Fig. 3: Self-assembly mechanism of the Rh424 square under kinetic control.
From: Pathway selection in the self-assembly of Rh4L4 coordination squares under kinetic control
a Three types of possible chain intermediates in the self-assembly of M4L4 square. Type I: MmLm+1, Type II: Mm+1Lm+1(dcb), Type III: Mm+2Lm+1(dcb)2. b Plots of the existence ratios of the substrates and products in the self-assembly of the Rh424 square from Rh(dcb)2 and 22– in CDCl3 at 298 K. [Rh]0 = [22–]0 = 0.86 mM. c Plots of the (〈n〉, 〈k〉) values in the n-k map of the Rh424 square (red filled circles). Green crosshairs indicate the (n, k) values of the chain intermediates. The three types of chain intermediates, Types I, II, and III, are plotted on each straight line. The brown number indicates m in each type of oligomer in a. The definitions of 〈n〉 and 〈k〉 values are shown in the main text (Eqs. 1 and 2). The data in (b) and (c) are shown as the average of the three runs of QASAP with standard errors. d Comparison of the existence ratio of the substrates and the products between QASAP (red) and NASAP (blue). e Comparison of the n-k plot between QASAP (red) and NASAP (blue). Both (d) and (e) indicate that the numerical simulation results reproduce the experimental counterparts well. f Dominant self-assembly pathways of the Rh424 square. Red arrows indicate the major self-assembly pathway. (a,b,c) indicates Rha2b(dcb)c. The numbers above the reaction arrows indicate the elementary reactions with high net reaction frequency listed in Supplementary Table 4. Longer Type II oligomers than (4,4,1), such as (5,5,1) and (6,6,1), are produced during the self-assembly, although they are not involved in the major self-assembly pathway (Supplementary Fig. 13). g Two possible pathways to produce triangle (3,3,0) from Type II intermediate (3,3,1) (left) and from Type II oligomers with more than three Rh2+ units (4+x, 4+x, 1) (x ≥ 0) (right). The green sphere indicates the leaving ligand(s) (dcb– or two molecules of CH3CN). h A plausible key structure in the triangular formation through associative ligand exchange process. Steric repulsion caused by ArCO2– (in green) in the cyclic intermediate and transition state of the triangular formation process would prevent the cyclization.
