at the exception of the b - tcne structure that was taken in the 
 literature , the ground - state geometries 
 of all compounds were optimized at the ccsd level with a large atomic 
 basis set , typically def2-tzvpp ( see the si for cartesian coordinates ) . the optimizations 
 were performed with the gaussian09 program , imposing a tight convergence threshold on the forces 
 and using 10 and 10 a.u . the eom - ccsd and td - dft calculations were performed with the same 
 program , applying dunning s aug - cc - pvtz atomic 
 basis set , but for the coupled - cluster calculations on dmabn and b - tcne 
 that were modeled using the aug - cc - pvdz atomic basis 
 set for obvious computational reasons . the ccsd(t ) calculations in 
 the si were performed with gaussian09 as 
 well . the gw and bse 
 calculations used aug - cc - pvtz and have been achieved 
 with the fiesta package , applying the 
 coulomb - fitting resolution - of - identity ( ri - v ) technique . it is important 
 to stress that we used here the so - called evgw level ; 
 that is , we self - consistently converged the occupied / virtual gw energy levels while keeping the input dft eigenfunctions 
 frozen . we corrected at the gw level all valence 
 occupied dft levels and twice that amount of virtual levels . the bse 
 calculations were made with the  full  matrix ; that 
 is , we do not apply the tamm the starting dft eigenstates 
 were generated with nwchem using the 
 m06 and m06 - 2x hybrid functionals and 
 applying the xfine integration grid as well as 10 and 10 a.u .
developing ab initio 
 approaches able to provide accurate excited - state 
 energies at a reasonable computational cost is one of the biggest 
 challenges in theoretical chemistry . in that framework , the bethe 
 salpeter 
 equation approach , combined with the gw exchange - correlation 
 self - energy , which maintains the same scaling with system size as 
 td - dft , has recently been the focus of a rapidly increasing number 
 of applications in molecular chemistry . 
 using a recently proposed 
 set encompassing excitation energies of many kinds [ j. phys . 
 chem . 
 lett.2016 , 7 , 586591 ] , 
 we investigate here the performances of bse / gw . we 
 compare these results to caspt2 , eom - ccsd , and td - dft data and show 
 that bse / gw provides an accuracy comparable to the 
 two wave function methods . 
 it is particularly remarkable that the 
 bse / gw is equally efficient for valence , rydberg , 
 and charge - transfer excitations . 
 in contrast , it provides a poor description 
 of triplet excited states , for which eom - ccsd and caspt2 clearly outperform 
 bse / gw . this contribution therefore supports the 
 use of the bethe 
 salpeter approach for spin - conserving transitions .