Tracking the Transformation Process of a Pair of Zn(II) Coordination Clusters: Crystallography and Mass Spectrometry

Two zinc clusters Zn 4 (H 3 L) 4 (NO 3 ) 4 ⋅5H 2 O ( Zn 4 , H 4 L=(1,2‐bis(1H‐benzo[d]imidazol‐2‐yl)ethane‐1,2‐diol) and [Zn 5 (H 2 L′) 6 ](NO 3 ) 4 ]⋅8H 2 O⋅2CH 3 OH ( Zn 5 , H 3 L′=(1,2‐bis(benzo[d] imidazol‐2‐yl)‐ethenol) have been obtained by the reaction of Zn(NO 3 ) 2 ⋅6H 2 O with H 4 L at 80 °C or 140 °C under solvothermal condition. Powder X‐ray Diffraction (PXRD) of precipitate and Electrospray Ionization Mass Spectrometry (ESI‐MS) of reaction solution revealed the existence of transformation behavior from Zn 4 to Zn 5 by increasing the temperature from 80 °C to 140 °C, or directly heating Zn 4 at 140 °C via solvothermal reaction. Here we proposed a possible mechanism involves split process of Zn 4 and reassembly to form Zn 5 . ESI‐MS for single crystals revealed [Zn 4 (H 3 L) 4 −3H] + splits to [Zn(H 3 L)] + via [Zn 2 (H 3 L) 2 −H] + . Time dependent ESI‐MS of reaction solution revealed the [Zn(H 2 L′)] + →[Zn 2 (H 2 L′) 2 −H] + →[Zn 5 (H 2 L′) 6 −H] 3+ stepwise assembly. It also has been captured the in situ reaction mainly occurs in the step of [Zn(H 3 L)] + to [Zn(H 2 L′)] + .