Hydrogen-bonded porous organic crystals are promising candidates for functional organic materials due to their easy construction and flexibility arising from reversible bond formation-dissociation. However, it still remains challenging to form porous materials with void spaces that are well-controlled in size, shape, and multiplicity because even well-designed porous frameworks often fail to generate pores within the crystal due to unexpected disruption of hydrogen bonding networks or interpenetration of the frameworks. Herein, we demonstrate that a series of C3-symmetric π-conjugated planar molecules (Tp, T12, T18, and Ex) with three 4,4'-dicarboxy-o-terphenyl moieties in their periphery can form robust hydrogen-bonded hexagonal networks (H-HexNets) with dual or triple pores and that the H-HexNets stack without interpenetration to yield a layered assembly of H-HexNet (LA-H-HexNet) with accessible volumes up to 59%. Specifically, LA-H-HexNets of Tp and T12 exhibit high crystallinity and permanent porosity after desolvation (activation): SABET = 788 and 557 m(2) g(-1), respectively, based on CO2 sorption at 195 K. We believe that the present design principle can be applied to construct a wide range of two-dimensional noncovalent organic frameworks (2D-nCOFs) and create a pathway to the development of a new class of highly porous functional materials.

Elastic organic crystals have attracted considerable attention as next‐generation flexible smart materials. However, the detailed information on both molecular packing change and macroscopic mechanical crystal deformations upon applied stress is still insufficient. Herein, we report that fluorescent single crystals of 9,10‐dibromoanthracene are elastically bendable and stretchable, which allows a detailed investigation of the deformation behavior. We clearly observed a Poisson effect for the crystal, where the short axes (b and c‐axes) of the crystal are contracted upon elongation along the long axis (a‐axis). Moreover, we found that the Poisson's ratios along the b‐axis and c‐axis are largely different. Theoretical molecular simulation suggests that the tilting motion of the anthracene may be responsible for the large deformation along the c‐axis. Spatially resolved photoluminescence (PL) measurement of the bent elastic crystals reveals that the PL spectra at the outer (elongated), central (neutral), and inner (contracted) sides are different from each other.

We have carried out large-scale computational quantum chemistry calculations on the K computer to obtain heats of formation for C60 and some higher fullerenes with the DSD-PBE-PBE/cc-pVQZ double-hybrid density functional theory method. Our best estimated values are 2520.0 ± 20.7 (C60), 2683.4 ± 17.7 (C70), 2862.0 ± 18.5 (C76), 2878.8 ± 13.3 (C78), 2946.4 ± 14.5 (C84), 3067.3 ± 15.4 (C90), 3156.6 ± 16.2 (C96), 3967.7 ± 33.4 (C180), 4364 (C240) and 5415 (C320) kJ mol(-1). In our assessment, we also find that the B3-PW91-D3BJ and BMK-D3(BJ) functionals perform reasonably well. Using the convergence behavior for the calculated per-atom heats of formation, we obtained the formula ΔfH per carbon = 722n(-0.72) + 5.2 kJ mol(-1) (n = the number of carbon atoms), which enables an estimation of ΔfH for higher fullerenes more generally. A slow convergence to the graphene limit is observed, which we attribute to the relatively small proportion of fullerene carbons that are in "low-strain" regions. We further propose that it would take tens, if not hundreds, of thousands of carbons for a fullerene to roughly approach the limit. Such a distinction may be a contributing factor to the discrete properties between the two types of nanomaterials. During the course of our study, we also observe a fairly reliable means for the theoretical calculation of heats of formation for medium-sized fullerenes. This involves the use of isodesmic-type reactions with fullerenes of similar sizes to provide a good balance of the chemistry and to minimize the use of accompanying species.

Many Divide-and-Conquer based approaches are being developed to overcome the high scaling problem of the ab initio methods. In this work, one such method, Molecular Tailoring Approach (MTA) has been interfaced with recently developed efficient Møller-Plesset second order perturbation theory (MP2) codes viz. IMS-MP2 and RI-MP2 to reap the advantage of both. An external driver script is developed for implementing MTA at the front-end and the MP2 codes at the back-end. The present version of the driver script is written only for a single point energy evaluation of a molecular system at a fixed geometry. The performance of these newly developed MTA-IMS-MP2 and MTA-RI-MP2 codes is extensively benchmarked for a variety of molecular systems vis-à-vis the corresponding actual runs. In addition to this, the performance of these programs is also critically compared with Fragment Molecular Orbital (FMO), another popular fragment-based method. It is observed that FMO2/2 is superior to FMO3/2 and MTA with respect to time advantage; however, the errors of FMO2 are much beyond chemical accuracy. However, FMO3/2 is a highly accurate method for biological systems but is unsuccessful in case of water clusters. MTA produces estimates with errors within 1 kcal/mol uniformly for all systems with reasonable time advantage. Analysis carried out employing various basis sets shows that FMO gives its optimum performance only for basis sets, which does not include diffuse functions. On the contrary, MTA performance is found to be similar for any basis set used.

An efficient parallel algorithm is developed for second-order Møller-Plesset perturbation theory with the resolution-of-identity approximation of twoelectron repulsion integrals (RI-MP2) to perform MP2 energy calculations of large molecules on distributed memory processors. Benchmark calculations are carried out for taxol (C 47 H 51 NO 14 ), valinomycin (C 54 H 90 N 6 O 18 ), and two-layer nanographene sheets (C 96 H 24 ) 2 , which show the high parallel efficiency of the developed algorithm.