The current project of the group has the title “Coordination chemistry on the nanoscale: Computational design of supramolecular building blocks capable of highly specific, orientation-dependent interactions.” The project is financed by CNCS-UEFISCDI (project number PN-III-P1-1.1-TE-2016-1279), and runs from May 2018 to April 2020.

With the advent of modern synthetic methods of nano- and mesoscale building blocks, it is now possible to encode complex self-assembling behaviour in relatively simple particles. However, the parameter space available for experimentalists is huge: one has to tune the building block anisotropy, interaction anisotropies, range, type etc. Computational methods can add valuable insight into the rational design of such building blocks. Coarse-grained modelling of anisotropic interactions can guide experiments into regions of the parameter space relevant to the desired target self-assembled structure. 

The present proposal aims to establish a new field for the self-assembly of nanoscale building blocks, through applying concepts from coordination chemistry into designs of nanoparticles, which will become capable of highly specific coordination to other nanoparticles. Although the concept of ‘colloidal molecules’ exists, experimental realizations are still in their infancy. In order to understand the behaviour of such building blocks, and to create the simplest possible models for them, we will be using and further developing state-of-the-art methods in energy landscape theory (global optimization within the rigid body framework, discrete path sampling and rigid body MD). 
In the first stage, we explore the minimal physics required for assembly of hollow cages formed by nanoscale analogues of MnL2n-type Goldberg polyhedra, which are experimentally realized by square planar coordinated transition metal complexes with nonlinear bidentate ligands. We propose that cages with the same symmetry can be obtained using a combination of excluded volume and Coulombic interactions, and we will investigate the dynamics of hollow shell formation and transition between competing structures. 

The second stage involves the design of novel anisotropic nanoparticles capable of tetrahedral, planar and linear coordination, giving rise to mesoscale structures analogous to hydrocarbons.

A previous project, financed by CNCS-UEFISCDI as well (project number PN-II-RU-TE-2014-4-1176) dealt with creating an ideal framework allowing for efficient modelling of the hierarchical self-assembly of anisotropic building blocks. The current project builds on this framework in order to investigate complex dynamics of model mesoscale systems that are feasible to create experimentally as well.

Summary of research activities during the first stage of the project
  • improving Monte-Carlo exploration for basin-hopping global optimization of colloidal particles
  • optimizing the evaluation of rigid-body potentials on GPUs
  • implementing the developed potentials into OPTIM
  • creating an algorithm for seeded global optimization

A detailed progress report can be downloaded from here.

Summary of research activities during the second stage of the project
  • global optimization of MnL2n-type shells
  • disconnectivity graphs for clusters of 24 and 30 central particles forming shells of different symmetries
  • preliminary MD confirmation of self-assembly of shells with exotic symmetries
  • long MD runs for macroions in explicit water
  • long MD runs for ss-CCMV capsid protein dimers and pentamers of dimers

A detailed progress report can be downloaded from here.