Chiral crystal of a C2v-symmetric 1,3-diazaaulene derivative showing efficient optical second harmonic generation
KAUST DepartmentAdvanced Membranes and Porous Materials Research Center
Biological and Environmental Sciences and Engineering (BESE) Division
Physical Sciences and Engineering (PSE) Division
Chemical Science Program
Nanostructured Functional Materials (NFM) laboratory
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AbstractAchiral nonlinear optical (NLO) chromophores 1,3-diazaazulene derivatives, 2-(4â€-aminophenyl)-6-nitro-1,3-diazaazulene (APNA) and 2-(4â€-N,N-diphenylaminophenyl)-6-nitro-1,3-diazaazulene (DPAPNA), were synthesized with high yield. Despite the moderate static first hyperpolarizabilities (β0) for both APNA [(136 Â± 5) Ã - 10-30 esu] and DPAPNA [(263 Â± 20) Ã - 10-30 esu], only APNA crystal shows a powder efficiency of second harmonic generation (SHG) of 23 times that of urea. It is shown that the APNA crystallization driven cooperatively by the strong H-bonding network and the dipolar electrostatic interactions falls into the noncentrosymmetric P2 12121 space group, and that the helical supramolecular assembly is solely responsible for the efficient SHG response. To the contrary, the DPAPNA crystal with centrosymmetric P-1 space group is packed with antiparalleling dimmers, and is therefore completely SHG-inactive. 1,3-Diazaazulene derivatives are suggested to be potent building blocks for SHG-active chiral crystals, which are advantageous in high thermal stability, excellent near-infrared transparency and high degree of designing flexibility. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 Optical crystals based on 1,3-diazaazulene derivatives are reported as the first example of organic nonlinear optical crystal whose second harmonic generation activity is found to originate solely from the chirality of their helical supramolecular orientation. The strong H-bond network forming between adjacent choromophores is found to act cooperatively with dipolar electrostatic interactions in driving the chiral crystallization of this material. Copyright © 2011 Wiley Periodicals, Inc.
SponsorsGrants in aid from NSFC (Nos. 20933010 and 20911120087) and the National Basic Research Program of China (No. 2009CB220008) are acknowledged. The authors are grateful for the support from the Fundamental Research Funds for the Central Universities and the Research Funds of Renmin University of China (No. 10XNI007), and that from King Abdullah University of Science and Technology (KAUST No. 63652).