Functionalized Tetrapodal Diazatriptycenes for Electrostatic Dipole Engineering in n‐Type Organic Thin Film Transistors

Abstract

A diazatriptycene‐based tetrapodal scaffold with thiol anchors enforces a nearly upright orientation of functional groups, introduced to its quinoxaline subunit, with respect to the substrate upon formation of self‐assembled monolayers (SAMs). Substitution with electron‐withdrawing fluorine and cyano as well as electron‐rich dimethylamino substituents allows tuning of the molecular dipole and, consequently, of the work function of gold over a range of 1.0 eV (from 3.9 to 4.9 eV). The properties of the SAMs are comprehensively investigated by infrared reflection absorption spectroscopy, near edge X‐ray absorption fine structure spectroscopy, and X‐ray photoelectron spectroscopy. As prototypical examples for the high potential of the presented SAMs in devices, organic thin‐film transistors are fabricated.

Porous Honeycomb Self-Assembled Monolayers: Tripodal Adsorption and Hidden Chirality of Carboxylate Anchored Triptycenes on Ag

“…Self-assembled monolayers (SAMs) are an important part of modern nanotechnology, with versatile applications ranging from corrosion protection and design of biointerfaces to lithography, nanofabrication, molecular electronics, organic electronics, and photovoltaics. − SAMs usually consist of rodlike molecules featuring an anchoring group, mediating the bonding to a specific substrate, a (functional) tail group, constituting the SAM–ambient interface, and a backbone, connecting both groups and building the SAM matrix. − Usually, each SAM-forming molecule comprises only a single docking group, but molecules with potentially dipodal, − tripodal, ,− and tetrapodal − building configurations (bearing a suitable number of anchoring groups) have been designed as well. Such systems, in particular, target at a better electronic coupling to the substrate, a better control of molecular orientation, a reliable assembly of bulky moieties to highly organized layers, and a control of the density of functional tail groups and specific receptors.…”

Triptycene-Based Tripodal Self-Assembled Monolayer on Indium Tin Oxide

“…The decoration of the ITO substrate with the Trip-CA monolayers results in just a small variation of the work function (0.14 eV range). Consequently, electrostatic engineering of interfaces with this type of molecular film will require the decoration of the triptycene framework with polar tail groups, such as −F, −CF 3 , −CN, −NH 2 , and −NMe 2 , , which will be the subject of future studies.…”

“…Self-assembled monolayers (SAMs) represent a key element of modern nanotechnology finding application in frontier technology areas such as organic/hybrid solar cells, organic field effect transistors, − electrochromic devices, sensors, , molecular electronics, − etc. SAMs are generally comprised of rod-like molecules bearing an anchoring group that binds to a specific substrate and a functional tail group constituting the SAM-ambient interface and, along with other parts of the molecules, redefining the physicochemical properties of the substrate. ,, Along with this most frequently used design concept involving a single anchoring group and monodentate bonding to the substrate, molecules with complex or multiple anchoring groups having potentially dipodal, tripodal, or tetrapodal bonding configurations were designed. − Such molecules bear the advantage of yielding more robust SAMs with improved electronic coupling to the substrate and flexible control over the density of the tail groups. − Among different multidentate configurations, molecular tripods, − including in particular triptycene derivatives that can form SAMs on a variety of metal substrates, − gain particular attention. The triptycene scaffold consists of three phenyl rings, which are disposed at a dihedral angle of 120° relative to each other.…”