Nanoscale chirality generated in zinc(II) orthophosphate clusters: evidence by vibrational circular dichroism

• Published in: Nanoscale 2024-11, Vol.16 (44), p.20589-20595
• Main Authors: Aisawa, Sumio, Horiguchi, Nami, Chida, Chika, Sang, Jing, Hirahara, Hidetoshi, Yamagishi, Akihiko, Sato, Hisako
• Format: Article
• Language: English
• Subjects: Chirality; Dehydration; Dichroism; Differential thermal analysis; Diffraction patterns; Hydroxides; Hydroxyl groups; Roasting; Room temperature; Zinc oxide; Zinc phosphate
• ISSN: 2040-3364; 2040-3372; 2040-3372
• DOI: 10.1039/d4nr03809f

Layered zinc(II) hydroxides (LZH) intercalating the deprotonated forms of -(-) or -(+)-1,1'-binaphthyl-2,2'-diyl hydrogenphosphate (denoted as - or -BNDHPH, respectively) were prepared from Zn(NO ) at pH 5 and 60 °C by the mixing method. The obtained hybrid compounds (denoted as - or -BNDHP /LZH, respectively) were heated from room temperature up to 800 °C under nitrogen atmosphere. According to the thermal gravimetric/differential thermal analysis measurements, hydroxyl groups were dehydrated at 270-400 °C, followed by the decomposition of organic components at 420-600 °C. X-ray diffraction patterns and scanning electron microscopy images indicated that the final products were a mixture of α-Zn (PO ) , ZnO crystals and non-crystalline zinc(II) orthophosphates. Vibrational circular dichroism (VCD) spectra were recorded before and after calcination. Before calcination, - or -BNDHP /LZH exhibited VCD peaks assigned to intercalated - or -BNDHP . The calcined products exhibited several VCD peaks in the range of 900-1200 cm , maintaining the mirror-image relationship between -BNDHP /LZH and -BNDHP /LZH used as starting materials. The observed peaks were assigned to the PO (symmetric), -POO , and PO (asymmetric) stretching vibrations of the PO groups. According to theoretical simulations, the observed VCD activity can be rationalised in terms of vibrational coupling between two PO groups in a generated chiral zinc(II) orthophosphate cluster.