Huang-Ling Lin, Meng-Zhen Xu, Tian-Ying Gu, Xing-Xing Shi, Mao Le, Zheng Yin, Ming-Hua Zeng*

Cite this article: Chin. J. Struct. Chem., 2025, 44(7), 100602. DOI: 10.1016/j.cjsc.2025.100602

Publication date: July 1, 2025

Keywords: Open cubane cluster; ESI-MS; Correlation of crystal/solution/gas structural information; Synthesis and isolation; Assembly-disassembly-reassembly process

ABSTRACT

In mass spectrometry, fragments with a mass higher than the original molecular ion provide valuable insights into the molecular structure and can guide the assembly and disassembly processes for chemical synthesis. Here, we report such an example and following up by modifying the solvothermal reaction conditions (temperature and time) it was possible to isolate the high mass species in crystalline form. [Zn4L4Cl4] (Zn4L4, L = N-methylbenzimidazole-2-methanolate) has a boat-like Zn4O4 core but electrospray ionization mass spectrometry (ESI-MS) of the solution of its crystals shows higher mass peaks of Zn5L5, Zn5L6 and Zn6L6 species. Thus, both disassembly and reassembly are highly probable processes. Consequently, [Zn(HL)2Cl2] (Zn1, L = N-methylbenzimidazole-2-methanolate), [Zn4L6Cl2] (Zn4L6, L = N-methylbenzimidazole-2-methanolate) and [Zn6L6Cl4(CH3O)2] (Zn6L6, L = N-methylbenzimidazole-2-methanolate) were prepared. The results of multistage ESI-MS of their dissolved crystals led to a proposed mechanism of their formation in the gas phase as follows: [Zn3L4] through [ZnL] → [ZnL(HL)] → [Zn(HL)2] → [Zn2L] → [Zn2L2] → [Zn2L3]. The mechanism was derived in conjunction with Gibbs free energies calculated using DFT of the fragments observed in the ESI-MS of Zn4L4, Zn4L6 and Zn6L6. This work reveals the complex of chemical reactions, involving fragmentation and unexpected combination, under mass spectrometry conditions which allows one to synthesize the observed transients leading to mechanism of formation by correlation of solid-state/solution structural information.