Coumarin-based thiosemicarbazones as potent urease inhibitors: synthesis, solid state self-assembly and molecular docking

Abstract

A series of coumarin-based thiosemicarbazones and their metal complexes have been synthesized and their in vitro potency against urease was evaluated. Single crystal X-ray crystallographic studies were carried out for compound 14 to investigate the solid state self-assembly which showed a preference for the S-conformation owing to intramolecular hydrogen bonding. An in vitro urease inhibition assay revealed coumarin-thiosemicarbazone 12 as the most potent inhibitor (IC₅₀ value of 2.23 ± 0.14 μM) compared to thiourea, used as standard (IC₅₀ value of 21.25 ± 0.15 μM). Similarly, compounds 4, 6, 7, 9, 15 & 16 showed excellent urease inhibition activity with IC₅₀ values ranging from 4.15 ± 0.17 to 16.95 ± 0.12 μM. Furthermore, compounds 3, 8, 11 & 13 also showed good activities (IC₅₀ values ranging from 33.86 ± 0.12 to 43.12 ± 0.19 μM) against this enzyme. However, the metal complexes of these compounds showed low activity against urease. Molecular docking with the most cogent ligand against urease was also performed to assess the putative binding mode of the synthesized compounds. Potent compound 12 can serve as a potential lead for further chemical tuning towards drug candidate development.

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1. Introduction

Enzyme inhibition via small molecules has enormous significance in curing different diseases. Urease is a well-known enzyme for urea hydrolysis to ammonia and carbon dioxide in living organisms. It is found in bacteria, fungi, plants, vertebrates, etc.¹ Urease elevated activity leads to a high concentration of ammonia which increases stomach pH; a tolerable environment for Helicobacter pylori colonization. Gastric and peptic ulcer pathogeneses are associated with Helicobacter pylori activity. Urease can also induce some other complications such as development of kidney stones, pyelonephritis, hepatic coma, etc.² Due to the role of urease in such clinically important complications, it is necessary to regulate urease activity by using inhibitors.^1,3 Several classes of different compounds have been reported as urease inhibitors.⁴ Thiosemicarbazide moiety serves as an important component in several molecules of biological interest.^5–10 A close structural resemblance of thiosemicarbazide with thiourea draws significant attention for urease inhibition as thiourea is usually used as standard in urease inhibitory assays.

In the present study, we have synthesized a series of coumarin-based thiosemicarbazones and their metal (Cu, Ni, Zn, Co) complexes and tested them as urease inhibitors. The reason for inclusion of coumarin moiety in our design was its diverse range of biologically properties^11,12 that includes antimicrobial and antituberculosis,¹³ antihypertensive,¹⁴ hypoglycemic,¹⁵ activities etc. Furthermore, coumarin hybrids have been reported as potential candidates for anti-cancer^16–18 and as therapeutic agents.¹⁹ Therefore, it was thought worthwhile to conjugate coumarin moiety with thiosemicarbazides for better display of urease inhibition activity. A range of substituted phenyl ring thiosemicarbazides were conjugated with coumarin to study the effect of substituents on urease inhibitory activity.

2. Results and discussion

2.1 Chemistry

A synthetic layout of coumarin-based thiosemicarbazones is shown in the Scheme 1.²⁰ 2-[(2-Oxochromen-3-yl)methoxy]benzaldehyde 1 was treated with corresponding N-substituted thiosemicarbazides 2 in ethanol in the presence of p-toluene sulphonic acid as catalyst. The corresponding 2-[(2-oxochromen-3-yl)methoxy]benzaldehyde 3-thiosemicarbazones 3–18 (Scheme 1) were obtained in 87–95% yield. The structures of all the synthesized compounds were confirmed by means of their microanalysis (CHN) and spectral data i.e. IR, NMR, HREI-MS. The IR spectra of 3–18 showed absorption bands of NH stretching in the range of 3354–3200 and 3196–3055 cm⁻¹. The absorption bands of azomethine C=N and thioamide C=S stretchings appeared in the range of 1629–1564 and 1182–1143 cm⁻¹ regions, respectively. The ¹H-NMR spectra of 3–18 displayed three separate singlets at δ 9.93–12.08, δ 9.09–10.17 and δ 7.91–8.21 attributed to N–H, CS–NH and CH–C=N respectively for the targeted thiosemicarbazones. Furthermore, four compounds of the series 8, 11, 14 and 15 were unambiguously characterized by X-ray single crystal analysis to confirm the assigned structures and to establish conformations of the synthesized thiosemicarbazones; out of which three compounds 8, 11 and 15 are previously reported.²⁰

Scheme 1 The synthetic route to the title compounds 3–18.

The metal (Cu, Ni, Zn and Co) complexes 19–52 of the coumarin-based thiosemicarbazones 3–18 were prepared by the reaction of metal(II) chloride/acetate with the ligands in of 1 : 2 molar ratio. The preparation procedure and the characterization details of metal complexes 19–52 are provided in the ESI.†

2.2 Crystal structure/solid state self-assembly of 14

The good quality single crystals of compound 14 (Table S1†) suitable for X-ray analysis were grown by slow evaporation of its solution in 1,4-dioxane solvent. The compound 14 was crystallized as 1,4-dioxane solvate and was found to have triclinic crystal lattice with the P1̄ space group. The molecular structure (ORTEP diagram) of compound 14 along with crystallographic numbering scheme is presented in Fig. 1. In the crystal structure, the central N-iminothiourea moiety is nearly planar and present in S-trans and S-cis conformation.^20,21 The dihedral angles between S(1)–C(18)–N(2)–H(2A) and S(1)–C(18)–N(3)–H(3A) are −5.57° and −175.69°, respectively. The reason of this planarity can be attributed to the significant delocalization of lone pair of electrons of nitrogens onto the thiocarbonyl, which is clearly evidenced by the shorter N–C bond lengths [N(2)–C(18) 1.350(19) Å and N(3)–C(18) 1.336(2) Å], and hence the partial double bond character of N–C bonds. The slightly longer bond length in one of the N–C bond which is directly connected to the imino moiety (–N=C–) indicates less delocalization of nitrogen lone pair towards thiocarbonyl, most probably due to the attachment of sp²-hybridized nitrogen atom. This planarity may result into two different conformations of thiourea moiety; one in which both the hydrogens are trans to the sulfur (S-trans, S-trans conformation) and the other in which a hydrogen is present on both sides of the sulfur (S-trans, S-cis conformation). However, due to the presence of additional imino moiety in thiosemicarbazones and its apparent ability of making intramolecular hydrogen bond with the NH-protons [N(1)–H(3A)⋯N(1) 2.216 Å] provides preferably S-trans and S-cis conformation. An expected consequence of this conformational preference is the facile formation of a centrosymmetric thioamide dimer R₂²(8) {⋯H–N–C=S}₂ synthon; the key interactions involved in the molecular packing of compound 14.

Fig. 1 The molecular structure (ORTEP diagram) of compound 14. Note: the 1,4-dioxane molecule in the unit cell has been omitted for clarity.

The compound 14 was self-assemble in layers which are composed of various 1D-tapes (Fig. 2). Other than centrosymmetric thioamide R₂²(8) dimer synthon [N(2)–H(2A)⋯S(1) 2.571 Å], the tape consists of R₂²(26) [N(3)–H(3A)⋯O(2) 2.225 Å] motif, resulted due to the interactions of thioamide S-trans hydrogens with the carbonyl oxygen of the coumarin (Fig. 2a). Each tape is further connected with the neighboring tapes by means of centrosymmetric CH⋯O^22,23 [C(2)–H(2)⋯O(1) 2.689 Å] interactions to form a layer (Fig. 2b). It is interesting to mention here that 1,4-dioxane molecules are playing key role in connecting the two consecutive layers by means of CH⋯π [C(26)–H(26B)⋯C(3) 2.799 Å, C(28)–H(28A)⋯C(23) 2.897 Å], CH⋯O [C(20)–H(20)⋯O(4) 2.666 Å] and lone pair-π [O(5)⋯C(9) 3.024 Å] interactions.^22–24 Furthermore, the CH⋯π [C(13)–H(13)⋯C(23) 2.785 Å, C(13)-H(13)⋯C(24) 2.791 Å] interactions^22–24 involving two molecules of 14 of two consecutive layers are also observed, providing an overall multilayered 3D-network (Fig. 2c and d).

Fig. 2 Molecular packing of compound 14: (a) 1D-tapes viewed along a-axis, (b) view of two consecutive tapes of a layer along a-axis that are connected through centrosymmetric CH⋯O interactions, (c) two consecutive layers viewed along a-axis, (d) two consecutive layers having 1,4-dioxane molecules in the crystal lattice viewed along c-axis. The 1,4-dioxane molecules from (a), (b), and (c) are removed for clarity.

2.3 In vitro urease inhibition

All the synthesized thiosemicarbazones 3–18 and their metal (Cu, Ni, Zn and Co) complexes 19–52 were screened for urease inhibition activity.^9,25 In the bioactivity assay thiourea served as reference inhibitor with IC₅₀ value of 21.25 ± 0.15 μM. The results shown in Table 1 demonstrated that the introduction of one or two substituents on the phenyl ring at N³ of the thiosemicarbazone moiety either led to reduction or enhancement of enzymatic activity when compared to 2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)-N-phenylhydrazine-1-carbothioamide 3 (IC₅₀ value of 41.25 ± 0.17 μM) having no substituent. For example, compound 13 bearing two fluoro substituents at position 2′ and 4′ of the phenyl ring displayed slightly decreased activity (IC₅₀ value 43.12 ± 0.19 μM) compared to the compound 3 having no fluoro substituents. Similarly, compound 8 bearing a methoxy substituent at 3′ position of phenyl ring displayed activity (IC₅₀ value 41.87 ± 0.12 μM) which is also comparable to compound 3. However, the other compounds of series 4, 6, 7, 9, 12, 15, and 16 showed a very promising urease inhibition activity. Among these, compound 12 (IC₅₀ value 2.23 ± 0.14 μM) with two chloro substituents at 2′ and 5′ position of phenyl ring was found to be the most active compound of the series. This exceptional activity may be attributed to the strong electron withdrawing effect of the two chloro substituents. It is interesting to mention here that the compound 11, which is also a dichloro substituted compound but with position 2′ and 4′, displayed a much lower activity (IC₅₀ value 33.86 ± 0.12 μM). The change of position of chloro substituents infact played major role in the big difference of activities and IC₅₀ values. The compound 4 with bromo substituent at 2′ position and compound 6 with fluoro substituent at 4′ position of phenyl ring showed excellent activities with IC₅₀ values, 8.38 ± 0.14 μM and 4.93 ± 0.11 μM, respectively. Compounds 7, 8, 9 having methoxy substituent in common but at different positions 2′, 3′ and 4′, respectively exhibited a great diversity in urease inhibition. For example, the compound 7 with methoxy substitution at 2′ position showed good activity (IC₅₀ value 16.95 ± 0.12 μM), compound 8 (IC₅₀ value 41.87 ± 0.19 μM) with methoxy substitution at 3′ position showed poorer inhibition of the urease enzyme relative to that of the control compound, thiourea and compound 9 having methoxy substitution at 4′ position showed excellent activity (IC₅₀ value 7.98 ± 0.12 μM) when compared to other compounds of the series and the control. Similar is the case with compounds 14, 15 and 16 with methyl substitutions at 2′, 3′ and 4′ positions of the phenyl ring, respectively. The compound 14 showed <50% inhibition and was considered as inactive, therefore its IC₅₀ was not measured. However, the compound 15 showed excellent activity with IC₅₀ values 4.15 ± 0.17 μM. The change of methyl position from 3′ to 4′ in compound 16 (IC₅₀ value 15.8 ± 0.19 μM) led to a considerable decrease in activity. These results indicate that the inhibition properties of these compounds are not dependent on the electron releasing or attracting properties of substituent at the phenyl ring. The change in activity in compounds 3–18 with the change in the nature and position of the substituents may be due to their different interactions with the neighboring molecules in the solution state self-assembly or to the binding pockets of the enzyme. Overall, the excellent activity of majority of the compounds compared to the standard, thiourea (Table 1) shows potential of this class of compounds as urease inhibitors. Therefore, these compounds may be used as potent soil ureases inhibitors by mixing with fertilizers in small quantities. Interestingly, most of the metal complexes were found inactive (Table 2). Only the Cu-complex 26 and Co-complex 49 showed activities with IC₅₀ values 19.36 ± 0.26 μM and 116.12 ± 0.09 μM, respectively (Table 2).

Table 1 In vitro urease inhibitory activities of ligands (3–18)^a,b,c

Compounds		Urease	Compounds		Urease
R/R^1		IC50 ± SEM (μM)	R/R^1		IC50 ± SEM (μM)
a IC50 = half maximal inhibitory concentration.b SEM = standard mean error, Std. = standard.c N.A. = not active (compounds having <50% inhibition value considered as not active).
3	Ph	41.25 ± 0.17	11	2′,4'-diCl	33.86 ± 0.12
4	2′-Br	8.38 ± 0.14	12	2′,5'-diCl	2.23 ± 0.14
5	2′-F	N.A.	13	2′,4'-diF	43.12 ± 0.19
6	4′-F	4.93 ± 0.11	14	2′-Me	N.A.
7	2′-OMe	16.95 ± 0.12	15	3′-Me	4.15 ± 0.17
8	3′-OMe	41.87 ± 0.19	16	4′-Me	15.8 ± 0.19
9	4′-OMe	7.98 ± 0.12	17	Benzyl	N.A.
10	3′-Cl	N.A.	18	4′-OCF3	N.A.
Std.	Thiourea	21.25 ± 0.15

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Table 2 In vitro urease inhibition activity of metal(II) complexes^a,b,c (19–52)

Compounds		M	Urease	Compounds		M	Urease
R/R^1			IC50 ± SEM (μM)	R/R^1			IC50 ± SEM (μM)
a IC50 = half maximal inhibitory concentration.b SEM = standard mean error; M = metals.c N.A. = not active (compounds having <50% inhibition value considered as not active).
19	Ph	Cu	—	36	2′,5′-diCl	Ni	N.A.
20	2′-F	Cu	—	37	2′,4′-diF	Ni	—
21	2′-OCH3	Cu	—	38	2′-Br	Zn	—
22	3′-OCH3	Cu	—	39	2′-F	Zn	—
23	4′-OCH3	Cu	—	40	4′-F	Zn	—
24	3-Cl	Cu	—	41	2′-OCH3	Zn	—
25	2′,4′-diCl	Cu	—	42	3′-OCH3	Zn	N.A.
26	2′,5′-diCl	Cu	19.36 ± 0.26	43	4′-OCH3	Zn	N.A.
27	2′,4′-diF	Cu	—	44	3′-Cl	Zn	N.A.
28	2′-Br	Ni	—	45	2′,4′-diCl	Zn	N.A.
29	2′-F	Ni	—	46	2′,5′-diCl	Zn	—
30	4′-F	Ni	—	47	4′-F	Co	N.A.
31	2′-OCH3	Ni	—	48	3′-OCH3	Co	N.A.
32	3′-OCH3	Ni	—	49	4′-OCH3	Co	116.12 ± 0.09
33	4′-OCH3	Ni	—	50	3′-Cl	Co	—
34	3′-Cl	Ni	—	51	2′,4′-diCl	Co	N.A.
35	2′,4′-diCl	Ni	—	52	2′,5′-diCl	Co	—
Thiourea		21.25 ± 0.15

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2.4 Molecular docking simulations for identification of plausible binding mode

In order to identify the plausible binding modes of the synthesized coumarine based thiosemicarbazones compounds in urease, we docked the most active compound 12 in the X-ray crystal structure of bacillus pasteurii urease as shown in Fig. 3. The compound gorged well in the binding site of the protein with high Fred Guasschem Score (−6.660). Further, the cation-π interaction was observed between the phenyl ring of coumarin moiety and one of the nickel atom in the active site of the urease enzyme. We believe that this interaction may be one of the reasons of these compounds to show biological activities against this enzyme. Similarly phenyl ring attached to thiosemicarbazone moiety is positioned towards solvent exposed side which might be responsible for pushing the inhibitors inside the binding pocket of the enzyme.

Fig. 3 Plausible binding mode of the most active compound 12 in urease active site.

3. Conclusions

In summary, a series of coumarin-based thiosemicarbazone ligands 3–18 and their metal complexes 19–52 have been synthesized and evaluated for urease inhibition. The synthesized compounds were characterized through spectroscopic analysis and X-ray diffraction technique was used to determine the solid state self-assembly of compound 14. In urease inhibition assay, coumarin-based thiosemicarbazone 12 with IC₅₀ value of 2.23 ± 0.14 μM was found to be the most active compound in the series. Compounds 6 and 15 were also found to be highly potent antiurease molecules with IC₅₀ values of 4.93 ± 0.11 and 4.15 ± 0.17 μM, respectively. The other compounds of the series showed good to moderate antiurease potential. However, most of the metal complexes were found inactive in this assay. The molecular docking study of compound 12 explored the putative binding modes of these compounds in the enzyme pocket. The highly active compounds i.e. 6, 12 and 15 against urease could be further modified to serve as potential lead candidates.

4. Experimental

4.1 General information

Melting points were taken on a Fisher–Johns melting point apparatus and are uncorrected. Elemental analyses were performed on a Leco CHNS-9320 (USA) elemental analyzer. Infrared spectra (KBr discs) were run on Shimadzu Prestige-21 FT-IR spectrometer. The ¹H-NMR spectra were recorded in CDCl₃ or DMSO-d⁶ on Bruker-500 MHz spectrometer, operating at 500 MHz and at 125 MHz for ¹³C-NMR using TMS as an internal standard. ¹H chemical shifts are reported in δ/ppm and coupling constants in Hz. The electron impact mass spectra (EIMS) were determined with JEOL MS Route mass spectrometer. The progress of the reaction and purity of the products were checked on TLC plates coated with Merck silica gel 60 GF254, and the spots were visualized under ultraviolet light at 254/366 nm and/or spraying with iodine vapours. In vitro biological evaluation of the synthesized compounds was done at Department of Biochemistry and Biotechnology, The Islamia University of Bahawalpur, Bahawalpur.

4.2 Synthesis of coumarin-thiosemicarbazones (3–18)²⁰

A solution of the corresponding thiosemicarbazide (2) (1 mmol, 0.178 g) in ethanol (10 ml) was added dropwise to a stirred hot solution of 2-[(2-oxochromen-3-yl)methoxy]benzaldehyde (1) (1 mmol, 0.2 g) in ethanol (10 mL). p-Toluene sulfonic acid was added as catalyst (0.1% by weight) and the reaction mixture was heated at reflux for 2 h and upon cooling to room temperature, whitish yellow crystalline solids separated. The products were filtered, washed several times with cold ethanol and dried under vacuum. The synthesized compounds were further recrystallized using dioxin as solvent. Spectral data of the thiosemicarbazone ligands (3–18) is provided below. Data of metal complexes is given in the ESI.†

4.3 2-({2-[(2-Oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)-N-phenylhydrazine-1-carbothioamide (3)

Yield, 95%; mp, 152 °C; IR (KBr), ν (cm⁻¹): 3676, 3100, 2933 (NH), 1531 (C=N), 1176 (C=S). ¹H-NMR (CDCl₃), δ (ppm): 5.08 (s, 2H, H-9, CH₂O), 7.04–7.08 (m, 2H, H-3′, 5′), 7.16 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.27–7.30 (m, 3H, H-12, 2′, 6′, Ar-H), 7.37 (d, 1H-8, J = 8.0 Hz, Ar-H), 7.42 (ddd, 1H-13, J = 1.5 Hz, 7.0 Hz, Ar-H), 7.54 (ddd, 1H-14, J = 1.5 Hz, 7.0 Hz, Ar-H), 7.60–7.65 (m, 3H, H-7, 5, 4′, Ar-H), 7.91 (s, 1H, H-17, CH=N), 7.94 (dd, 1H, H-15, J = 1.0 Hz, 8.0 Hz, Ar-H), 8.50 (s, 1H, H-4, CH=C), 9.22 (s, 1H, H-21, NH–CS), 9.93 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 65.21, 112.74, 116.61, 118.84, 121.85, 121.93, 123.91, 124.38, 124.77, 126.17, 126.51, 128.43, 128.75, 131.78, 132.33, 137.78, 138.81, 139.32, 153.24, 156.94, 160.27, 175.73; HRMS calc. for C₂₄H₁₉N₃O₃S 429.1147, found 429.1145. Anal. calcd for C₂₄H₁₉N₃O₃S: C, 67.12; H, 4.46; N, 9.78. Found: C, 67.19; H, 4.57; N, 9.81.

4.4 N-(2-Bromophenyl)-2-({2-[(2-oxo-2H-1-benzopyran-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (4)

Yield, 95%; mp, 157 °C; IR (KBr), ν (cm⁻¹): 3577, 3214, 2933 (NH), 1531 (C=N), 1197 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 5.06 (s, 2H, H-9, CH₂O), 7.06 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.21–7.24 (m, 2H, H-16, 5′, Ar-H), 7.40–7.48 (m, 4H, H-8, 14, 15, 3′ Ar-H), 7.65–7.67 (m, 1H, H-6′, Ar-H), 7.69 (ddd, 1H, H-7, J = 1.5 Hz, 8.0 Hz, Ar-H), 7.75 (dd, 1H, H-4′, J = 1.5 Hz, 8.0 Hz, Ar-H), 7.83 (dd, 1H, H-5, J = 1.5 Hz, 7.5 Hz, Ar-H), 8.21 (s, 1H, H-17, CH=N), 8.24 (dd, 1H, H-13, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.68 (s, 1H, H-4, CH=C), 10.08 (s, 1H, H-21, NH–CS), 11.95 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 65.76, 113.61, 116.67, 119.25, 121.76, 121.82, 122.87, 124.45, 125.25, 126.81, 128.18, 128.41, 129.07, 130.03, 132.19, 132.40, 132.87, 138.35, 139.15, 140.31, 153.33, 157.23, 159.92, 176.71; HRMS calc. for C₂₄H₁₈BrN₃O₃S 507.0252, found 507.0258. Anal. calcd for C₂₄H₁₈BrN₃O₃S: C, 56.70; H, 3.57; N, 8.27. Found: C, 56.61; H, 3.70; N, 8.29.

4.5 N-(2-Fluorophenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (5)

Yield, 95%; mp, 152 °C; IR (KBr), ν (cm⁻¹): 3676, 3100, 2933 (NH), 1531 (C=N), 1176 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 5.06 (s, 2H, H-9, CH₂O), 7.04 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.20–7.23 (m, 2H, H-8, 14, Ar-H), 7.26–7.35 (m, 2H, H-13, 15, Ar-H), 7.41–7.45 (m, 2H, H-3′, 5′, Ar-H), 7.48 (d, 1H, H-6′, J = 8.5 Hz, Ar-H), 7.53 (ddd, 1H, H-4′, J = 1.5 Hz, 8.0 Hz, Ar-H), 7.66 (ddd, 1H, H-7, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.83 (dd, 1H, H-5, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.21 (s, 1H, H-17, CH=N), 8.28 (dd, 1H, H-13, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.67 (s, 1H, H-4, CH=C), 9.98 (s, 1H, H-21, NH–CS), 11.92 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 65.73, 113.59, 116.05, 116.21, 116.68, 119.25, 121.70, 122.89, 124.43, 124.49, 125.26, 126.92, 128.55, 128.61, 129.08, 130.69, 132.15, 132.41, 139.18, 140.30, 153.33, 157.19, 159.93, 177.55; HRMS calc. for C₂₄H₁₈FN₃O₃S 447.1053, found 447.1058. Anal. calcd for C₂₄H₁₈FN₃O₃S: C, 64.42; H, 4.05; N, 9.39. Found: C, 64.65; H, 4.08; N, 9.52.

4.6 N-(4-Fluorophenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (6)

Yield, 95%; mp, 152 °C; IR (KBr), ν (cm⁻¹): 3676, 3100, 2933 (NH), 1531 (C=N), 1176 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 5.05 (s, 2H, H-9, CH₂O), 7.05 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.18–7.23 (m, 3H, H-8, 13, 14, Ar-H), 7.41–7.45 (m, 2H, H-3′, 5′, Ar-H), 7.48 (d, 1H, H-6′, J = 8.5 Hz, Ar-H), 7.54–7.57 (m, 2H, H-4′, 15, Ar-H), 7.67 (ddd, 1H, H-7, J = 1.5 Hz, 7.5 Hz, Ar-H), 7.82 (dd, 1H, H-5, J = 1.5 Hz, 7.5 Hz, Ar-H), 8.21 (s, 1H, H-17, CH=N), 8.33 (dd, 1H, H-13, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.68 (s, 1H, H-4, CH=C), 10.12 (s, 1H, H-21, NH–CS), 11.81 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 65.73, 113.53, 115.05, 115.23, 116.67, 119.25, 121.67, 122.9, 124.47, 125.26, 127.07, 128.55, 129.07, 132.12, 132.4, 135.9, 139.12, 140.32, 153.33, 157.17, 159.15, 159.93, 161.07, 176.62; HRMS calc. for C₂₄H₁₈FN₃O₃S 447.1053, found 447.1056. Anal. calcd for C₂₄H₁₈FN₃O₃S: C, 64.42; H, 4.05; N, 9.39. Found: C, 64.57; H, 4.07; N, 9.48.

4.7 N-(2-Methoxyphenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (7)

Yield, 85%; mp, 177 °C; IR (KBr), ν (cm⁻¹): 3585, 3261, 2933 (NH), 1535 (C=N), 1189 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 3.88 (s, 3H, OCH₃), 5.06 (s, 2H, H-9, CH₂O), 6.96 (ddd, 1H, H-5′, J = 1.0 Hz, 7.5 Hz, Ar-H), 7.09–7.12 (m, 2H, H-6, 8, Ar-H), 7.18 (ddd, 1H, H-4′, J = 1.5 Hz, 8.0 Hz, Ar-H), 7.24 (d, 1H, H-15, J = 8.0 Hz, Ar-H), 7.40–7.48 (m, 3H, H-14, 3′, 6′), 7.65 (ddd, 1H, H-7, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.81 (dd, 1H, H-13, J = 1.5 Hz, 7.5 Hz, Ar-H), 8.08 (dd, 1H, H-5, J = 1.5 Hz, 7.5 Hz, Ar-H), 8.20 (s, 1H, H-17, CH=N), 8.26 (dd, 1H, H-13, J = 1.5 Hz, 7.5 Hz, Ar-H), 8.67 (s, 1H, H-4, CH=C), 10.00 (s, 1H, H-21, NH–CS), 11.89 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 56.43, 65.78, 111.71, 113.78, 116.66, 119.24, 120.34, 121.96, 122.84, 124.33, 124.42, 125.24, 126.16, 128.25, 129.06, 132.22, 132.40, 138.73, 140.34, 151.84, 153.33, 157.25, 159.92, 175.28; HRMS calc. for C₂₅H₂₁N₃O₄S 459.1253, found 459.1257. Anal. calcd for C₂₅H₂₁N₃O₄S: C, 65.34; H, 4.61; N, 9.14. Found: C, 65.26; H, 4.68; N, 9.15.

4.8 N-(3-Methoxyphenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (8)²⁰

Yield, 94%; mp, 168 °C; IR (KBr), ν (cm⁻¹): 3676, 3221, 2933 (NH), 1531 (C=N), 1176 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 3.76 (s, 3H, OCH₃), 5.05 (s, 2H, H-9, CH₂O), 6.77 (m, 1H, H-5′, Ar-H), 7.05 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.19–7.30 (m, 4H, H-5, 8, 15, 4′, Ar-H), 7.41–7.44 (m, 2H, H-14, 6′, Ar-H), 7.66 (ddd, 1H, H-7, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.82 (dd, 1H, H-13, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.21 (s, 1H, H-17, CH=N), 8.32 (dd, 1H, H-13, J = 1.5 Hz, 7.5 Hz, Ar-H), 8.68 (s, 1H, H-4, CH=C), 10.05 (s, 1H, H-21, NH–CS), 11.80 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 55.63, 65.74, 111.20, 111.66, 113.53, 116.68, 118.20, 119.25, 121.71, 122.88, 124.47, 125.26, 127.10, 129.08, 129.18, 132.14, 132.41, 139.10, 140.34, 140.64, 153.34, 157.19, 159.46, 159.94, 175.96; HRMS calc. for C₂₅H₂₁N₃O₄S 459.1253, found 459.1250. Anal. calcd for C₂₅H₂₁N₃O₄S: C, 65.34; H, 4.61; N, 9.14. Found: C, 65.36; H, 4.77; N, no>9.39.

4.9 N-(4-Methoxyphenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (9)

Yield, 91%; mp, 192 °C; IR (KBr), ν (cm⁻¹): 3550, 3264, 2933 (NH), 1535 (C=N), 1201 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 3.77 (s, 3H, OCH₃), 5.05 (s, 2H, H-9, CH₂O), 6.91–6.93 (m, 2H, 3′, 5′, Ar-H), 7.04 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.21 (d, 1H, H-5, J = 8.5 Hz, Ar-H), 7.39–7.44 (m, 4H, H-14, 15, 2′, 6′, Ar-H), 7.47 (d, 1H, H-8, J = 8.5 Hz, Ar-H), 7.65 (ddd, 1H, H-7, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.83 (dd, 1H, H-12, J = 1.0 Hz, 7.5 Hz, Ar-H), 8.21 (s, 1H, H-17, CH=N), 8.32 (dd, 1H, H-13, J = 1.0 Hz, 7.5 Hz, Ar-H), 8.66 (s, 1H, H-4, CH=C), 10.01 (s, 1H, H-21, NH–CS), 11.70 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 55.70, 65.71, 113.51, 113.70, 116.68, 119.26, 121.68, 123.00, 124.50, 125.26, 127.06, 128.02, 129.07, 132.00, 132.40, 132.45, 138.73, 140.27, 153.33, 157.11, 157.39, 159.93, 176.64; HRMS calc. for C₂₅H₂₁N₃O₄S 459.1253, found 459.1256. Anal. calcd for C₂₅H₂₁N₃O₄S: C, 65.34; H, 4.61; N, 9.14. Found: C, 65.55; H, 4.90; N, 9.22.

4.10 N-(3-Chlorophenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (10)

Yield, 88%; mp, 222 °C; IR (KBr), ν (cm⁻¹): 3515, 3270, 2933 (NH), 1533 (C=N), 1208 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 5.06 (s, 2H, H-9, CH₂O), 7.06 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.23–7.27 (m, 2H, H-16, 5′, Ar-H), 7.37–7.48 (m, 4H, H-8, 14, 15, 2′ Ar-H), 7.61 (dd, 1H, H-6′, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.66 (ddd, 1H, H-7, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.76 (t, 1H, H-4′, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.83 (dd, 1H, H-5, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.21 (s, 1H, H-17, CH=N), 8.31 (dd, 1H, H-13, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.69 (s, 1H, H-4, CH=C), 10.17 (s, 1H, H-21, NH–CS), 11.91 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 65.77, 113.56, 116.68, 119.24, 121.70, 122.77, 124.44, 124.61, 125.27, 125.40, 125.58, 127.12, 129.08, 130.04, 132.28, 132.43, 132.59, 139.56, 140.43, 141.03, 153.34, 157.26, 159.95, 176.05; HRMS calc. for C₂₄H₁₈ClN₃O₃S 463.0757, found 463.0760. Anal. calcd for C₂₄H₁₈ClN₃O₃S: C, 62.13; H, 3.91; N, 9.06. Found: C, 62.14; H, 3.96; N, 9.11.

4.11 N-(2,4-Dichlorophenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (11)²⁰

Yield, 93%; mp, 191 °C; IR (KBr), ν (cm⁻¹): 3576, 3264, 2933 (NH), 1531 (C=N), 1201 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 5.06 (s, 2H, H-9, CH₂O), 7.06 (t, 1H, H-6, J = 8.0 Hz, Ar-H), 7.22 (d, 1H, H-16, J = 8.0 Hz, Ar-H), 7.41–7.48 (m, 4H, H-8, 14, 15, 3′ Ar-H), 7.65 (ddd, 1H, H-7, J = 1.5 Hz, 8.0 Hz, Ar-H), 7.71–7.73 (m, 2H, H-5′, 6′, Ar-H), 7.82 (dd, 1H, H-5, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.20 (s, 1H, H-17, CH=N), 8.24 (dd, 1H, H-13, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.68 (s, 1H, H-4, CH=C), 10.08 (s, 1H, H-21, NH–CS), 12.02 (s, 1H, H-19, NH–N); ¹³C NMR δ(ppm) 65.77, 113.64, 116.66, 119.23, 121.77, 122.80, 124.44, 125.25, 126.85, 127.76, 129.07, 129.23, 131.59, 131.65, 132.26, 132.33, 132.40, 136.36, 139.47, 140.37, 153.33, 157.26, 159.92, 176.97; HRMS calc. for C₂₄H₁₇Cl₂N₃O₃S 497.0368, found 497.0371. Anal. calcd for C₂₄H₁₇Cl₂N₃O₃S: C, 57.84; H, 3.44; N, 8.43. Found: C, 57.82; H, 3.45; N, 8.47.

4.12 N-(2,5-Dichlorophenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (12)

Yield, 92%; mp, 197 °C; IR (KBr), ν (cm⁻¹): 3575, 3263, 2936 (NH), 1531 (C=N), 1204 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 5.06 (s, 2H, H-9, CH₂O), 7.06 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.24 (d, 1H, H-16, J = 8.5 Hz, Ar-H), 7.37–7.48 (m, 4H, H-8, 14, 15, 6′ Ar-H), 7.60 (d, 1H, H-4′, J = 8.0 Hz, Ar-H), 7.65 (ddd, 1H, H-7, J = 1.5 Hz, 7.5 Hz, Ar-H), 7.92–7.93 (m, 1H, H-3′, Ar-H), 8.19–8.21 (m, 2H, H-13, 17, Ar-H), 7.82 (dd, 1H, H-5, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.68 (s, 1H, H-4, CH=C), 10.13 (s, 1H, H-21, NH–CS), 12.08 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 65.80, 113.70, 116.67, 119.24, 121.80, 122.73, 124.43, 125.26, 126.77, 127.87, 129.08, 129.30, 129.65, 131.06, 131.45, 132.36, 132.43, 138.25, 139.65, 140.41, 153.34, 157.31, 159.93, 176.61; HRMS calc. for C₂₄H₁₇Cl₂N₃O₃S 497.0368, found 497.0370. Anal. calcd for C₂₄H₁₇Cl₂N₃O₃S: C, 57.84; H, 3.44; N, 8.43. Found: C, 57.93; H, 3.44; N, 8.67.

4.13 N-(2,4-Difluorophenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (13)

Yield, 90%; mp, 196 °C; IR (KBr), ν (cm⁻¹): 3576, 3260, 2931 (NH), 1531 (C=N), 1200 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 5.06 (s, 2H, H-9, CH₂O), 7.05 (t, 1H, H-6, J = 8.0 Hz, Ar-H), 7.09–7.13 (m, 1H, 5′, Ar-H), 7.22 (d, 1H, H-16, J = 8.0 Hz, Ar-H), 7.33 (ddd, 1H, H-6′, J = 1.0 Hz, 7.5 Hz, Ar-H), 7.41–7.52 (m, 4H, H-8, 14, 15, 3′ Ar-H), 7.65 (ddd, 1H, H-7, J = 1.5 Hz, 7.5 Hz, Ar-H), 7.83 (dd, 1H, H-5, J = 1.5 Hz, 7.5 Hz, Ar-H), 8.20 (s, 1H, H-17, CH=N), 8.29 (dd, 1H, H-13, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.67 (s, 1H, H-4, CH=C), 9.94 (s, 1H, H-21, NH–CS), 11.95 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 65.74, 104.43, 104.62, 104.83, 111.31, 111.34, 111.48, 113.60, 116.67, 119.25, 121.68, 122.87, 124.47, 125.26, 126.94, 129.07, 132.18, 132.41, 139.33, 140.32, 153.33, 157.20, 159.93, 177.94; HRMS calc. for C₂₄H₁₇F₂N₃O₃S 465.09588, found 465.09591. Anal. calcd for C₂₄H₁₇F₂N₃O₃S: C, 61.93; H, 3.68; N, 9.03. Found: C, 62.07; H, 3.70; N, 9.21.

4.14 N-(2-Methylphenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (14)

Yield, 87%; mp, 187 °C; IR (KBr), ν (cm⁻¹): 3575, 3261, 2930 (NH), 1537 (C=N), 1205 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 2.24 (s, 3H, CH₃), 5.05 (s, 2H, H-9, CH₂O), 7.05 (t, 1H, H-6, J = 8.0 Hz, Ar-H), 7.19–7.30 (m, 5H, H-8, 15, 3′, 4′, 5′, Ar-H), 7.40–7.44 (m, 2H, H-14, 6′, Ar-H), 7.47 (d, 1H, H-15, J = 8.5 Hz, Ar-H), 7.65 (ddd, 1H, H-7, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.82 (dd, 1H, H-5, J = 1.0 Hz, 7.0 Hz, Ar-H), 8.20 (s, 1H, H-17, CH=N), 8.31 (dd, 1H, H-13, J = 1.0 Hz, 7.5 Hz, Ar-H), 8.67 (s, 1H, H-4, CH=C), 9.97 (s, 1H, H-21, NH–CS), 11.76 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 17.20, 64.63, 112.42, 115.59, 118.18, 120.63, 122.01, 123.42, 124.17, 125.27, 125.92, 126.05, 127.98, 128.10, 129.42, 130.86, 131.30, 134.84, 137.48, 137.51, 139.14, 152.24, 156.01, 158.84, 176.05; HRMS calc. for C₂₅H₂₁N₃O₃S 443.1304, found 443.1306. Anal. calcd for C₂₅H₂₁N₃O₃S: C, 67.70; H, 4.77; N, 9.47. Found: C, 67.81; H, 4.95; N, 9.45.

4.15 N-(3-Methylphenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (15)²⁰

Yield, 90%; mp, 196 °C; IR (KBr), ν (cm⁻¹): 3576, 3264, 2933 (NH), 1530 (C=N), 1200 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 2.32 (s, 3H, CH₃), 5.05 (s, 2H, H-9, CH₂O), 7.01–7.06 (m, 2H, H-6, 5′, Ar-H), 7.21–7.26 (m, 2H, H-8, 2′, Ar-H), 7.38–7.44 (m, 4H, H-14, 15, 4′, 6′, Ar-H), 7.47 (d, 1H, H-15, J = 8.0 Hz, Ar-H), 7.65 (ddd, 1H, H-7, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.83 (dd, 1H, H-5, J = 1.0 Hz, 7.5 Hz, Ar-H), 8.21 (s, 1H, H-17, CH=N), 8.33 (dd, 1H, H-13, J = 1.5 Hz, 7.5 Hz, Ar-H), 8.67 (s, 1H, H-4, CH=C), 10.04 (s, 1H, H-21, NH–CS), 11.76 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 21.43, 65.72, 113.51, 116.67, 119.25, 121.69, 122.93, 123.36, 124.48, 125.25, 126.39, 126.68, 127.08, 128.31, 129.07, 132.08, 132.40, 137.75, 138.93, 139.42, 140.29, 153.33, 157.15 159.93, 176.15; HRMS calc. for C₂₅H₂₁N₃O₃S 443.1304, found 443.1307. Anal. calcd for C₂₅H₂₁N₃O₃S: C, 67.70; H, 4.77; N, 9.47. Found: C, 67.84; H, 4.81; N, 9.59.

4.16 N-(4-Methylphenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (16)

Yield, 91%; mp, 198 °C; IR (KBr), ν (cm⁻¹): 3572, 3264, 2931 (NH), 1531 (C=N), 1207 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 2.31 (s, 3H, CH₃), 5.04 (s, 2H, H-9, CH₂O), 7.06 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.16–7.17 (m, 2H, H-2′, 6′, Ar-H), 7.21 (d, 1H, H-16, J = 8.5 Hz, Ar-H), 7.41–7.44 (m, 4H, H-8, 14, 3′, 5′ Ar-H), 7.46 (d, 1H, H-15, J = 8.5 Hz, Ar-H), 7.66 (ddd, 1H, H-7, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.82 (dd, 1H, H-5, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.21 (s, 1H, H-17, CH=N), 8.33 (dd, 1H, H-13, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.67 (s, 1H, H-4, CH=C), 10.04 (s, 1H, H-21, NH–CS), 11.74 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 21.07, 65.71, 113.49, 116.67, 119.25, 121.68, 122.96, 124.48, 125.25, 126.25, 127.08, 128.97, 129.07, 132.04, 132.39, 134.90, 136.99, 138.86, 140.27, 153.32, 157.13, 159.92, 176.32; HRMS calc. for C₂₅H₂₁N₃O₃S 443.1304, found 443.1309. Anal. calcd for C₂₅H₂₁N₃O₃S: C, 67.70; H, 4.77; N, 9.47. Found: C, 67.71; H, 4.83; N, 9.49.

4.17 N-(4-Benzyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (17)

Yield, 90%; mp, 196–197 °C; IR (KBr), ν (cm⁻¹): 3576, 3263, 2933 (NH), 1531 (C=N), 1201 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 4.85 (d, 2H, H-22, CH₂NH), 5.03 (s, 2H, H-9, CH₂O), 7.03 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.19–7.25 (m, 2H, H-2′, 6′, Ar-H), 7.31–7.37 (m, 2H, H-16, 4′, Ar-H), 7.39–7.44 (m, 4H, H-8, 14, 3′, 5′ Ar-H), 7.47 (d, 1H, H-15, J = 8.5 Hz, Ar-H), 7.65 (ddd, 1H, H-7, J = 1.0 Hz, 8.5 Hz, Ar-H), 7.81 (dd, 1H, H-5, J = 1.0 Hz, 7.5 Hz, Ar-H), 8.18–8.19 (m, 2H, H-17, CH=N, H-13, Ar-H), 8.61 (s, 1H, H-4, CH=C), 9.09 (t, 1H, H-21, NH–CS, J = 6.5 Hz), 11.57 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 47.04, 65.67, 113.55, 116.66, 119.25, 121.65, 123.10, 124.49, 125.24, 126.63, 127.18, 127.70, 128.63, 129.06, 131.87, 132.38, 138.36, 139.97, 140.19, 153.31, 157.00, 159.91, 177.91; HRMS calc. for C₂₅H₂₁N₃O₃S 443.1304, found 443.1301. Anal. calcd for C₂₅H₂₁N₃O₃S: C, 67.70; H, 4.77; N, 9.47. Found: C, 67.91; H, 4.80; N, 9.50.

4.18 N-(4-Trifluoromethoxyphenyl)-2-({2-[(2-oxo-2H-1-benzopyran-3-yl)methoxy]phenyl}methylidene)hydrazine-1-carbothioamide (18)

Yield, 90%; mp, 152 °C; IR (KBr), ν (cm⁻¹): 3576, 3264, 2933 (NH), 1530 (C=N), 1202 (C=S). ¹H-NMR (DMSO-d⁶), δ (ppm): 5.05 (s, 2H, H-9, CH₂O), 7.06 (t, 1H, H-6, J = 7.5 Hz, Ar-H), 7.22 (d, 1H, H-8, J = 8.5 Hz, Ar-H), 7.37 (d, 2H, H-2′,6′, J = 8.5 Hz, Ar-H), 7.41–7.48 (m, 3H, H-13, 14, 15 Ar-H), 7.65 (ddd, 1H, H-7, J = 1.5 Hz, 8.5 Hz, Ar-H), 7.72 (d, 2H, H-3′, 5′, J = 8.5 Hz, Ar-H), 7.82 (dd, 1H, H-5, J = 1.0 Hz, 7.5 Hz, Ar-H), 8.21 (s, 1H, H-17, CH=N), 8.33 (dd, 1H, H-13, J = 1.5 Hz, 8.0 Hz, Ar-H), 8.69 (s, 1H, H-4, CH=C), 10.20 (s, 1H, H-21, NH–CS), 11.90 (s, 1H, H-19, NH–N); ¹³C NMR δ (ppm) 65.74, 113.53, 116.66, 119.24, 121.18, 121.67, 122.83, 124.43, 125.24, 127.08, 127.94, 129.06, 132.21, 132.39, 138.76, 139.43, 140.35, 145.78, 153.33, 157.22, 159.93, 176.34; HRMS calc. for C₂₅H₁₈F₃N₃O₄S 513.0970, found 513.0973. Anal. calcd for C₂₅H₁₈F₃N₃O₄S: C, 58.48; H, 3.53; N, 8.18. Found: C, 58.69; H, 3.56; N, 8.22.

Conflict of interest

The authors have declared no conflict of interest.

Acknowledgements

We are thankful to HEC (Higher Education Commission), Pakistan for financial support.

References

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Footnote

† Electronic supplementary information (ESI) available: The supplementary information includes copies of ¹H NMR and ¹³C NMR spectra of ligands, and spectral data for metal complexes. CCDC 1403640. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6ra12827k

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