Versatile photocatalytic activities of indenoquinoxalines for dye reduction, single-crystal nucleation, and MNP formation with iron scrap under sunlight

Abstract

In this work, 11H-indeno[1,2-b]quinoxalin-11-one (IQ), 7-nitro-11H-indeno[1,2-b]quinoxalin-11-one (NIQ), and 7-chloro-11H-indeno[1,2-b]quinoxalin-11-one (CIQ) as indenoquinoxalines (IQPs) and 7-nitro-2′-(4-nitrophenyl)-5′,6′,7′,7a′-tetrahydrospiro[indeno[1,2-b]quinoxaline-11,3′-pyrrolizine]-1′,1′(2′H)-dicarbonitrile (SIQPNO₂) spiroheterocyclics were synthesized. These molecules photocatalytically reduced methylene blue (MB), methyl orange (MO), brilliant blue R (BBR), and Rhodamine B (RhB) in aqueous acetonitrile (aq-ACN) under sunlight (SL) for the first time. The IQPs and SIQPNO₂ with a lanthanide graphene oxide template (LGT) of lanthanide sulfide nanorods (Ln₂S₃, Ce₂S₃, Tb₂S₃, and Ho₂S₃) photocatalytically reduced the dyes. IQ alone reduced MB in ∼2 min, while with LaGT, CeGT, TbGT, and HoGT in 7, 10, 11, and 13 min, respectively. NIQ and CIQ alone photocatalytically reduced MB in 18 and 32 min, while with LaGT, CeGT, TbGT, and HoGT in 18, 31, 23, and 28 min and 33, 55, 45, and 51 min, respectively. IQ with CO₂ photocatalytically reduced MB and QHIn in 90 s and 17 min unlike 2 and 24 min without CO₂, respectively. SIQPNO₂ alone reduced MB in 190 min, while with CeGT, TbGT, HoGT, and LaGT in 242, 225, 197, and 88 min, respectively. IQ with LaGT photocatalytically reduced MB in 7 min, while SIQPNO₂ with LaGT in 88 min. IQ received maximum photon (hv) producing robust redox cycles (ROCs) compared to SIQPNO₂. SIQPI, SIQPII, SIQPIII, and SIQPNO₂ (SIQPs) individually reduced MB in 95, 43, 54, and 190 min, while SIQPs with NIQ in 63, 35, 47, and 64 min, respectively. IQ with Fe scrap in ACN developed a single crystal in 2 weeks, while in 2 : 8, 3 : 7, 5 : 5, 7 : 3, and 8 : 2 aq-ACN media, the magnetic nanoparticles (MNPs) developed at normal temperature and pressure (NTP).