Malaysian Journal of Analytical Sciences, Vol 27 No 2 (2023): 407 - 421

 

RECOVERED PALLADIUM COMPLEXES AS A POTENTIAL HOMOGENEOUS CATALYST FOR C-H FUNCTIONALIZATION AND ANTIBACTERIAL AGENT

 

(Kompleks Palladium Dipulihkan sebagai Pemangkin Homogen untuk Fungsi C-H dan Ejen Antibakteria)

 

Nur Anis Nabilah Mohd Fuzi1, Siti Khadijah Rahmat1, Muhammad Hazim Abdul Aziz1, Mohammad Noor Jalil1, Shamsul Bahrin Gulam Ali2*, and Khairil Anuar Jantan1*

 

1School of Chemistry and Environment,

Faculty of Applied Sciences

Universiti Teknologi MARA,

40450 Shah Alam, Selangor, Malaysia

2Faculty of Health Sciences, Bertam Campus

Universiti Teknologi MARA,

13200 Kepala Batas, Penang, Malaysia

 

*Corresponding author: sbahrin@uitm.edu.my & khairil0323@uitm.edu.my

 

 

Received: 24 August 2022; Accepted: 9 December 2022; Published:  19 April 2023

 

 

Abstract

The present study describes the utilization of simple and commercially available iodine and tetraphenylphosphonium salt as leaching agents to recover palladium (Pd) from waste. This study employed a model reaction assay that utilized Pd(0) metal powder to stimulate palladium leaching from spent automotive three-way catalyst (TWC). The palladium complexes, (Ph4P)2[Pd2I6], obtained were characterized with Fourier-transform infrared (FT-IR), ultraviolet-visible (UV-Vis) spectroscopy, nuclear magnetic resonances (NMR), thermogravimetric analysis (TGA), and elemental analysis. The recovered Pd complexes demonstrated excellent catalytic activity towards the methoxylation of benzo[h]quinoline. Furthermore, a lower to moderate product yield was recorded for the ethoxy- and isopropoxylation of benzo[h]quinoline. The C-H functionalization of 8-methylquinoline catalyzed by the obtained palladium complexes also documented a moderate product yield (< 65%) after 6 hours of reaction. The antibacterial activities of the (Ph4P)2[Pd2I6] were evaluated through a disk diffusion test, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) assays. Among the gram-positive and -negative bacteria evaluated, Klebsiella pneumoniae exhibited the highest sensitivity to the synthesized (Ph4P)2[Pd2I6] at all concentrations. The MIC concentrations for all assessed bacteria ranged from 0.156 to 1.25 mg/mL. Moreover, bacterial growth was detected in all MBC plates, thus indicating that the (Ph4P)2[Pd2I6] possessed a bacteriostatic effect and not a killing attribute.

 

Keywords: recovered palladium, palladium catalyst, antibacterial activity

 

Abstrak

Kajian ini menghuraikan mengenai penggunaan iodin dan garam tetrafenilphosphonium yang mudah dan boleh didapati secara komersial sebagai agen larut lesap dalam proses pemulihan paladium (Pd) daripada sisa terbuang. Kajian ini melaksanakan ujian berdasarkan model tindak balas yang menggunakan serbuk logam Pd(0) untuk merangsang proses larut lesap Pd dari pemangkin tiga hala automotif (TWC) terpakai. Spesies molekul kompleks Pd dipulihkan, (Ph4P)2[Pd2I6], yang diperoleh dicirikan melalui Fourier-transform inframerah (FT-IR), spektroskopi ultra ungu-nampak (UV-Vis), resonans magnet nuklear (NMR), analisis termogravimetrik (TGA) dan analisis unsur. Kompleks Pd dipulihkan yang diperoleh tersebut menunjukkan aktiviti pemangkin yang sangat baik bagi ke arah metoksilasi benzo[h]kuinolin. Selain itu, hasil produk yang sederhana telah direkodkan bagi etoksi dan isopropoksilasi benzo[h]kuinolin. Kefungsian C-H sebagai pemangkinan 8-metilquinolin oleh kompleks Pd dipulihkan juga merekodkan hasil produk yang sederhana (< 65%) selepas tindak balas selama 6 jam. Aktiviti antibakteria (Ph4P)2[Pd2I6] tersebut dinilai melalui ujian resapan cakera, kepekatan perencatan minimum (MIC), dan ujian kepekatan bakteria minimum (MBC). Antara kesemua bakteria gram-positif dan -negatif yang diuji, Klebsiella pneumoniae menunjukkan sensitiviti tertinggi kepada (Ph4P)2[Pd2I6] pada semua kepekatan. Kepekatan MIC untuk semua bakteria yang diuji direkod dalam julat 0.156 hingga 1.25 mg/ml. Tambahan pula, pertumbuhan bakteria yang dikesan dalam semua plat MBC menunjukkan bahawa (Ph4P)2[Pd2I6] mempunyai kesan bakteriostatik dan tidak membunuh.

 

Kata kunci: paladium dipulihkan, mangkin paladium, aktiviti antibakteria

 

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