In the last two decades, design and syntheses of coordination supramolecular compounds, which involve a great number of interactions and self-assembly of organic ligands with functional groups and metal ions with specific directionality, has produced appreciable progress within the field of supramolecular chemistry and crystal engineering [1–7]. Recently the self-assembly approach has become one of the most widely used techniques for the preparation of many functional materials, due to its potential to translate molecular building blocks into well-defined solid-state systems with relatively facile manner [8–10]. The variety of self-assembled structures relies largely on the presence of suitable metal ligand interactions and supramolecular contacts (hydrogen bonding and other weak interactions) . Until now, many single-, double-, triple- and higher-order stranded supramolecular polymers have been generated by a self-assembly process [12–16]. Nevertheless, it is still a huge challenge to reasonably construct the expected architectures with unique properties [17–19]. To the best of our knowledge, few papers are discussed the morphology controlling of compounds and checking out their changes. They have only studied on different compounds such as micro crystals , HA films on highly ordered nanotubular , a new asymmetric quaterthiophene , Mn(III) metalloporphyrins that contain size controlled amorphous and crystalline nano- and micro sized coordination polymer buy Bafetinib , diarylethene single crystal  and copper–zinc-10,15,20-tetra(4-pyridyl) porphyrin coordination polymer . In another interesting study, we looked at; they have demonstrated a comprehensive morphology evolution from the porphyrin derivative by droplet templating on a hydrophilic substrate by just changing the assembly temperature . But in this work we wish to report the first solid-state conversion of Pb(II) supramolecular polymers with 5-chloroquinolin-8-ol ligand with microrods morphology to nanorods and nanoparticles of it without any treatment in environmental conditions.
Results and discussion
In summary, for the first time, we observed the simultaneous conversion of a bulk micromaterial to its nanostructures without any treatment at environmental conditions. [Pb2(5-Clq-8-ol)2(OAc)2]n (1) is a one-dimensional pencil shaped supramolecular polymer as a result of weak secondary M⋯C interactions. It seems that during this conversion, some secondary M⋯C interactions were removed until this morphology change happens. Although conversion of bulk to nanostructures is very rare in other materials, existence of weak secondary interactions in supramolecular systems, become it possible. During this conversion different morphologies of 1 were obtained from the bulk and sonochemical prepared samples of 1 after three months. In the sonochemical prepared sample, amorphous nanoparticles and in the bulk sample of 1, crystalline nanorods were obtained. If the material is isotropic and has amorphous structure, it will tend to form spherical shape like nanoparticles.
The authors would like to acknowledge the financial support of University of Tehran for this research under grant number 01/1/389845.
Microbial proteases are commercially important enzymes in various biotechnology industries [1,2]. In developing environmentally benign chemical synthesis, the proteases are foreseen as pivotal enzyme as the protease in non-aqueous media offers various novel attributes as compare to traditional aqueous enzymatic transformation .
Various strategies have been employed to improve the economics of large scale fermentative production of microbial proteases, includes the isolation of high producing strains, optimization of the medium, utilization of inducers, and heterologous expression of genes [4–6]. Although, currently protease have occupied 60% market of total enzyme sale, the global protease market is ever-growing . Therefore, development of novel, highly efficient methods for protease production and bio-catalysis continues to be a subject of research interest.