Quantum Chemical Study of Structures, Electronic Spectrum, and Nonlinear Optical Properties of Gold−Pentacene Complexes

Abstract

Four isomers formed by a gold atom attached to a pentacene molecule were investigated by density functional theory due to their potential applications in molecular electronics. The aim of our study is to shed light on the bonding nature and interaction between gold and carbon, to estimate the influence of gold atoms on the electronic spectrum of the pentacene, and to predict second-order nonlinear optical (NLO) properties. The results show that the gold and carbon atom of systems 1 and 2 can form a covalent bond, which has σ single-bond character. However, there are strong donor-acceptor interactions between gold and carbon of systems 3 and 4. The influence of the number of benzene rings on the bonding nature or interactions is also discussed. Adding a gold atom to the pentacene obviously changes the transition nature of pentacene and results in an increase in possible transition, especially for systems 3 and 4. These systems possess moderate molecular second-order polarizabilities compared with the organometallic and organic complexes. The β value of system 4 is greater than that of system 1. Thus, subtle variations in the molecular architecture result in substantial enhancement of the second-order NLO response. In view of high transparency and the moderate β values, our studied systems could become a kind of potential second-order NLO material.

Theoretical investigation of structures, electronic spectra and nonlinear optical properties of gold-pentacene (Au2C22H14) complexes

“…According to Ref. [35], when only one Au atom is attached to C(3) or only one Au atom is attached to C(4), no distinct covalent bonds were observed in these two systems. However, when two Au atoms were attached to one pentacene molecule, the covalent bonds of all Au-C bonds are formed in all systems studied in this job.…”

“…[35], we know that adding one gold atom to the central benzene ring of the pentacene molecule (shown in Fig. 1) is the most stable (AuC 22 H 14 ).…”

“…Table 1. To be interesting, the bond length of Au-C in (AuC 22 H 14 ) is 2.169 Å [35], however, adding the second gold atoms to the pentacene molecule can abbreviate Au(1)-C(1) bond distance of (Au 2 C 22 H 14 ), except for System 4. Thus, these 7 systems are stable adsorption configuration due to improvement of Au(1)-C(1) bond.…”

“…This feature suggests these complexes may have large nonlinear optical responses. The structures and NLO of the systems formed by one gold atom and pentacene have been studied by our group [35] to the center C of a pentacene (AuC 22 H 14 ) is the most stable one with moderate molecular second-order polarizabilities. The charge transfer between Au and pentacene has great influences on the NLO.…”

Quantum chemical studies on tuning the second-order nonlinear optical molecular switching of triarylborane derivatives

“…Novel molecular materials with optimal nonlinear optical (NLO) properties are still in great demand because of their primary roles in applications in fields including optical communications and computation, optical switching and limiting, data storage and retrieval, and sensors [1][2][3][4]. Recently, triarylborane (TAB) and its derivatives have attracted increasing attention because of their strong photophysical properties, and have been making greater contributions in the fields of luminescence [5][6][7][8], optoelectronics (organic light-emitting diodes and electroluminescence (OLED/EL), nonlinear optical and two-photon absorption) [9][10][11][12], catalytic polymerization [13][14][15] and anion sensors [16][17][18], because their intriguing electronic structures come from the p  - conjugation through the vacant p-orbital on the boron atom (p(B)) [19,20].…”