Infinite coordination polymers in which metal ions or metal clusters are connected by molecular building blocks consisting of organic molecules or organometallic complexes have received a great deal of attention due to their useful applications in gas storage, [1] catalysis, [2] optics, [3] recognition, and separation.[4] Rationalization of their chemical and physical properties from structural studies is of fundamental interest in the field of coordination polymer materials. Similarly, micro-and nanostructured materials are essential in many different areas, such as catalysis, [5] optics, [6] biosensing, [7] medical diagnostics, [8] and data storage, [9] and their size, shape, and composition are the key parameters that dictate chemical and physical properties.[10] Recently, a synthetic strategy for the preparation of micro-and nanoparticles made from infinite coordination polymers has been demonstrated by several groups.[11] This new class of materials promises to advance nanoparticle science into the realm of infinite coordination polymers, and thereby circumvent the nominal composition limitations generally ascribed to nanoparticles.Control of the composition of nanoparticles generated from functionally defined precursors is a promising research area due to the fundamental interest in materials that have practical applications in chemistry, biology, physics, and related interdisciplinary fields. Coordination polymer particles (CPPs) made from functional metalloligand building blocks have been shown to have a high degree of tailorability.[11a, b] The development and application of CPP materials requires an understanding of how the particles are formed, and the ability to control their size and shape. Herein we describe a solvothermal approach for the synthesis of CPPs made from transition-metal ions and metallosalen (salen = N,N'-bis(salicylidene)ethylenediamine) building blocks. We also describe an interesting nanoparticle wire-to-cube morphological transformation, and the utilization of this transformation process to control CPP formation.In a typical synthesis, fluorescent cubic nanoparticles were prepared by the following simple procedure (Scheme 1):carboxy-functionalized salen ligand N,N'-phenylenebis(salicylideneimine)dicarboxylic acid [12a] (1, 3 mg) was dissolved in DMSO (1 mL), and the solution was added to DMF (2 mL) containing two equivalents Zn(OAc) 2 . One equivalent of Zn 2+ coordinates to the salen pocket to give Zn-metalated salen (Zn-MS) [12] complex. The other Zn 2+ ion acts as a node that connects to the Zn-MS metalloligands through the carboxylate groups to form coordination polymer (Zn-MSZn); when one equivalent Zn 2+ is used, the coordination polymer does not form. The resulting solution was heated at 120 8C for 60 min. During this time, formation of particles was observed. The reaction mixture was cooled to room temperature, and the precipitate was collected by centrifugation and washed several times with DMSO and methanol. The resulting particles were found to be stable in organic so...