Two-phase Couette flow linear dichroism measurement of the shear-forced orientation of a palladium(II)-induced aggregate of thioether-derivatised subphthalocyanines at the toluene/glycerol interface

Formation of the Pd(II)-induced thioether-derivatised subphthalocyanine Subpc(SR)(6) ( R = Et (ethyl) or Bz (benzyl)) aggregate at the toluene/glycerol interface was investigated by means of a new in situ spectrophotometric method using two-phase Couette flow (TPCF). The shear-forced orientation of the aggregate of Subpc(SR)(6) - Pd(II) complexes formed at the toluene/glycerol interface was studied by their linear dichroism (LD) spectra. The H-aggregate of the Subpc(SEt)(6) - Pd(II) complex gave no LD signal, but the J-aggregate of the Subpc(SBz)(6) - Pd(II) complex clearly afforded LD spectra at a wide range of rotation speeds, suggesting a longer J-aggregate structure in the Subpc( SBz)(6) - Pd( II) system. The relaxation kinetics of the shear-forced orientation of the Pd( II) - Subpc( SBz)(6) aggregate were observed after stopping the rotation and analysing using a multi-exponential decay equation. By increasing the Subpc(SBz)(6) concentration in toluene, the fast relaxation fraction of 6.6 - 7.5 seconds decreased and the slow relaxation fraction of 292 - 322 seconds increased. The results obtained in this study demonstrate that the TPCF method is useful for studying the size distribution of aggregates formed at liquid/liquid interfaces.