Linear and Nonlinear Optical Properties of Expanded Porphyrins: A DMRG Study

Abstract

We study absorption spectra and two photon absorption coefficient of expanded porphyrins (EPs) by the density matrix renormalization group (DMRG) technique. We employ the Pariser-Parr-Pople (PPP) Hamiltonian which includes long-range electron-electron interactions. We find that, in the 4n+2 EPs, there are two prominent low-lying one-photon excitations, while in 4n EPs, there is only one such excitation. We also find that 4n+2 EPs have large two-photon absorption cross sections compared to 4n EPs. The charge density rearrangement in the one-photon excited state is mostly at the pyrrole nitrogen site and at the meso carbon sites. In the two-photon states, the charge density rearrangement occurs mostly at the aza-ring sites. In the one-photon state, the C-C bond length in aza rings shows a tendency to become uniform. In the two-photon state, the bond distortions are on C-N bonds of the pyrrole ring and the adjoining C-C bonds which connect the pyrrole ring to the aza or meso carbon sites.

Nonlinear Optical Properties Tuning in Meso-Tetraphenylporphyrin Derivatives Substituted with Donor/Acceptor Groups in Picosecond and Nanosecond Regimes

“…Organic materials such as polymethine dyes [ 1 ], chromophores [ 2 ], phthalocyanines [ 3 ], porphyrins [ 4 ], and their related compounds [ 5 ] are target materials to study nonlinear optical (NLO) properties. The conjugated π-electron bonding networks in these molecules are the principal reason for their typical NLO properties [ 6 , 7 ].…”

An Overall Comprehension of Anti‐Aromatic Porphyrinoids Using 3D‐Graphical Chemical Shielding Description

“…As shown in Figure , when two opposite meso‐N atoms are replaced by two pyrrole units, the 18 π‐electron aromatic porphyrin will be changed into a 24 π‐electron anti‐aromatic porphyrinoid ( 14 ) [ 28 ] with the LLDP/IDR as high as (−10.5–−15.5 a.u. )/1307 a.u.…”

“…However, as the isomer of 14 / 15, the anti‐aromatic performance of 16 [ 28 ] is really bad. As can be found in Figures 10, if two opposite 2‐methylpyrroles are replaced by two pyridines, the in‐ring LLDP/IDR is immediately reduce from (−10.5–−15.5 a.u.…”

Correlated Electronic Properties of a Graphene Nanoflake: Coronene

“…Ab initio DMRG calculations for neutral systems employing molecular orbitals have bottlenecks since the calculation of two-electron integrals is computationally expensive, and consequently, these studies employ ∼50 active space orbitals [55]. On the other hand, DMRG calculations with localized orbitals have been successfully employed for π-conjugated systems with several hundred pz orbitals within the PPP Hamiltonian [53,56,57,58,59]. The ab initio study of arenes using the DMRG method has also revealed that fully-localized orbitals bring about faster convergence of energies compared to canonical Hartree–Fock orbitals or split-localized orbitals [55], making the localized description the picture of choice.…”