Dual-emissive polydiphenylsilane nanocomposite: effect of N,N′- bis(4-hydroxysalicylidene)-1, 2-phenylenediamine-Zn complex Liviu Sacarescu*, Corneliu Cojocaru*, Rodinel Ardeleanu, Maria Fortuna, Gabriela Sacarescu and Mihaela Simionescu The fluorescence properties of polysilane can be strongly influenced by creating new excited states that involve electronic transitions and the relaxation to the ground state. This work presents the optical effects obtained by dop- ing a specially designed polydiphenylsilane copolymer with Zn complex of N,N′-bis(4-hydroxysalicylidene)-1,2- phenylenediamine. The nanocomposites have been prepared in solution by mixing the polymer with low amounts of Zn–salophen and using tetrahydrofuran as solvent. The ultraviolet–visible spectrum has shown the occurrence of an intermolecular charge transfer between polysilane and the metal complex. Photoluminescence studies have revealed an in- teresting dual emission profile of nanocomposite. The origin of this phenomenon has been evidenced by molecular model- ing and simulation of the electronic transitions. The modeling results have unveiled a new low-lying excited state due to intermolecular interactions. The thin films of nanocomposites have been drop-casted from solutions. The obtained films have been studied by Transmission Electron Microscopy (TEM)-Scanning Transmission Electron Microscopy (STEM)-Energy Disper- sive X-ray analysis (EDX) to gain information on the film-forming capacity and surface morphology. The results have revealed a high potential of such materials for fluorescence sensing applications. Copyright © 2015 John Wiley & Sons, Ltd. Keywords: polysilane; Zn–salophen; nanocomposite; emission spectra; molecular modeling INTRODUCTION Organometallic complexes represent a continuously growing field of research at both the fundamental and practical levels. In modern chemistry, exploitation of such structures gained new dimensions. Most of the high-tech applications rely on the metal complex (MC) capabilities to ensure and control a certain electrons “workflow” that dynamically sustains specific processes. [1–3] Insertion of metal atoms within organic frame- works leads to distortion of the ground electronic states with charge delocalization and re-mapping of the electrons density all over the molecule. [4–8] These effects could function in a very sensitive manner and could be driven in various ways ac- cording to needs. Besides catalytic properties of organometal- lic complexes, the new technological era focus the interest toward their exploitation in solar-harvesting devices, energy storage, photonics, nanoelectronics, and many others. [9–12] It is important to note that an almost constant research effort is dedicated to Schiff base complexes since interesting proper- ties in the field of nonlinear optics and magnetism have been discovered. [13–16] On the other hand, even an important num- ber of such structures are fluorescent; there are few reports where these structures are studied as materials for fluorescent sensors and electroluminescent devices. [17,18] Recently, Zn– Schiff base complexes have been reported to show strong electroluminescence and fluorescence. [19–21] Because these properties are affected by the chemical structure, intermolecu- lar interactions, and coordination number, [22–24] one can finely tune them by chemical adjustments of the building blocks or by specific processing methods. The mostly studied representatives of this class are MCs of N,N′-bis(salicylidene)-1,2-phenylenediamine (salophen). Re- cently, published works describe the properties of such struc- tures embedded in polymeric frameworks [25] with a strong emphasis on their catalytic activity and auto-assembling capa- bilities. These works reveal also aspects concerning the polarity of such structures that should be considered when the inten- tion is to build a hybrid organic–inorganic framework where all phases are perfectly miscible. Thus, high quantum efficien- cies in photoluminescent applications could be attained by blending MCs with polymers like in a host–guest system. The corresponding mechanism is related to the strong spin-orbit coupling induced by the metal centers. This enhances the in- tersystem crossing and mixing of the singlet and triplet states requested for radiative relaxation to occur. [26,27] On the other hand, non-miscibility of the phases is required to design materials for applications demanding dispersion of an * Correspondence to: Liviu Sacarescu and Corneliu Cojocaru, “Petru Poni” Insti- tute of Macromolecular Chemistry, Romanian Academy, Aleea Grigore Ghica Voda 41 A, 700487 Iasi, Romania. E-mail: livius@icmpp.ro; cojocaru.corneliu@icmpp.ro L. Sacarescu, C. Cojocaru, R. Ardeleanu, M. Fortuna, G. Sacarescu, M. Simionescu “Petru Poni” Institute of Macromolecular Chemistry, Romanian Academy, Aleea Grigore Ghica Voda 41 A, 700487, Iasi, Romania Research article Received: 07 May 2015, Revised: 18 June 2015, Accepted: 18 June 2015, Published online in Wiley Online Library: 19 July 2015 (wileyonlinelibrary.com) DOI: 10.1002/pat.3608 Polym. Adv. Technol. 2016, 27 115–124 Copyright © 2015 John Wiley & Sons, Ltd. 115