, for example, Coghlan et al., 2001 ). As a part of our ongoing studies in this area, we now describe the synthesis and crystal structure of the title compound.

The title compound has a dibenzopyran moiety decorated by several substituents, as shown in Fig. 1. There are two stereogenic centres: in the arbitrarily chosen asymmetric molecule, C15 and C20 have S and R configurations, respectively, but crystal symmetry generates a racemic mixture. The nitrile group attached to C20 occupies an axial position and is anti to the hydrogen atom attached to C19. The dihedral angle between the pendant C1–C6 phenyl group and the C7–C12 benzene ring of the fused-ring system is 25.97 (8)°. The Cremer–Pople puckering parameters of the O1/C9/C10/C13–C15 and C14/C15/C17–C20 rings indicate half-chair conformations in each case with puckering amplitudes Q = 0.359 Å; θ = 104.52°; φ = 9.27° and Q = 0.49 Å; θ = 134.17°; φ = 327.35°, respectively. The O atom attached to C17 is stabilized in its enol (hydroxy) form, presumably as a result of forming a strong intramolecular hydrogen bond to O2. The packing is consolidated by weak C—H⋯O hydrogen bonds and C—H⋯π interactions (Table 1) and an intramolecular C—H⋯O interaction is also observed (Fig. 2).

Table 1
Hydrogen-bond geometry (Å, °)

Cg2 and Cg3 are the centroids of the C1–C6 and C7–C12 rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3⋯O2	0.82	1.86	2.5702 (16)	145
C11—H11⋯O4	0.93	2.54	3.399 (2)	154
C18—H18B⋯O1ⁱ	0.97	2.60	3.4289 (19)	144
C19—H19B⋯O2ⁱ	0.97	2.60	3.285 (2)	128
C15—H15⋯Cg2ⁱⁱ	0.98	2.95	3.7685 (17)	142
C23—H23B⋯Cg3ⁱⁱⁱ	0.96	2.82	3.686 (3)	151
Symmetry codes: (i) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (ii) ; (iii) $[-x+{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

Figure 1
The molecular structure of the title compound with the atom-numbering scheme and displacement ellipsoids drawn at the 50% probability level. Intramolecular hydrogen bonds are shown as dashed lines.

Figure 2
Intermolecular interactions in the title compound.

From a Cambridge Structural Database search (Groom et al., 2016 ), we found compounds identified by refcodes OKEYUB (Xiao et al., 2021 ), QABVEY (Wang et al., 2021 ), ALTENU (McPhail et al., 1973 ), AMUYIS (Alzaydi et al., 2016 ), ANOVEG (Sosnovskikh et al., 2016 ), ANOVIK (Sosnovskikh et al., 2016), BUWJEK (Parveen et al., 2015 ), BUXLOW (Fatunsin et al., 2010 ), DIPTUR (Casiraghi et al., 1986 ), DISJAS (Lee et al., 2013 ), SEDFEN (Appel et al., 2006 ), SIVQIZ (Poudel & Lee, 2014 ), SIJZER (Hussain et al., 2007 ), TUPJOE (Siegel et al., 2010 ), ZAQHIK (Dasari et al., 2012 ) and IZACIY (Duan et al., 2021 ) to be similar to the title compound.

Synthesis and crystallization

A mixture of ethyl 10-cyano-7-hydroxy-6-oxo-3-{[(trifluoromethyl)sulfonyl]oxy}-8,9,10,10a-tetrahydro-6H-benzo[c]chromene-10-carboxylate (100 mg, 0.22 mmol), phenylboronic acid (34 mg, 0.28 mmol, 1.3 equiv.), K₃PO₄ (73 mg, 0.34 mmol, 1.6 equiv.) and Pd(PPh₃)₄ (3 mg, 3 mol%) in degassed 1,4-dioxane (10 mL) was stirred at 100° C for 12 h under nitrogen. After completion of the coupling reaction (TLC), the mixture was cooled to room temperature, diluted with dichloromethane (DCM, 10 mL) and decanted. The residue was extracted with DCM (10 mL × 2) twice. The solvent was removed from the combined DCM layers and the residue was subjected to column chromatography on silica gel (100–200 mesh) by using increasing amounts of ethyl acetate in hexane (5% to 15%) as eluent to afford the title compound as a light-yellow solid in 90% yield (84 mg); R_f = 0.4 (hexanes:ethyl acetate, 7:3); m.p. 155–158° C. A sample suitable for single-crystal X-ray analysis was obtained by recrystallization the 50 mg of the solid from a mixture of 1 mL of distilled chloroform and 0.5 mL of distilled methanol.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	C₂₃H₁₉NO₅
M_r	389.39
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	293
a, b, c (Å)	9.7089 (8), 14.3510 (12), 14.2749 (15)
β (°)	106.946 (10)
V (Å³)	1902.6 (3)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.10
Crystal size (mm)	0.75 × 0.44 × 0.42

Data collection
Diffractometer	Xcalibur, Eos
Absorption correction	Multi-scan (CrysAlis PRO; Agilent, 2014 )
T_min, T_max	0.932, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	10689, 4413, 3119
R_int	0.026
(sin θ/λ)_max (Å⁻¹)	0.686

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.046, 0.157, 0.95
No. of reflections	4413
No. of parameters	264
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.19, −0.20
Computer programs: CrysAlis PRO (Agilent, 2014), SHELXT (Sheldrick, 2015a ), SHELXL2018 (Sheldrick, 2015b ), ORTEP-3 for Windows (Farrugia, 2012 ), PLATON (Spek, 2020 ) and Mercury (Macrae et al., 2020 ).

Structural data

CCDC reference: 2153368

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314622001997/hb4401sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314622001997/hb4401Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314622001997/hb4401Isup3.cml

checkCIF report

Computing details top

Data collection: CrysAlis PRO (Agilent, 2014); cell refinement: CrysAlis PRO (Agilent, 2014); data reduction: CrysAlis PRO (Agilent, 2014); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012), PLATON (Spek, 2020) and Mercury (Macrae et al., 2020); software used to prepare material for publication: ORTEP-3 for Windows (Farrugia, 2012), PLATON (Spek, 2020) and Mercury (Macrae et al., 2020).

Ethyl 10-cyano-7-hydroxy-6-oxo-3-phenyl-8,9,10,10a-tetrahydro-6H-benzo[c]chromene-10-carboxylate top

Crystal data top

C₂₃H₁₉NO₅	F(000) = 816
M_r = 389.39	D_x = 1.359 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 9.7089 (8) Å	Cell parameters from 2883 reflections
b = 14.3510 (12) Å	θ = 3.0–29.1°
c = 14.2749 (15) Å	µ = 0.10 mm⁻¹
β = 106.946 (10)°	T = 293 K
V = 1902.6 (3) Å³	Block, colorless
Z = 4	0.75 × 0.44 × 0.42 mm

Data collection top

Xcalibur, Eos diffractometer	4413 independent reflections
Radiation source: Enhance (Mo) X-ray Source	3119 reflections with I > 2σ(I)
Detector resolution: 15.9821 pixels mm^-1	R_int = 0.026
ω scans	θ_max = 29.2°, θ_min = 3.0°
Absorption correction: multi-scan (CrysalisPro; Agilent, 2014)	h = −13→13
T_min = 0.932, T_max = 1.000	k = −18→17
10689 measured reflections	l = −18→18

Refinement top

Refinement on F²	Primary atom site location: iterative
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.046	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.157	H-atom parameters constrained
S = 0.95	w = 1/[σ²(F_o²) + (0.1P)²] where P = (F_o² + 2F_c²)/3
4413 reflections	(Δ/σ)_max = 0.010
264 parameters	Δρ_max = 0.19 e Å⁻³
0 restraints	Δρ_min = −0.20 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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2sigma(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

The hydrogen atoms in title compound were placed in calculated positions, with C—H = 0.93–0.97 A° and refined using a riding model with U_iso(H) = 1.2 U_eq(C) or 1.5U_eq(C-methyl).

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

	x	y	z	U_iso*/U_eq
O1	0.53859 (10)	0.16733 (8)	0.92065 (7)	0.0410 (3)
O2	0.63028 (12)	0.27465 (8)	0.84841 (8)	0.0509 (3)
C14	0.44382 (14)	0.18379 (10)	0.74486 (11)	0.0347 (3)
O5	0.27716 (13)	−0.06937 (8)	0.61784 (10)	0.0595 (4)
C15	0.36436 (14)	0.09212 (10)	0.73953 (10)	0.0332 (3)
H15	0.431514	0.042889	0.734017	0.040*
O3	0.50815 (13)	0.31695 (9)	0.66833 (9)	0.0588 (4)
H3	0.561932	0.325224	0.723781	0.088*
C9	0.42029 (14)	0.11197 (10)	0.92053 (11)	0.0337 (3)
C10	0.32907 (15)	0.07558 (10)	0.83485 (11)	0.0347 (3)
C7	0.29134 (15)	0.04148 (11)	1.02203 (11)	0.0366 (4)
C4	0.27309 (15)	0.02080 (11)	1.11980 (11)	0.0382 (4)
C19	0.28311 (17)	0.11903 (13)	0.55664 (11)	0.0447 (4)
H19A	0.360887	0.079214	0.550748	0.054*
H19B	0.203779	0.112652	0.497179	0.054*
C16	0.11816 (17)	0.14945 (12)	0.65498 (12)	0.0450 (4)
C13	0.54193 (15)	0.21194 (11)	0.83729 (11)	0.0375 (4)
C20	0.23367 (15)	0.08697 (11)	0.64512 (11)	0.0377 (4)
C8	0.40422 (15)	0.09584 (10)	1.01183 (11)	0.0366 (4)
H8	0.469369	0.121527	1.066950	0.044*
C21	0.17320 (17)	−0.01170 (12)	0.62229 (11)	0.0437 (4)
O4	0.05006 (13)	−0.03278 (10)	0.60776 (10)	0.0649 (4)
C12	0.19570 (17)	0.00624 (12)	0.93635 (12)	0.0443 (4)
H12	0.117331	−0.029036	0.940506	0.053*
C18	0.33369 (17)	0.21905 (12)	0.56740 (12)	0.0467 (4)
H18A	0.381800	0.232559	0.518170	0.056*
H18B	0.250752	0.259856	0.555766	0.056*
C17	0.43402 (16)	0.23902 (11)	0.66616 (12)	0.0410 (4)
C11	0.21487 (17)	0.02259 (12)	0.84563 (12)	0.0443 (4)
H11	0.149569	−0.002549	0.790253	0.053*
C6	0.20395 (18)	−0.05906 (13)	1.13558 (13)	0.0507 (4)
H6	0.166517	−0.099657	1.083600	0.061*
C3	0.32765 (18)	0.08032 (12)	1.19927 (12)	0.0466 (4)
H3A	0.375026	0.134713	1.191218	0.056*
C2	0.2424 (2)	−0.02057 (16)	1.30377 (15)	0.0627 (5)
H2	0.231601	−0.034154	1.364935	0.075*
C1	0.1887 (2)	−0.08045 (15)	1.22642 (15)	0.0637 (5)
H1	0.142442	−0.135050	1.235243	0.076*
C5	0.3116 (2)	0.05875 (15)	1.29030 (14)	0.0579 (5)
H5	0.348412	0.098916	1.342756	0.070*
C22	0.2376 (2)	−0.16616 (14)	0.59282 (18)	0.0714 (6)
H22A	0.150569	−0.169084	0.538150	0.086*
H22B	0.220030	−0.197877	0.648226	0.086*
C23	0.3565 (3)	−0.21069 (18)	0.5666 (2)	0.1099 (10)
H23A	0.372605	−0.179133	0.511451	0.165*
H23B	0.333040	−0.274743	0.550071	0.165*
H23C	0.442123	−0.207456	0.621170	0.165*
N1	0.03398 (17)	0.20167 (13)	0.66178 (13)	0.0658 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0360 (5)	0.0501 (7)	0.0321 (6)	−0.0093 (5)	0.0023 (4)	0.0025 (5)
O2	0.0501 (7)	0.0508 (7)	0.0448 (7)	−0.0184 (6)	0.0029 (5)	0.0017 (5)
C14	0.0322 (7)	0.0351 (8)	0.0334 (8)	−0.0002 (6)	0.0042 (6)	0.0018 (6)
O5	0.0520 (7)	0.0435 (7)	0.0799 (10)	−0.0124 (6)	0.0143 (6)	−0.0140 (6)
C15	0.0313 (7)	0.0349 (8)	0.0296 (8)	0.0014 (6)	0.0027 (6)	0.0016 (6)
O3	0.0606 (8)	0.0537 (8)	0.0516 (8)	−0.0181 (6)	−0.0003 (6)	0.0162 (6)
C9	0.0306 (7)	0.0323 (8)	0.0347 (8)	0.0019 (6)	0.0041 (6)	0.0024 (6)
C10	0.0364 (7)	0.0323 (8)	0.0318 (8)	0.0017 (6)	0.0040 (6)	0.0029 (6)
C7	0.0385 (7)	0.0357 (8)	0.0338 (9)	0.0056 (6)	0.0078 (6)	0.0026 (6)
C4	0.0365 (7)	0.0410 (9)	0.0375 (9)	0.0092 (6)	0.0115 (6)	0.0034 (7)
C19	0.0431 (8)	0.0569 (11)	0.0311 (9)	−0.0059 (8)	0.0060 (6)	0.0023 (7)
C16	0.0375 (8)	0.0543 (10)	0.0396 (10)	0.0015 (8)	0.0056 (6)	0.0104 (8)
C13	0.0334 (7)	0.0373 (8)	0.0383 (9)	−0.0003 (6)	0.0051 (6)	0.0039 (7)
C20	0.0341 (7)	0.0448 (9)	0.0307 (8)	−0.0029 (6)	0.0039 (6)	0.0012 (7)
C8	0.0379 (7)	0.0349 (8)	0.0324 (8)	0.0026 (6)	0.0028 (6)	−0.0005 (6)
C21	0.0431 (9)	0.0534 (10)	0.0307 (9)	−0.0102 (8)	0.0049 (6)	−0.0038 (7)
O4	0.0483 (7)	0.0789 (10)	0.0652 (9)	−0.0248 (7)	0.0132 (6)	−0.0154 (7)
C12	0.0437 (8)	0.0481 (10)	0.0389 (9)	−0.0103 (7)	0.0086 (7)	0.0044 (7)
C18	0.0430 (9)	0.0564 (11)	0.0361 (9)	−0.0032 (7)	0.0045 (7)	0.0121 (8)
C17	0.0377 (8)	0.0423 (9)	0.0399 (9)	−0.0027 (7)	0.0064 (6)	0.0052 (7)
C11	0.0444 (8)	0.0481 (10)	0.0344 (9)	−0.0110 (7)	0.0022 (7)	0.0010 (7)
C6	0.0548 (10)	0.0529 (11)	0.0485 (11)	−0.0025 (8)	0.0214 (8)	0.0004 (8)
C3	0.0476 (9)	0.0504 (10)	0.0426 (10)	0.0034 (8)	0.0144 (7)	−0.0021 (8)
C2	0.0683 (12)	0.0819 (15)	0.0468 (12)	0.0071 (11)	0.0307 (10)	0.0081 (10)
C1	0.0711 (12)	0.0699 (14)	0.0602 (13)	−0.0059 (11)	0.0348 (10)	0.0087 (10)
C5	0.0591 (11)	0.0746 (13)	0.0424 (11)	0.0072 (10)	0.0185 (8)	−0.0082 (9)
C22	0.0747 (13)	0.0481 (12)	0.0924 (17)	−0.0228 (10)	0.0258 (11)	−0.0196 (11)
C23	0.100 (2)	0.0564 (15)	0.188 (3)	−0.0203 (13)	0.065 (2)	−0.0405 (17)
N1	0.0558 (9)	0.0742 (11)	0.0700 (12)	0.0198 (9)	0.0222 (8)	0.0222 (9)

Geometric parameters (Å, º) top

O1—C13	1.3599 (18)	C7—C4	1.487 (2)
O1—C9	1.3961 (17)	C4—C6	1.379 (2)
O2—C13	1.2212 (18)	C4—C3	1.395 (2)
C14—C17	1.355 (2)	C19—C18	1.510 (2)
C14—C13	1.442 (2)	C19—C20	1.546 (2)
C14—C15	1.516 (2)	C16—N1	1.134 (2)
O5—C21	1.321 (2)	C16—C20	1.474 (2)
O5—C22	1.457 (2)	C20—C21	1.531 (2)
C15—C10	1.516 (2)	C21—O4	1.1913 (18)
C15—C20	1.5604 (19)	C12—C11	1.381 (2)
O3—C17	1.3255 (19)	C18—C17	1.489 (2)
C9—C8	1.377 (2)	C6—C1	1.382 (2)
C9—C10	1.386 (2)	C3—C5	1.388 (2)
C10—C11	1.390 (2)	C2—C5	1.363 (3)
C7—C8	1.387 (2)	C2—C1	1.376 (3)
C7—C12	1.397 (2)	C22—C23	1.460 (3)

C13—O1—C9	119.76 (11)	O1—C13—C14	119.40 (13)
C17—C14—C13	117.57 (14)	C16—C20—C21	109.13 (13)
C17—C14—C15	123.65 (13)	C16—C20—C19	108.83 (12)
C13—C14—C15	118.68 (13)	C21—C20—C19	107.00 (13)
C21—O5—C22	117.30 (14)	C16—C20—C15	109.78 (13)
C14—C15—C10	109.62 (12)	C21—C20—C15	113.11 (12)
C14—C15—C20	111.00 (12)	C19—C20—C15	108.88 (12)
C10—C15—C20	115.36 (12)	C9—C8—C7	120.33 (13)
C8—C9—C10	123.53 (14)	O4—C21—O5	125.08 (16)
C8—C9—O1	114.50 (12)	O4—C21—C20	125.09 (16)
C10—C9—O1	121.96 (13)	O5—C21—C20	109.79 (13)
C9—C10—C11	115.70 (14)	C11—C12—C7	121.50 (15)
C9—C10—C15	118.66 (13)	C17—C18—C19	112.50 (13)
C11—C10—C15	125.57 (13)	O3—C17—C14	124.59 (14)
C8—C7—C12	117.11 (14)	O3—C17—C18	112.66 (13)
C8—C7—C4	121.65 (13)	C14—C17—C18	122.73 (14)
C12—C7—C4	121.25 (14)	C12—C11—C10	121.79 (14)
C6—C4—C3	117.61 (15)	C4—C6—C1	121.87 (18)
C6—C4—C7	121.05 (15)	C5—C3—C4	120.32 (17)
C3—C4—C7	121.33 (15)	C5—C2—C1	119.68 (18)
C18—C19—C20	111.65 (14)	C2—C1—C6	119.68 (19)
N1—C16—C20	176.08 (18)	C2—C5—C3	120.84 (18)
O2—C13—O1	115.36 (13)	O5—C22—C23	107.97 (17)
O2—C13—C14	125.24 (14)

Hydrogen-bond geometry (Å, º) top

Cg2 and Cg3 are the centroids of the C1–C6 and C7–C12 rings, respectively.

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O2	0.82	1.86	2.5702 (16)	145
C11—H11···O4	0.93	2.54	3.399 (2)	154
C18—H18B···O1ⁱ	0.97	2.60	3.4289 (19)	144
C19—H19B···O2ⁱ	0.97	2.60	3.285 (2)	128
C15—H15···Cg2ⁱⁱ	0.98	2.95	3.7685 (17)	142
C23—H23B···Cg3ⁱⁱⁱ	0.96	2.82	3.686 (3)	151

Symmetry codes: (i) x−1/2, −y+1/2, z−1/2; (ii) −x+1, −y, −z+2; (iii) −x+1/2, y−1/2, −z+3/2.

Acknowledgements

The authors thank the DST–FIST Single Crystal XRD facility at the Department of Chemistry, Pondicherry University, for the diffraction data and Dr Clara Gomes (FCT–UNL, Portugal) for the CSD database survey. MP thanks the Department of Chemistry for facilities. JM thanks Dr Amit Kumar Singh (Sharda University, India) for support.

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