(E)-N-(4-Bromo­phen­yl)-1-(quinolin-2-yl)methanimine

Zamisa, S.J.; Adeleke, A.A.; Omondi, B.; Olatunji, O.S.

doi:10.1107/S2414314626008953

organic compounds

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ISSN: 2414-3146

Volume 11| Part 9| September 2026| x260895

https://doi.org/10.1107/S2414314626008953

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(E)-N-(4-Bromophenyl)-1-(quinolin-2-yl)methanimine

Sizwe J. Zamisa,^a ^* Adesola A. Adeleke,^a,^b Bernard Omondi ^a and Olatunde S. Olatunji ^a

^aSchool of Agriculture and Science, Discipline of Chemistry, University of KwaZulu-Natal, Private Bag X54001, Durban, 4000, South Africa, and ^bDepartment of Chemical Sciences, Olabisi Onabanjo University, Ago-Iwoye, PMB 2001, Nigeria
^*Correspondence e-mail: [email protected]

Edited by M. Bolte, Goethe-Universität Frankfurt, Germany (Received 26 August 2026; accepted 28 August 2026; online 3 September 2026)

The title compound, C₁₆H₁₁BrN₂, is a Schiff base formed through the condensation reaction of 2-quinolinecarboxaldehyde with 4-bromoaniline. The C=N bond length of 1.282 (2) Å is consistent with its double-bond character. The imine linkage adopts the E configuration, as indicated by the N—C—C—N torsion angle of 174.27 (14)°. This value also demonstrates that the quinoline ring and imine group are arranged in an almost coplanar manner. In contrast, the 4-bromophenyl ring is significantly twisted relative to the imine-quinoline plane, as indicated by the C—N—C—C torsion angle of approximately 46.8 (2)°. Intermolecular C—H⋯π interactions between quinolinyl and bromophenyl rings form a three-dimensional supramolecular network in the crystal packing.

Keywords: crystal structure; Schiff base; quinoline; imine; 4-bromophenyl.

CCDC reference: 2583971

Structure description

Schiff base compounds derived from aromatic aldehydes and primary amines constitute an important class of organic ligands that have been extensively investigated owing to their ease of preparation, structural versatility, and broad biological and pharmacological profiles, including antibacterial, antifungal, and anticancer activities (Boulechfar et al., 2023 ; Adeleke et al., 2022 ). Among the various aldehyde building blocks employed, quinolinecarboxaldehyde is of particular interest because it incorporates the quinoline pharmacophore, a privileged scaffold in medicinal chemistry known for its activity against a wide range of pathogens and tumour cell lines (Solomon et al., 2011 ). The resulting quinoline-derived Schiff bases combine the chelating and biological potential of the quinoline unit with the donor flexibility of the imine nitrogen, rendering them attractive precursors for metal-complex synthesis and functional material applications (Sonawane et al., 2023 ).

The asymmetric unit of the title compound consists of a single, neutral molecule of (E)-N-(4-bromophenyl)-1-(quinolin-2-yl)methanimine. The molecule comprises a quinoline ring system connected at its 2-position to a methanimine (–CH=N–) bridge, which in turn links to a 4-bromophenyl ring at the imine nitrogen (Fig. 1). The quinoline ring system and the imine fragment are coplanar, as the torsion angles within the quinoline ring confirm near-perfect planarity of this moiety, and the imine carbon lies in this plane, as reflected by the torsion of −2.9 (2)°. In contrast, the 4-bromophenyl ring is significantly twisted with respect to the quinoline–imine plane, as shown by the torsion angle C10—N2—C11—C12 of 46.8 (2)°. Other intramolecular bond parameters are comparable to closely related quinoline-based Schiff bases reported in the literature (Oladipo et al., 2025 ; Wang et al.. 2017a ,b ; Faizi et al., 2015 ). The crystal packing of the title compound features C–H⋯π interactions between the quinolinyl and bromophenyl rings of neighbouring molecules, forming a three-dimensional supramolecular network. (Table 1, Fig. 2).

Table 1
Hydrogen-bond geometry (Å, °)

Cg1, Cg2 and Cg3 are the centroids of the N1/C5–C9, C1–C6 and C11–C16 rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1⋯Cg3ⁱ	0.95	2.67	3.3703 (16)	131
C4—H4⋯Cg2ⁱⁱ	0.95	2.79	3.4808 (17)	130
C7—H7⋯Cg1ⁱⁱ	0.95	2.85	3.5026 (16)	127
C13—H13⋯Cg3ⁱⁱⁱ	0.95	2.69	3.4042 (16)	132
C16—H16⋯Cg2^iv	0.95	2.70	3.3932 (15)	131
Symmetry codes: (i) ; (ii) $[x, -y+{\script{1\over 2}}, z-{\script{3\over 2}}]$ ; (iii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (iv) .

Figure 1
The molecular structure of the title compound shown with displacement ellipsoids at the 50% probability level.

Figure 2
Representation of the C—H⋯π hydrogen bonds in the crystal structure of the title compound (dashed orange lines).

Synthesis and crystallization

The title compound was synthesized by the condensation reaction of an equimolar amount of 2-quinolinecarboxaldehyde with 4-bromoaniline in methanol, with a catalytic amount of glacial acetic acid. The reaction mixture was refluxed for 6 h at 80°C for 4 h, during which time a yellow precipitate was formed. The solid product was isolated by filtration, washed with cold ethanol, and dried in air (Adeleke et al., 2021 ). Single crystals were obtained by slow evaporation of the concentrated solution of the product in ethanol at room temperature.

Refinement

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

Table 2
Experimental details

Crystal data
Chemical formula	C₁₆H₁₁BrN₂
M_r	311.18
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	15.3817 (4), 13.9338 (4), 6.0050 (2)
β (°)	91.654 (1)
V (Å³)	1286.49 (7)
Z	4
Radiation type	Cu Kα
μ (mm⁻¹)	4.23
Crystal size (mm)	0.42 × 0.33 × 0.05

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.545, 0.753
No. of measured, independent and observed [I > 2σ(I)] reflections	19912, 2346, 2224
R_int	0.040
(sin θ/λ)_max (Å⁻¹)	0.602

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.023, 0.062, 1.05
No. of reflections	2346
No. of parameters	172
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.22, −0.45
Computer programs: APEX2 and SAINT (Bruker, 2009 ), SHELXT2018/2 (Sheldrick, 2015a ), SHELXL2019/3 (Sheldrick, 2015b ) and OLEX2 1.5 (Dolomanov et al., 2009 ).

Structural data

CCDC reference: 2583971

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314626008953/bt4206sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314626008953/bt4206Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314626008953/bt4206Isup3.cml

checkCIF report

Computing details top

(E)-N-(4-Bromophenyl)-1-(quinolin-2-yl)methanimine top

Crystal data top

C₁₆H₁₁BrN₂	F(000) = 624
M_r = 311.18	D_x = 1.607 Mg m⁻³
Monoclinic, P2₁/c	Cu Kα radiation, λ = 1.54178 Å
a = 15.3817 (4) Å	Cell parameters from 9977 reflections
b = 13.9338 (4) Å	θ = 2.9–68.1°
c = 6.0050 (2) Å	µ = 4.23 mm⁻¹
β = 91.654 (1)°	T = 100 K
V = 1286.49 (7) Å³	Plate, colourless
Z = 4	0.42 × 0.33 × 0.05 mm

Data collection top

Bruker APEXII CCD diffractometer	2346 independent reflections
Radiation source: microfocus sealed X-ray tube, Incoatec Iµs	2224 reflections with I > 2σ(I)
Mirror optics monochromator	R_int = 0.040
Detector resolution: 7.9 pixels mm^-1	θ_max = 68.1°, θ_min = 2.9°
φ and ω scans	h = −18→17
Absorption correction: multi-scan (SADABS; Krause et al., 2015) wR2(int) was 0.1018 before and 0.0553 after correction. The ratio of minimum to maximum transmission is 0.7237. The λ/2 correction factor is 0.0015.	k = −16→16
T_min = 0.545, T_max = 0.753	l = −6→7
19912 measured reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.023	H-atom parameters constrained
wR(F²) = 0.062	w = 1/[σ²(F_o²) + (0.0377P)² + 0.4867P] where P = (F_o² + 2F_c²)/3
S = 1.05	(Δ/σ)_max = 0.001
2346 reflections	Δρ_max = 0.22 e Å⁻³
172 parameters	Δρ_min = −0.45 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. Hydrogen atoms were located in a difference map and refined as riding on their parent atom with U(H) = 1.2U_eq(C) and with C—H = 0.95 Å.

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

	x	y	z	U_iso*/U_eq
Br1	0.03190 (2)	0.63813 (2)	1.15570 (3)	0.02712 (9)
N1	0.59463 (8)	0.58283 (8)	0.7717 (2)	0.0175 (3)
N2	0.37000 (9)	0.61932 (9)	0.6575 (2)	0.0185 (3)
C13	0.21335 (10)	0.66459 (10)	1.1058 (3)	0.0187 (3)
H13	0.211684	0.692263	1.250160	0.022*
C7	0.60856 (10)	0.65857 (10)	0.3381 (3)	0.0194 (3)
H7	0.612642	0.682644	0.190800	0.023*
C5	0.68526 (11)	0.64033 (9)	0.4694 (3)	0.0176 (3)
C8	0.52919 (11)	0.64130 (9)	0.4251 (3)	0.0197 (3)
H8	0.477397	0.653464	0.339721	0.024*
C4	0.76976 (11)	0.66208 (11)	0.3979 (3)	0.0204 (3)
H4	0.777239	0.689339	0.254716	0.024*
C1	0.74967 (10)	0.58019 (10)	0.8203 (3)	0.0187 (3)
H1	0.743555	0.551406	0.962403	0.022*
C6	0.67467 (10)	0.60071 (10)	0.6855 (2)	0.0167 (3)
C14	0.13806 (11)	0.62969 (10)	1.0021 (3)	0.0187 (3)
C10	0.44132 (10)	0.59306 (10)	0.7552 (2)	0.0187 (3)
H10	0.440070	0.565713	0.900039	0.022*
C11	0.29350 (10)	0.61891 (10)	0.7815 (3)	0.0173 (3)
C9	0.52518 (9)	0.60476 (11)	0.6458 (2)	0.0172 (3)
C12	0.29111 (10)	0.65845 (10)	0.9953 (3)	0.0183 (3)
H12	0.343228	0.681321	1.065495	0.022*
C16	0.21614 (10)	0.58570 (10)	0.6789 (2)	0.0186 (3)
H16	0.217073	0.560089	0.532372	0.022*
C15	0.13827 (10)	0.58990 (10)	0.7894 (3)	0.0199 (3)
H15	0.086093	0.566078	0.721322	0.024*
C3	0.84113 (11)	0.64401 (10)	0.5343 (3)	0.0217 (3)
H3	0.897616	0.659973	0.486127	0.026*
C2	0.83087 (10)	0.60168 (11)	0.7465 (3)	0.0212 (3)
H2	0.880681	0.588095	0.838352	0.025*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.01970 (13)	0.03373 (14)	0.02817 (13)	−0.00120 (6)	0.00494 (8)	−0.00493 (6)
N1	0.0213 (6)	0.0120 (6)	0.0193 (6)	0.0004 (5)	0.0011 (5)	0.0001 (5)
N2	0.0214 (7)	0.0127 (5)	0.0214 (6)	−0.0001 (5)	0.0009 (5)	−0.0005 (5)
C13	0.0238 (8)	0.0124 (6)	0.0196 (7)	0.0003 (6)	−0.0003 (6)	−0.0003 (6)
C7	0.0270 (8)	0.0133 (6)	0.0180 (7)	0.0010 (6)	0.0005 (6)	0.0003 (6)
C5	0.0239 (8)	0.0103 (7)	0.0187 (8)	−0.0004 (5)	0.0019 (6)	−0.0023 (5)
C8	0.0229 (8)	0.0147 (7)	0.0212 (8)	0.0002 (5)	−0.0024 (6)	0.0000 (5)
C4	0.0268 (8)	0.0136 (6)	0.0211 (8)	−0.0023 (6)	0.0053 (6)	−0.0021 (6)
C1	0.0233 (8)	0.0126 (6)	0.0203 (7)	0.0007 (5)	−0.0001 (6)	−0.0008 (5)
C6	0.0202 (7)	0.0101 (6)	0.0198 (7)	−0.0003 (5)	0.0020 (6)	−0.0017 (5)
C14	0.0184 (8)	0.0154 (7)	0.0224 (8)	0.0017 (5)	0.0037 (6)	0.0013 (6)
C10	0.0224 (8)	0.0130 (7)	0.0207 (7)	0.0002 (5)	0.0011 (6)	0.0004 (6)
C11	0.0208 (8)	0.0107 (6)	0.0204 (7)	0.0018 (5)	0.0002 (6)	0.0028 (6)
C9	0.0199 (8)	0.0109 (7)	0.0208 (8)	−0.0001 (5)	0.0001 (6)	−0.0012 (5)
C12	0.0207 (8)	0.0123 (6)	0.0218 (8)	−0.0005 (6)	−0.0032 (6)	−0.0003 (6)
C16	0.0239 (8)	0.0130 (6)	0.0188 (7)	0.0006 (5)	−0.0007 (6)	−0.0008 (5)
C15	0.0200 (8)	0.0166 (7)	0.0231 (8)	−0.0019 (6)	−0.0027 (6)	−0.0002 (6)
C3	0.0227 (8)	0.0158 (7)	0.0268 (8)	−0.0027 (5)	0.0047 (7)	−0.0042 (6)
C2	0.0200 (8)	0.0162 (7)	0.0271 (8)	0.0010 (6)	−0.0022 (6)	−0.0041 (6)

Geometric parameters (Å, º) top

Br1—C14	1.9021 (16)	C4—C3	1.374 (2)
N1—C6	1.372 (2)	C1—H1	0.9500
N1—C9	1.3264 (19)	C1—C6	1.419 (2)
N2—C10	1.282 (2)	C1—C2	1.370 (2)
N2—C11	1.411 (2)	C14—C15	1.392 (2)
C13—H13	0.9500	C10—H10	0.9500
C13—C14	1.387 (2)	C10—C9	1.474 (2)
C13—C12	1.387 (2)	C11—C12	1.399 (2)
C7—H7	0.9500	C11—C16	1.403 (2)
C7—C5	1.423 (2)	C12—H12	0.9500
C7—C8	1.363 (2)	C16—H16	0.9500
C5—C4	1.413 (2)	C16—C15	1.387 (2)
C5—C6	1.423 (2)	C15—H15	0.9500
C8—H8	0.9500	C3—H3	0.9500
C8—C9	1.423 (2)	C3—C2	1.417 (2)
C4—H4	0.9500	C2—H2	0.9500

C9—N1—C6	117.37 (13)	C15—C14—Br1	119.61 (12)
C10—N2—C11	118.23 (13)	N2—C10—H10	119.6
C14—C13—H13	120.5	N2—C10—C9	120.83 (14)
C14—C13—C12	118.95 (14)	C9—C10—H10	119.6
C12—C13—H13	120.5	C12—C11—N2	121.82 (14)
C5—C7—H7	120.2	C12—C11—C16	119.25 (15)
C8—C7—H7	120.2	C16—C11—N2	118.67 (14)
C8—C7—C5	119.59 (14)	N1—C9—C8	123.88 (14)
C7—C5—C6	117.34 (15)	N1—C9—C10	114.92 (13)
C4—C5—C7	123.26 (15)	C8—C9—C10	121.14 (13)
C4—C5—C6	119.37 (15)	C13—C12—C11	120.61 (14)
C7—C8—H8	120.5	C13—C12—H12	119.7
C7—C8—C9	118.90 (14)	C11—C12—H12	119.7
C9—C8—H8	120.5	C11—C16—H16	119.7
C5—C4—H4	119.8	C15—C16—C11	120.62 (14)
C3—C4—C5	120.37 (15)	C15—C16—H16	119.7
C3—C4—H4	119.8	C14—C15—H15	120.6
C6—C1—H1	119.8	C16—C15—C14	118.72 (14)
C2—C1—H1	119.8	C16—C15—H15	120.6
C2—C1—C6	120.33 (14)	C4—C3—H3	119.8
N1—C6—C5	122.81 (14)	C4—C3—C2	120.30 (16)
N1—C6—C1	118.13 (13)	C2—C3—H3	119.8
C1—C6—C5	119.05 (14)	C1—C2—C3	120.52 (15)
C13—C14—Br1	118.56 (12)	C1—C2—H2	119.7
C13—C14—C15	121.83 (15)	C3—C2—H2	119.7

Br1—C14—C15—C16	179.06 (11)	C6—N1—C9—C8	2.9 (2)
N2—C10—C9—N1	174.27 (14)	C6—N1—C9—C10	−174.18 (12)
N2—C10—C9—C8	−2.9 (2)	C6—C5—C4—C3	0.8 (2)
N2—C11—C12—C13	174.38 (13)	C6—C1—C2—C3	−0.4 (2)
N2—C11—C16—C15	−175.74 (13)	C14—C13—C12—C11	0.9 (2)
C13—C14—C15—C16	−0.3 (2)	C10—N2—C11—C12	46.8 (2)
C7—C5—C4—C3	178.98 (13)	C10—N2—C11—C16	−139.02 (14)
C7—C5—C6—N1	−2.1 (2)	C11—N2—C10—C9	−171.29 (13)
C7—C5—C6—C1	179.09 (13)	C11—C16—C15—C14	1.4 (2)
C7—C8—C9—N1	−2.5 (2)	C9—N1—C6—C5	−0.6 (2)
C7—C8—C9—C10	174.41 (13)	C9—N1—C6—C1	178.28 (13)
C5—C7—C8—C9	−0.3 (2)	C12—C13—C14—Br1	179.79 (11)
C5—C4—C3—C2	1.2 (2)	C12—C13—C14—C15	−0.8 (2)
C8—C7—C5—C4	−175.72 (14)	C12—C11—C16—C15	−1.4 (2)
C8—C7—C5—C6	2.5 (2)	C16—C11—C12—C13	0.3 (2)
C4—C5—C6—N1	176.16 (13)	C2—C1—C6—N1	−176.41 (13)
C4—C5—C6—C1	−2.7 (2)	C2—C1—C6—C5	2.5 (2)
C4—C3—C2—C1	−1.4 (2)

Hydrogen-bond geometry (Å, º) top

Cg1, Cg2 and Cg3 are the centroids of the N1/C5–C9, C1–C6 and C11–C16 rings, respectively.

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···Cg3ⁱ	0.95	2.67	3.3703 (16)	131
C4—H4···Cg2ⁱⁱ	0.95	2.79	3.4808 (17)	130
C7—H7···Cg1ⁱⁱ	0.95	2.85	3.5026 (16)	127
C13—H13···Cg3ⁱⁱⁱ	0.95	2.69	3.4042 (16)	132
C16—H16···Cg2^iv	0.95	2.70	3.3932 (15)	131

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

Acknowledgements

The authors are grateful to the University of KwaZulu-Natal for providing access to X-ray diffraction facilities.

References

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organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

(E)-N-(4-Bromo­phen­yl)-1-(quinolin-2-yl)methanimine

Structure description

Synthesis and crystallization

Refinement

Structural data

Acknowledgements

References

organic compounds

(E)-N-(4-Bromophenyl)-1-(quinolin-2-yl)methanimine