Cyclometalated complexes are an important class of (pre)catalysts in many reactions including hydride transfer. The ring size of such complexes could therefore be a relevant aspect to consider while modulating their catalytic activity. However, any correlation between the cyclometalating ring size and the catalytic activity should be drawn by careful assessment of the pertinent geometrical parameters, and overall electronic effects thereof. In this study, we investigated the vital role of key stereoelectronic functions of two classes of iridacyclic complexes-five-membered and six-membered cycles-in manupulating the catalytic efficiency in a model hydride-transfer reaction. Our investigation revealed that there exists an interesting multidimensional synergy among all the relevant stereoelectronic factors-yaw angle, bite angle, and the electronic properties of both the ligand and the metal center-that governs the hydride donor ability (hydricity) of the complexes during catalysis. Thus the six-membered chelate complexes with small yaw and large bite angles, strong donor ligand, and electron-rich metal were found to be better catalysts than their five-membered analogues. A frontier molecular orbital analysis supported the significant role of the above stereoelectronic synergistic effect associated with the chelate ring to control the hydride donor ability of the complexes.

Temperature is often not considered as ap recision stimulus for artificial chemical systems in contrast to the hostguest interactions related to many natural processes.Similarly, mimicking multi-state volatile memory operations using asingle molecular system with temperature as aprecision stimulus is highly laborious.H ere we demonstrate howamixture of iron(II) chloride and bipyridine can be used as ar eversible color-to-colorless thermochromic switch and logic operators. The generality of the approach was illustrated using Co II and Ni II salts that resulted in color-to-color transitions.DMSO gels of these systems,e xhibited reversible opaque-transparency switching. More importantly,o ptically readable multi-state volatile memory with temperature as aprecision input has been demonstrated. The stored data is volatile and is lost instantaneously upon withdrawal or changeo ft emperature.S imultaneous read-out at multiple wavelengths results in single-input/ multi-output sequential logic operations such as data accumulators (counters) leading to volatile memory states.The present system provides access to thermoresponsive materials wherein temperature can be used as aprecision stimulus.

Designing surface-confined molecular systems capable of expressing changes in functional properties as a result of slight variations in chemical structure under the influence of an external stimulus is of contemporary interest. In this context, we have designed three tetraterpyridine ligands with variations in their core architecture (phenyl vs tetraphenylethynyl vs bithiophene) to create spray-coated electrochromic assemblies of iron(II)-based metallosupramolecular polymer network films on transparent conducting oxide substrates. These assemblies exhibited molecular permeability and spectroelectrochemical properties that are in turn dictated by the ligand structure. Electrochromic films with high coloration efficiencies (up to 1050 cm 2 /C) and superior optical contrast (up to 76%) with a concomitant color-to-color redox transition were readily achieved. These functional switching elements were integrated into sandwich-type electrochromic cells (CE up to 641 cm 2 /C) that exhibited high contrast ratios of up to 56%, with attractive ON−OFF ratios, fast switching kinetics, and high operational stability. Every measurable spectroelectrochemical property of the films and devices is an associated function of the ligand structure that coordinates the same metal ion to different extents. While exhibiting a ligand-structure induced differential metal coordination leading to porosity and spectroelectrochemical diversification, these assemblies allow the creation of electrochromic patterns and images by a simple spray-coating technique.