Synthesis and antiviral activities of novel penta-1,4-diene-3-one oxime derivatives bearing a pyridine moiety

A series of novel penta-1,4-diene-3-one oxime ether derivatives bearing a pyridine moiety were designed and synthesized, and their antiviral activities against tobacco mosaic virus (TMV) were evaluated. The results of the biological assay indicated that most of the title compounds exhibit good antiviral activities against TMV at 500 μg/mL. In particular, the title compounds 5c, 5j, 5o and 5p showed remarkable curative activities against TMV, with EC₅₀ values of 274.8, 299.2, 251.8 and 287.7 μg/mL, respectively, which were superior to that of ribavirin (379.8 μg/mL). This study indicates that penta-1,4-diene-3-one oxime ether derivatives bearing a pyridine moiety can serve as potential alternative templates in the search for novel, highly efficient, anti-plant viral agents.     

Synthesis and structure elucidation of some new azo dye from hydroxyquinolin-2(<Emphasis Type="Italic">1H</Emphasis>)-one derivatives and their antimicrobial evaluation

The aim of the work is synthesis of some novel azo dye from 1,2-dihydro-4-hydroxy-2-oxoquinoline-6-sulfonic acid (3), 4-hydroxy-6-methoxyquinolin-2(1H)-one (4), and 4-hydroxy-6-nitroquinolin-2(1H)-one (5). The prepared compounds were screened for antibacterial against Staphylococcus aureus, Escherichia coli, and antifungal activity against Candida sp., Aspergillus multi and Aspergillus niger. The structure of newly compounds was characterized by ¹H-NMR, IR and elemental analysis.     

Synthesis of novel 1,3,4-oxadiazole derivatives containing diamides as promising antibacterial and antiviral agents

In this paper, a variety of novel 1,3,4-oxadiazole derivatives possessing diamides were synthesized and tested for their antibacterial and antiviral activity. Preliminary antibacterial assays indicated that some intermediates and title compounds displayed excellent inhibition effects against plant pathogens Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac). Further studies revealed that compound H15 exhibited the strongest activities against Xoo and Xac with minimal EC₅₀ values of 0.7 and 5.9 μg/mL, respectively. Antiviral bioassays suggested that some of these structures displayed appreciable curative activities and moderate protective effects against tobacco mosaic virus (TMV) in vivo. Among them, compound H8 exerted the best chemotherapeutic effect against TMV with the curative rate of 60.0% at 500 µg/mL, which was comparable with those of commercial agricultural antiviral agent ningnanmycin (54.2%). Given their significant biological activities, this kind of compound could serve as new leading compounds in the study of antibacterial and antiviral chemotherapy.     

Synthesis,SAR and in vitro therapeutic potentials of thiazolidine-2,4-diones

Background

Thiazolidinedione is a pentacyclic moiety having five membered unsaturated ring system composed with carbon, oxygen, nitrogen and sulfur molecules at 1 and 3 position of the thiazole ring and widely found throughout nature in various form. They favourably alter concentration of the hormones secreted by adipocytes, particularly adiponectin. They also increase total body fat and have mixed effects on circulating lipids. Thiazolidinedione nucleus is present in numerous biological moieties and has different pharmacological activities likes, e.g. antimalarial, antimicrobial, antimycobacterial, anticonvulsant, antiviral, anticancer, anti-inflammatory, antioxidant, anti-HIV (human immunodeficiency virus) and antituberculosis.

Results and discussion

The synthesized compounds were screened for their in vitro antimicrobial potential against Gram (positive and negative) bacterial and fungal strains by tube dilution technique. In this series, compound 10 exhibited significant antimicrobial activity against B. subtilis and S. aureus with MIC?=?4.2?×?10^?2 µM/ml, compound 15 showed significant activity against K. pneumonia with MIC?=?2.60?×?10^?2 µM/ml and compound 4 displayed potent antibacterial activity against E. coli with MIC?=?4.5?×?10^?2 µM/ml. Compound 10 had most potent antifungal activity against C. albicans and A. niger with MIC?=?4.2?×?10^?2 µM/ml. Compounds 12 and 15 were found as most active antidiabetic agents having IC₅₀?=?27.63 μg/ml and 22.35 μg/ml, respectively, using DPPH assay. Antioxidant activity results indicated that compounds 3 and 9 displayed good antioxidant agent with IC₅₀?=?29.04 μg/ml and 27.66 μg/ml respectively, using α amylase assay.

Conclusion

All the synthesized derivatives exhibited good antimicrobial, antidiabetic and antioxidant activities using specific methods then compared with mentioned standard drugs. Especially, compounds 3, 4, 9, 10, 12 and 15 displayed highest activity. Structure activity relationship demonstrated that presence of electron withdrawing group (o-NO₂, p-Cl, p-Br) enhanced the antibacterial activity against E. coli as well as increased the antioxidant activity while the presence of electron releasing group (o/p-OCH₃, 3,4,5-trimethoxy) enhanced the antibacterial activity against S. aureus, B. subtilis, S. typhi, K. pneumonia, C. albicans and A. niger as well as the antidiabetic activity.

     

Synthesis of novel coumarin substituted amide derivatives and their antibacterial activities

A series of novel coumarin substituted amide derivatives were synthesized and evaluated for their antibacterial activities. Result indicated that compounds 3f, 3g, 3h, 3i, 3j, 3k, 3l, 3m, 3n, 3o and 3q exhibited excellent antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas citri subsp. Citri (Xcc) in vitro, which were better than those of commercial agricultural antibacterial thiodiazole-copper. The title compounds with electron-withdrawing group showed better antibacterial activities than those of compounds with electron-donating group, and the title compounds bearing the same substituent group exhibited better antibacterial activities against Xcc than antibacterial activities against Xoo.     

Synthesis and anticancer activities of 1,4-phenylene-bis-<Emphasis Type="Italic">N</Emphasis>-acetyl- and <Emphasis Type="Italic">N</Emphasis>-phenylpyrazoline derivatives

Novel 1,4-phenylene-bis-N-acetyl- (3a–h) and bis-N-phenylpyrazoline derivatives (4a–h) were obtained by addition of hydrazine hydrate and phenylhydrazine to bis-chalcone derivatives (1a–h) in acetic acid and acetic acid/ethanol for 4 and 8 h in reflux conditions, respectively. The structures of the obtained bis-N-acetylpyrazoline and bis-N-phenylpyrazoline derivatives were characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic methods and elemental analysis. Compounds 3a–h and 4a–h were investigated to evaluate their anticancer activities against C6 (rat brain tumor cells) and HeLa (human uterus carcinoma) in vitro using a dose-dependent assay from 5 to 100 μM with 5-fluorouracil (5-FU) as standard anticancer drug. Compound 3a showed higher cell-selective activity compared with 5-FU against HeLa cells. Compounds 3a–h (except 3d) were shown to have better activities than 5-FU against both cells, particularly at high concentration. Compound 4c showed higher cell-selective activity compared with 5-FU against C6 cells. Compound 3a may be particularly promising as an anticancer drug against HeLa cells.     

Synthesis and antibacterial and antifungal activities of <Emphasis Type="Italic">N</Emphasis>-(tetra-<Emphasis Type="Italic">O</Emphasis>-acetyl-β-<Emphasis Type="SmallCaps">d</Emphasis>-glucopyranosyl)thiosemicarbazones of substituted 4-formylsydnones

Background

Sydnone is a heterocycle that exhibits remarkable pharmacological activities, including antimicrobial, anti-inflammatory, analgesic, antipyretic and antioxidant activities. Thiosemicarbazones are of compounds that contain the –NHCSNHN=C< linkage group and are considerable interest because they exhibit important chemical properties and potentially beneficial biological activities. Similarly, thiosemicarbazones having carbohydrate moieties also exhibit various significant biological activities.

Results

The compounds of 3-formyl-4-phenylsydnones were obtained by Vilsmeyer-Haack’s formylation reaction and were transformed into thiosemicarbazones by condensation reaction with N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazide. Reaction were performed in the presence glacial acetic acid as catalyst using microwave-assisted heating method. Reaction yields were 43?85 %. The antimicrobial activities of these thiosemicarbazones were screened in vitro by using agar well diffusion and MIC methods. Among these thiosemicarbazones, compounds 4k, 4l, 4m and 4n were more active against all tested bacterial strains, especially against S. epidermidis, B. subtilis and E. coli. The MIC values in these cases are 0.156, 0.156 and 0.313 μg/mL, respectively. All compounds showed weak to moderate antifungal activity against C. albicans and A. niger than nystatin (MIC = 0.156?0.625 μg/mL vs. MIC = 0.078 μg/mL of nystatin), and thiosemicarbazones 4l, 4m and 4n exhibited significant activity with MIC = 0.156 μg/mL. These compounds also had good antifungal activity against F. oxysporum similarly to nystatin (MIC = 0.156 μg/mL). Among the tested compounds having halogen group 4k, 4l, 4m and 4n showed highest activity against three strains of fungal organisms.

Conclusions

In summary, we have developed a clean and efficient methodology for the synthesis of novel thiosemicarbazone derivatives bearing sydnone ring and d-glucose moiety; the heterocyclic and monosaccharide system being connected via ?NH?C(=S)NH?N=C< linker using molecular modification approach. The methodology could be further extended and used for the synthesis of other thiosemicarbazones of biological importance. 4-Formyl-3-arylsydnone N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazones have been synthesized under microwave-assisted heating conditions. Almost all obtained compounds showed remarkable activities against the tested microorganisms. Among the tested compounds having halogen group 4k, 4l, 4m and 4n showed highest activity against all tested strains of bacterial and fungal organisms.

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Graphical abstract:Synthesis and antibacterial and antifungal activities of N-(tetra-O-acetyl-β-D-glucopyranosyl)thiosemicarbazones of substituted 4-formylsydnones

     

1-Aryl-3-(1<Emphasis Type="Italic">H</Emphasis>-imidazol-1-yl)propan-1-ol esters: synthesis,anti-<Emphasis Type="Italic">Candida</Emphasis>potential and molecular modeling studies

Background

An increased incidence of fungal infections, both invasive and superficial, has been witnessed over the last two decades. Candida species seem to be the main etiology of nosocomial fungal infections worldwide with Candida albicans, which is commensal in healthy individuals, accounting for the majority of invasive Candida infections with about 30-40% of mortality.

Results

New aromatic and heterocyclic esters 5a-k of 1-aryl-3-(1H-imidazol-1-yl)propan-1-ols 4a-d were successfully synthesized and evaluated for their anti-Candida potential. Compound 5a emerged as the most active congener among the newly synthesized compounds 5a-k with MIC value of 0.0833 μmol/mL as compared with fluconazole (MIC value >1.6325 μmol/mL). Additionally, molecular modeling studies were conducted on a set of anti-Candida albicans compounds.

Conclusion

The newly synthesized esters 5a-k showed more potent anti-Candida activities than fluconazole. Compounds 7 and 8 revealed significant anti-Candida albicans activity and were able to effectively satisfy the proposed pharmacophore geometry, using the energy accessible conformers (E_conf?<?20 kcal/mol).

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Synthesis and antibacterial evaluation of novel Schiff base derivatives containing 4(3<Emphasis Type="Italic">H</Emphasis>)-quinazolinone moiety

A series of novel Schiff base derivatives containing 4(3H)-quinazolinone moiety were synthesised and their antibacterial activities against tobacco and tomato bacterial wilts evaluated in vitro. Out of the synthesised compounds, 5g, 5j, 5n, 5m and 5p exhibited excellent antibacterial activities against tobacco bacterial wilt, with half maximal effective concentrations (EC50): 160.34, 158.03, 125.94, 148.09 and 133.67 (all in εg mL^?1), respectively, which were better than the EC50 of thiodiazole–copper (216.70 εg mL^?1). Compounds 5j, 5n and 5o also showed good antibacterial activities against tomato bacterial wilt, with EC50 of 95.20, 90.03 and 83.21 (all in εg mL^?1) respectively, which were better than the EC50of thiodiazole–copper (99.80 εg mL^?1). These compounds may prove to be useful as potential antibacterial agents.     

Kumada cross coupling reaction based synthesis,antimicrobial and computational studies of 6-aryl-2-phenyl-3-methylquinazolin-4(3<Emphasis Type="Italic">H</Emphasis>)-ones

Nickel catalyzed Kumada cross coupling reaction, a novel synthetic method for the synthesis of 6-aryl-2-phenyl-3-methylquinazolin-4(3H)-ones (6a–6i), was carried out by condensing 6-iodo-2-phenyl-3-methyl-quinazolin-4(3H)-one (4) with various 6-aryl/heteroaryl Grignard reagents. Molecular properties of compounds 4 and 6a–6i were studied using semiempirical PM3 computational method. The optimized geometry of the product 6 indicated that the aryl group at the position 6 was not coplanar with respect to either quinazolinone ring or phenyl group at 2 position. Compounds 6a–6i were screened for their activity against bacteria and fungi.     

Synthesis,characterization, crystal structures,and antibacterial activity of oxidovanadium(V) complexes with mixed ligands

Two new oxidovanadium(V) complexes, [VO(L)(Ehp)] (I) and [VO(L)(Aha)] (II), where L is the dianionic form of 4-bromo-N'-(4-oxopentan-2-ylidene)benzohydrazide (H₂L), Ehp is the monoanionic form of 2-ethyl-3-hydroxy-4H-pyran-4-one (HEhp), and Aha is the monoanionic form of acetohydroxamic acid (HAha), were prepared and characterized by elemental analysis, infrared and electronic spectra, and ¹H NMR spectra. Structures of the complexes were further confirmed by single crystal X-ray diffraction (CIF files CCDC nos. 1477847 (I), 1477850 (II)). H2L coordinates to the V atom through the two enolic O atoms and the imino N atom. The ligands Ehp and Aha coordinate to the V atoms through bidentate OO donor set. The V atoms of the complexes are in octahedral coordination, with the oxo group furnished the octahedral geometry. The complexes show effective antibacterial activity against Bacillus subtilis.     

Synthesis,antifungal and insecticidal activity of novel [1,2,4]triazolo[4,3-<Emphasis Type="Italic">a</Emphasis>]pyridine derivatives containing a sulfide substructure

A series of [1,2,4]triazolo[4,3-a]pyridine derivatives bearing a sulfide substructure was designed, synthesized and characterized via ¹H·NMR, ¹³C·NMR, IR and elemental analyses. Bioassay Results indicated some of the derivatives displayed good fungicidal activity on Rhizoctonia cerealis, moderated insecticidal activity against Plutella xylostella and good insecticidal activity on Helicoverpa armigera. The inhibitory effects of compounds 4g and 4u against Rhizotonia cerealis were 70.9% at 50 μg mL^?1; the IC₅₀ values of compounds 4d and 4s against Plutella xylostella were 43.87 and 50.75 μg mL^?1, respectively. And the IC₅₀ values of compounds 4d, 4q, and 4s on Helicoverpa armigera were 58.3, 77.14 and 65.31 μg mL^?1, respectively, which were better than that of commercial chlorpyrifos (103.77 μg mL^?1).     

Synthesis,antimicrobial evaluation,and docking studies of some novel benzofuran based analogues of chalcone and 1,4-benzodiazepine

A series of novel {5-[4-hydroxy-3-(4-phenyl-2,3-dihydro-1H-benzo[b][1,4]diazepin-2-yl)benzyl]- benzofuran-2-yl}(phenyl)methanones (5a–5g) were prepared by the condensation of (E)-3-{5-[(2- benzoylbenzofuran-5-yl)methyl]-2-hydroxyphenyl}-1-phenylprop-2-en-1-one (chalcone) (4a) with various substituted o-phenylene diamines in the presence of oxalic acid as catalyst. The structures of all compounds were characterized by FTIR, ¹H NMR, ¹³C NMR, and MS. The representative examples were screened in vitro for antimicrobial activity. Among all compounds 4g and 5g showed potent antibacterial activity, 4b and 5g showed good antifungal activity. The data was further compared with structure based investigations using docking studies with the crystal structure of adenosine-5'-(β,γ-imido)triphosphate (2ONJ) from Staphylococcus aureus for antibacterial activity and trypsin (1FY5) protein from Fusarium oxysporum for the antifungal activity. The score values estimated by genetic algorithm were found to have a good correlation with the experimental inhibitory potencies.     

Discovery of natural berberine-derived nitroimidazoles as potentially multi-targeting agents against drug-resistant <Emphasis Type="Italic">Escherichia coli</Emphasis>

A series of natural berberine-derived nitroimidazoles as novel antibacterial agents were designed, synthesized and characterized by nuclear magnetic resonance (NMR), infrared spectra (IR), and high resolution mass spectra (HRMS) spectra. The antimicrobial evaluation showed that some target molecules exhibited moderate to good inhibitory activities against the tested bacteria and fungi including clinical drug-resistant strains isolated from infected patients. Especially, 2-fluorobenzyl derivative 8f not only gave strong activity against drug-resistant E. coli with the minimal inhibitory concentration (MIC) value of 0.003 mM, 33-fold more active than norfloxacin, but also exhibited low toxicity toward RAW 264.7 cells and less propensity to trigger resistance. The aqueous solubility and ClogP values of target compounds were investigated to elucidate the structureactivity relationships. Molecular docking and quantum chemical studies for compound 8f rationally explained its antibacterial effect. The further exploration of antibacterial mechanism revealed that the highly active compound 8f could effectively permeabilize E. coli cell membrane and intercalate into DNA isolated from resistant E. coli to form 8f-DNA complex that might block DNA replication to exert the powerful bioactivities. Compound 8f could also selectively address resistant E. coli from a mixture of various strains.     

Molecular and crystal structures of adducts (Cp<Subscript>2</Subscript>YCl)<Subscript>2</Subscript>L (L = 2THF,DME, 1,4-dioxane)

The adducts [Cp₂Y(μ-Cl)]₂ · 2THF (5), {[Cp₂Y(μ-Cl)]₂ · 1,4-dioxane}_n (6), and Cp₂Y(DME)(μ-Cl)(Cl)YCp₂ (7) have been synthesized and studied by X-ray crystallography. In 5, the (Cp₂YCl)₂ moiety is coordinated to two THF molecules (d _(Y-O) = 2.478 Å); in 6 the (Cp₂YCl)₂ dimers are linked by 1,4-dioxane to form a polymer chain (d _(Y-O) = 2.601 Å). In asymmetric adduct 7, the DME molecule is bound through both O atoms to the same Y atom (d _(Y-O) = 2.382 and 2.448 Å), and one of the chlorine atoms is bridging and the other chlorine atom is terminal.     

Synthesis and crystal structures of tetraacetylethylenediamine and <Emphasis Type="Italic">N</Emphasis>-(2-ammoniumethyl)carbamate

Two ethylenediamine derivatives—N-(2-ammoniumethyl)carbamate HN(COO^?)CH₂CH₂N⁺H₃ (I) and tetraacetylethylenediamine (H₃CC(O))₂NCH₂CH₂N(C(O)CH₃)₂ (II) (synthesized for the first time)—have been synthesized and characterized by X-ray crystallography. Compounds I and II are isolated as minor admixtures upon an attempt to synthesize ethylenediamine complexes of lanthanum and neodymium nitrates, respectively. The crystals of I and II are monoclinic: a = 7.778 Å, b = 8.060 Å, c = 7.568 Å, β = 95.73°, Z = 4, space group P2₁/c (I); a = 5.946, b = 10.255, c = 9.343 Å, β = 95.72°, Z = 2, space group P2₁/c (II). The bond lengths and bond angles lie within the corresponding standard values. Compounds I and II have different conformations of the N-C-C-N ethylenediamine moiety: gauche in I and trans in II, and the corresponding torsion angles are equal to 66.6° and 180°, respectively.     

Potent antibacterial agents: pyridinium-functionalized amphiphiles bearing 1,3,4-oxadiazole scaffolds

Through tuning and optimizing the phenyl substituents and alkyl length, a series of pyridinium-functionalized amphiphiles possessing potent antibacterial activity toward three types of plant pathogenic bacteria were obtained. Investigations on the inhibition effect of substituents on the phenyl ring towards the bioactivity suggested that the substitutional group was not the crucial factor for the bioactivity. In comparison, the antibacterial effects could be significantly enhanced with increasing the length of alkyl chains. Among these amphiphiles, 6c, 6f, 6h, 6i, 6k, 6l, 6n, and 6q exhibited remarkable inhibition activities against the three pathogenic bacteria with the half-maximal effective concentration (EC₅₀) values within 0.128–1.98 µg/mL. Furthermore, the minimum EC₅₀ values against the pathogens Xanthomonas oryzae pv. oryzae and Xanthomonas axonopodis pv. citri could reach to 0.128 and 0.403 µg/mL, respectively, which were decreased about four times than those of our previous results. Given their simple synthesis and biocidal antibacterial activity, this kind of amphiphiles could be developed as promising bactericides against plant bacterial diseases.     

Lanthanide contraction effect on the crystal structures of 2D lanthanide coordination polymers based on 2-(trifluoromethyl)-1<Emphasis Type="Italic">H</Emphasis>-imidazole-4,5-dicarboxylic acid

A series of new two-dimensional (2D) lanthanide(III) coordination polymers, namely {[Ln₂(μ ₂-HTFMIDC)₃(DMA)₄] · 2H₂O} _n [Ln = Pr (1); Nd (2); Sm (3); Eu (4); H₃TFMIDC = 2-(trifluoromethyl)-1H-imidazole-4,5-dicarboxylic acid, DMA = N,N′-dimethylacetamide] for type I and {[Ln₂(μ ₂-HTFMIDC)₃(DMA)₂(H₂O)₂] · DMA} _n [Ln = Eu (5); Gd (6)] for type II, have been successfully prepared under solvothermal conditions and structurally characterized for the first time. Both two types of structures exhibit similar 2D honeycomb-like networks, which are constructed by the linkages of μ ₂-HTFMIDC^2? bis-(bidentate) bridging ligands and Ln(III) metal centers. However, slightly different ABAB stacking fashions of the 2D layers and distinctly different hydrogen bonding interactions between the neighboring 2D layers are observed in crystal structures of type I and type II, which may be attributed to the lanthanide contraction effect. Meanwhile, the solid-state luminescent properties of 4 and 5 have been also investigated.     

Synthesis and antimicrobial activity of novel fused [1,2,4]triazino[5,6-<Emphasis Type="Italic">b</Emphasis>]indole derivatives

Synthesis of new fused systems of triazino[5,6-b]indole starting with preparation of 3-amino[1,2,4]-triazino[5,6-b]indole 1 by reaction of isatin with 2-aminoguanidinium carbonate in boiling acetic acid is presented [1]. Intermediate compound 1 reacted with aldehyde, ethyl chloroformate, triethyl orthoformate, and ninhydrine and gave new heterotetracyclic nitrogen systems, such as 3-(N ²-guanidinylimino)indole-2(1H)-one 2, 3-(N-ethoxycarbonylamino)-4H-[1,2,4]triazino[5,6-b]indole 3, 3-(N-ethoxymethyleneamino)-4H-[1,2,4]-triazino[5,6-b]indole 4, 3-(hydrazinothiocarbonylamino)-4H-[1,2,4]triazino[5,6-b]indole 5, respectively. N-(1,3-dioxoindene-2-ylidene)-4H-[1,2,4]triazino[5,6-b]indol-3-amine 6 was synthesized by reaction of compound 1 with aldehyde, ethyl chloroformate, triethyl orthoformate, and ninhydrine. New fused indole systems, pyrimido[2′,1′:3,4][1,2,4]triazino[5,6-b]indol-3(4H)-one 8, 9, 11, 12 and 1H-imidazo[2′,1′:3,4][1,2,4]triazino-[5,6-b]indol-2(3H)-one 10, were synthesized in the reaction of the intermediate 1 with bifunctional compounds. Structures of the products were elucidated from their elemental analysis and spectral data (IR, ¹H and ¹³C NMR and mass spectra). Antimicrobial activity of some synthesized compounds was tested.     

Directed assembly of cobalt(II) 1-H-indazole-3-carboxylic acid coordination networks by bipyridine and its derivatives: structural versatility,electrochemical properties,and antifungal activity

This paper describes the hydrothermal synthesis, full characterization, and architectural diversity of three intriguingly bioactive cobalt–organic frameworks, namely, 3D [Co(HL ^? )₂(BPY)] _n ·4nH₂O (1), 2D [Co(HL ^? )₂(BPE)] _n (2), and 2D [Co(HL ^? )₂(DPP)] _n (3) coordination polymers, synthesized through a mixed ligand strategy using H ₂ L (1-H-indazole-3-carboxylic acid) as a main structural block and the flexible bipyridine and its derivatives (BPY = 4,4′-bipydine, BPE = 1,2-bis(4-pyridyl)ethane, DPP = 1,3-bis(4-pyridyl)propane) as auxiliary ligand sources. Complexes 1–3 were isolated as air stable and slightly soluble crystalline solids and characterized using elemental analysis, FT-IR, electrochemical technique, thermogravimetric analysis, powder X-ray diffractometer, and single-crystal X-ray crystallography. The bipyridine derivatives played key roles in defining the structural space group and dimensionality feature of the obtained networks. The abundant H-bonding and π–π stacking interactions in complexes 1–3 gave rise to their intricate metal–organic structures of 3D (1), 2D (2), and 2D (3). In addition, the solutions of complexes 1–3 showed profound antifungal activities against the selected strain of Colletotrichum musae compared with the controlled group using benomyl as a traditional agrochemical fungicide.