  We have witnessed a wide range of theoretical as well as experimental
investigations to envisage external stimuli induced changes in electronic,
optical, and magnetic properties in the metal organic complexes, while hybrid
perovskites have recently joined this exciting league of explorations. The
flexible organic linkers in such complexes are ideal for triggering not only
spin transitions but also a plethora of different responses under the influence
of external stimuli like pressure, temperature, and light. A diverse range of
applications particularly in the field of optoelectronics, spintronics, and
energy scavenging have been manifested. Hysteresis associated with light
induced transitions and spin-crossover governed by pressure and temperature are
promising phenomena for the design principles behind memory devices and optical
switches. Pressure induced optical properties tuning or piezochromism has also
emerged as one of the prominent areas in the field of hybrid perovskites. It is
thus imperative to have a clear understanding of how the tuning in electronic,
optical, and magnetic properties occur under various stimuli. Selectivity of
the stimulus could be influential behind the maximum efficiency in the field of
energy and optoelectronic research to determine in what future directions this
field could be driven from the perspective of futuristic material properties.
This review though primarily focuses on the theoretical aspects of
understanding the different mechanisms of the phenomena, does provide a unique
overview of the experimental literature too, such that relevant device
applications can be considered through a future roadmap of tuning paradigm of
external stimuli. It also provides an insight as to how energy and memory
storage may be combined by using the principles of spin transition in metal
organic complexes.
