z Materials Science inc. Nanomaterials & Polymers Salicylic Acid Appended Naphthalene Diimide Organic Linkers: ASystematic Investigation towards Electronic Aspects Anamika Kalita,* Samiran Upadhyaya, and Neelotpal Sen Sarma [a] A series of organic linkers (NDI-1, NDI-2, NDI-3) constructed from electron-deficient naphthalene diimide (NDI) ligand equipped with two terminal salicylic acid having carboxylic and hydroxyl functionality located at different positions provided NDI linkers as a structural platform with tunable properties is presented here. Evaluating the structure and functional relationship offered by prepared NDI organic linkers is a topic of interest related to the design of functionally active building blocks. In this study, synthesis and characterization of all the designed organic linkers were investigated and their photo- physical properties along with computational studies were performed to establish a correlation between structural design, self-assembly and intrinsic properties like electrical conductivity and so on. The hydrogen-bonding assisted conducting proper- ties of the linkers were presented which revealed the possible application of linkers as electro-active building blocks. 1. Introduction Self-assembly or self-organization to construct supramolecular architecture is a spontaneous association process of molecular components through non-covalent interactions such as hydro- gen-bonding, hydrophobic interactions, π-π stacking, van der Waals forces, electrostatic interactions, and so on. [1–5] Tunable structural diversity and modes of interaction among the functional molecule result in the formation of self-assembled structures. [6] Considerable interest in supramolecular self- assembly using various functional π-systems has grown in recent years. Molecular self-assemblies of small π-conjugated systems have attracted enormous research interest in light of their applications in optoelectronics, chemosensors, nanotech- nology, biomedicines and energy materials etc. [7–10] To constuct a controlled supramolecular architectures from a noncovalently associated π-conjugated system with variable functionality is still a challenging task. [11] Amongst different π-conjugated system identified, 1.4.5.8- Naphthalene Diimides (NDIs) are particularly promising material with potential application in numerous field. Preference of NDI core unlike others is due to its excellent inherent properties like planar conjugated structure, chemical robustness, electron- deficient and redox-active nature etc. These properties make NDI an ideal π-conjugated building block for fabrication of supra molecular architectures too. [12,13] While supramolecular design strategy is concern, self-assemblies of such π-conju- gated systems, attachment of amino acid/peptide fragments to organic NDI core is a hastily expanding area of modern research. [14–23] The high directional nature of hydrogen-bonding from the amino/peptide backbone along with the π-function- ality of the aromatic core can be simultaneously utilized to form a supramolecular self-assemblies [24] with promising molec- ular properties especially electronic behavior. The electro- active/conducting behavior of various organic linkers/building blocks were achieve through the self-assembly features of confined structures/functionalities. [25] In view of this, Ghosh et al. worked on a morphology-dependent gelation of naphthalene diimide molecules and reported a electrical conductivity value of the gel 10 6 Scm 1 and without gelation 10 8 Scm 1 . Again the same group has reported electrical conductivity of self-assembled carboxylic acid-appended naphthalene diimide derivatives 10 4 Scm 1 and 10 9 Scm 1 for the control compound. Rachana et al., demonstrated temper- ature dependent electrical conductivity of self-assembled linear alkyl chain-terminated NDI ranging from 10 6 Scm 1 to 10 5 Scm 1 . Banerjee et al. worked on an NDI xerogel and reported a conductivity value of 10 6 Scm 1 . [26–28,24] To construct self-assembled molecular architecture, utilizing new building blocks/linkers is still an appealing area that retains attention from the scientific community. The structures and functions of such systems are often tailored by the design of building blocks/organic linkers with specific lengths, geo- metries, and of course pendant functional groups. [29] The pendant functional groups mainly included in the organic linkers for acting as a coordinating unit involves carboxylate, hydroxyl, sulfonate, phosphonate, some N-containing groups like amide, imidazole, pyridine etc. [30] Among various functions, carboxylic acid bounded linkers/ligands have attracted attention [31] due to the formation ofself-assembled structure via hydrogen-bond interaction. It seems, the hydrogen-bonded carboxylic acids represent a particularly convenient topic of investigation for research community. They form cyclic dimers [a] Dr.A.Kalita,S.Upadhyaya,Dr.N.SenSarma Physical Sciences Division Institute of Advanced Study in Science and Technology, Paschim Boragaon, Guwahati-781035, Assam, India E-mail: anamik.kalita01@gmail.com Supporting information for this article is available on the WWW under https://doi.org/10.1002/slct.202002645 ChemistrySelect Full Papers doi.org/10.1002/slct.202002645 12672 ChemistrySelect 2020, 5, 12672–12678 © 2020 Wiley-VCH GmbH