Original article Red and yellow color aspects of compound 3-dicyclopropylmethylene- 5-dicyanomethylene-4-diphenylmethylenetetrahydrofuran-2-one: Chromism effect Abdullah G. Al-Sehemi a,b,c , Ahmad Irfan a, *, Abdullah M. Asiri d,e a Department of Chemistry, Faculty of Science, King Khalid University, Abha 61413, Saudi Arabia b Unit of Science and Technology, Faculty of Science, King Khalid University, Abha 61413, Saudi Arabia c Center of Excellence for Advanced Materials Research, King Khalid University, Abha 61413, Saudi Arabia d Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia e Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah 21589, Saudi Arabia 1. Introduction Previously [1] we shed light on the color change behavior of the title compound by tribochromism (color change due to mechanical friction). Now we introduce the crystallochromism (color change due to the change of crystal habit) and solvation chromism. Our recent quantum chemical study revealed that crystallochromism and solvation chromism would also be the major factors due to which the title compound, 3-dicyclopropylmethylene-5-dicyano- methylene-4-diphenylmethylenetetra-hydrofuran-2-one, gave yellow (1Y) and red (1R) crystals (Figs. 1 and S1, and Table S1 in Supporting information), while both give red solutions. Previously, we showed that in 1Y the diphenylmethylene groups are folded, i.e., one phenyl lies above a cyclopropyl group and the other above a cyano group, while in 1R the diphenylmethylene groups have a twisted orientation (one phenyl lies above a cyclopropyl group and the other below a cyano group) [1]. Moreover, we showed that the important calculated red and blue shifts correspond to the cases where the Al–N bonds are affected in the same direction, i.e., lengthening or shortening at the same time. The lengthening of Al–N bonds causes a red shift while shortening results in a blue shift [2]. 2. Computational details The ground state geometries were optimized at DFT/B3LYP/6- 31G** [3] level of theory with Gaussian09 package [4]. The frequency calculations were carried out at the same level of theory. The absorption spectra were computed by using TD-DFT/B3LYP/6- 31G** level of theory. 3. Results and discussions Significant differences in bond length (C7–C12), bond angles (C6–C5–C11 and C35–C38–C40) and dihedral angles have been observed between 1R and 1Y, see Table S1 (details can be found in Supporting information, labeling Fig. S2). In general, C5–C6, C8–C35 and C7–C12 bond lengths being lengthened in 1R, i.e., 0.016, 0.013 and 0.036 A ˚ , respectively, while O1–C9, C35–C38 and C12–C13 are being lengthened in 1Y, i.e., 0.013, 0.021, and 0.023 A ˚ , respectively. The following bond angles being increases in 1R; C6–C5–C11, C35– C38–C40 and C35–C38–C43, i.e., 2.66, 2.39 and 1.81 A ˚ , respectively, while C7–C12–C13 (1.79 A ˚ ) in 1Y. The noteworthy difference has been observed in the dihedral angles, e.g. in 1Y C1–C6–C5–C11, C8– C35–C36–C46, C7–C12–C13–C14 are 58, 1138, 208 more twisted Chinese Chemical Letters 25 (2014) 609–612 A R T I C L E I N F O Article history: Received 11 July 2013 Received in revised form 18 November 2013 Accepted 26 November 2013 Available online 13 January 2014 Keywords: Intermolecular interactions Crystallochromism Solvation chromism A B S T R A C T The title compound exists as yellow (1Y) and red (1R) crystals, but both gave red solutions. The intermolecular interactions between the CN parts of the crystals in 1Y are very weak. By the mechanical crushing as well as in solution 1Y again becomes red due to the absence of intermolecular interactions. We explain this color behavior by crystallochromism and solvation chromism. ß 2014 Ahmad Irfan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. * Corresponding author. E-mail address: irfaahmad@gmail.com (A. Irfan). Contents lists available at ScienceDirect Chinese Chemical Letters jo u rn al h om epag e: ww w.els evier.c o m/lo cat e/cc let 1001-8417/$ – see front matter ß 2014 Ahmad Irfan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. http://dx.doi.org/10.1016/j.cclet.2014.01.016