π–π-Induced aggregation and single-crystal fluorescence anisotropy of 5,6,10b-triazaacephenanthrylene

The influence of π–π overlap in centrosymmetric dimers on the aggregation type, single-crystal absorption and fluorescence anisotropy of the new heterocyclic system 5,6,10b-triazaacephenanthrylene is presented.


S1. Non-Covalent Interactions analysis
NCI analysis has been performed for the molecule of TAAP to confirm the existence of the geometrically predicted intramolecular interactions responsible for the decreased structural flexibility.
NCI (Non-Covalent Interactions) method utilizes the reduced gradient of electron density s(r) to visualize inter and intramolecular interactions.
To classify those interactions as favorable or unfavorable we multiply the electron density by the sign of second Hessian eigenvalue ( 2 ). Strong and attractive interactions are those with (r)>0 and 2 < 0, weak interactions (r)0 and 2  0 and strong and repulsive interactions are with (r)>0 and 2 > 0. Non-covalent interactions can be visualized as isosurfaces, where small red/blue disc-shaped regions represent strong repulsive/attractive interactions and broad, green and usually irregular surfaces refer to weak interactions. The analysis of interactions was performed via NCIPLOT program  Properties of the Bond Critical Points for the intermolecular interactions: (r)  charge density, Laplacian   2 (r) Rij  internuclear separations (Å), d1, d2  distance between BCPs and atom 1, 2 respectively (Å), V(r), G(r) and E(r) local kinetic, local potential and local energy density, respectively. All values except Rij and d1, d2 in a.u.  Ground state dipole moment for the molecule of TAAP has been calculated using DFT/B3LYP/6-311G**(2d,2p) and the result is visible on Figure S26.   Absorption spectra were recorded on a Hitachi U2900 spectrophotometer. Fluorescence emission spectra were measured with a fluorescence spectrophotometer Hitachi F7000. Excitation and emission slit widths were set at 5.0 nm. The excitation wavelength used for obtaining fluorescence spectra was 470 nm. From each recorded emission spectrum the solvent spectrum was subtracted and the resulting spectrum was corrected for nonlinearity in instrumental response.

S10. Determination of experimental permanent dipole moment
The measurement was performed in 1,4-dioxane saturated solution at 300 K. The dielectric constants of the solutions was measured by a Dipole Meter AGILENT E4980A using condenser cell 16452A.
The refractive indices was determined by the use of a Refractometer ATA60 RX5000CX Coubest. The density was measured by Densitometer Mettler Toledo 30PX. The reference liquid was 1,4-dioxane with 1 = 2.22.
The dipole moment of TAAP molecule in 1,4-dioxane saturated solution was determined according the following equation: Using CGS units, and extending to the frequency dependent response, the molecular polarizability is given by: where N is the molecular number density in cm 3 and is the polarizability in cm 3 . is related to the \excitation volume".
Then, the CM relation is: This equation is valid in principle only for cubic systems, but it's a good approximation to the dielectric function for isotropic systems. Note that optical absorption is related to 2 ≡ Im , the imaginary part of the dielectric function. When N . 1 the solid absorption energy  is markedly shifted from the absorption energy of the free molecule, as an effect of the collective response of all dipoles in the crystal.

S12.2. Molecular polarizability
We assume that the molecular polarizability as a superposition of Lorentian functions, with a small broadening ≪ 1: where the index  runs over electronic excitations of energy  and oscillator strength  . Note that  is not meant to reproduce vibronic and temperature effects. To take those into account, it is necessary to generate a gaussian of excitations centered around each electronic transition.