Volume 278, May 2026, 113244Author links open overlay panel, , , , , , , , , Highlights•

Preparation of the complexes [Mo(η3-C3H5)X(CO)2(3-(2-pyridyl)pyrazole)] (X = Cl, Br).

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Myoglobin assay reveals a steady release of CO from the complexes in aqueous media.

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The Cl complex (1) shows bactericidal activity against E. coli and S. aureus strains.

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Cytotoxicity assays with melanoma (A375) and normal (HaCat keratinocytes) cell lines.

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Complex 1 shows selective cytotoxicity and thus antitumor potential against melanoma.

Abstract

Molybdenum-based CO-releasing molecules (CORMs) are attracting interest for biological and therapeutic applications. In this work two new complexes, [Mo(η3-C3H5)X(CO)2(Hpypz)] [X = Cl (1), Br (2); Hpypz = 3-(2-pyridyl)pyrazole] have been synthesized, characterized, and evaluated for their CO-release capacity, as well as antimicrobial and anticancer potential. The evaluation of the CO-release properties by the deoxymyoglobin‑carbonmonoxymyoglobin assay showed that the two complexes are comparably slow CO releasers in aqueous systems, showing a half-life of several hours, and sustained CO release over the course of the assay (6 h). Studies of biological activity were performed with complex 1 due to its better aqueous solubility. The antibacterial activity was investigated by determination of the minimum inhibitory and minimum bactericidal concentrations with the microdilution assay for gram-positive methicillin-resistant Staphylococcus aureus (MRSA) and gram-negative Escherichia coli strains. Complex 1 displayed appreciable concentration-dependent bactericidal activity against both strains. The cytotoxicity of complex 1 was evaluated on human melanoma cells (A375) and immortalized nontumorigenic keratinocytes (HaCaT). Complex 1 exhibited selective cytotoxicity, significantly reducing the cell viability of A375 cells in a dose-dependent manner while having a lower effect on HaCaT cells, suggesting its antitumor potential against melanoma. In contrast, the precursor complex [Mo(η3-C3H5)Cl(CO)2(CH3CN)2] showed reduced activity against A375 cells and higher toxicity toward HaCaT cells, highlighting the beneficial impact of the bidentate 3-(2-pyridyl)pyrazole ligand.

Graphical abstractDownload: Download high-res image (223KB)Download: Download full-size imageKeywords

CO-releasing molecules

Molybdenum carbonyl complexes

Myoglobin assay

Antibacterial activity

Antitumoral activity

Melanoma

AbbreviationsA375

amelanotic skin melanoma cell line

ANOVA

analysis of variance

Ar-BIAN

bis(aryl)acenaphthenequinonediimine

ATR

attenuated total reflectance

BC

bacterial growth control

Cp

cyclopentadienyl, η5-C5H5

CORMs

CO-releasing molecules

DMEM

Dulbecco's Modified Eagle's Medium

dppz

dipyrido[3,2-a:2′,3′-c]phenazine

HaCaT cells

immortalized human epidermal keratinocytes cell line

Hpypz

3-(2-pyridyl)pyrazole

IC50

50% inhibition concentration

FT-IR

Fourier transform infrared

MbCO

carbonmonoxy-myoglobin

MBC

minimum bactericidal concentration

MIC

minimum inhibitory concentration

MH

Mueller-Hinton II Broth

MLCT

metal-to-ligand charge transfer

MRSA

methicillin-resistant Staphylococcus aureus

MTT

3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide

NMR

nuclear magnetic resonance

PBS

phosphate buffered saline

UV-Vis

ultraviolet-visible.

© 2026 The Authors. Published by Elsevier Inc.