Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India.
J Chem Phys. 2012 Jan 7;136(1):014112. doi: 10.1063/1.3671946.
The symmetrized density matrix renormalization group method is used to study linear and nonlinear optical properties of free base porphine and metalloporphine. Long-range interacting model, namely, Pariser-Parr-Pople model is employed to capture the quantum many-body effect in these systems. The nonlinear optical coefficients are computed within the correction vector method. The computed singlet and triplet low-lying excited state energies and their charge densities are in excellent agreement with experimental as well as many other theoretical results. The rearrangement of the charge density at carbon and nitrogen sites, on excitation, is discussed. From our bond order calculation, we conclude that porphine is well described by the 18-annulenic structure in the ground state and the molecule expands upon excitation. We have modeled the regular metalloporphine by taking an effective electric field due to the metal ion and computed the excitation spectrum. Metalloporphines have D(4h) symmetry and hence have more degenerate excited states. The ground state of metalloporphines shows 20-annulenic structure, as the charge on the metal ion increases. The linear polarizability seems to increase with the charge initially and then saturates. The same trend is observed in third order polarizability coefficients.
运用对称化密度矩阵重整化群方法研究了自由碱基卟啉和金属卟啉的线性和非线性光学性质。采用长程相互作用模型，即 Pariser-Parr-Pople 模型来捕捉这些体系中的量子多体效应。在修正矢量方法中计算了非线性光学系数。计算得出的单线态和三线态低能激发态能量及其电荷密度与实验以及许多其他理论结果非常吻合。讨论了激发时碳原子和氮原子位置上电荷密度的重新排列。从我们的键序计算中，我们得出结论，卟啉在基态下很好地用 18-轮烯结构来描述，并且分子在激发后会膨胀。我们通过考虑金属离子的有效电场来模拟规则金属卟啉，并计算激发光谱。金属卟啉具有 D(4h)对称性，因此具有更多简并的激发态。随着金属离子上电荷的增加，金属卟啉的基态显示出 20-轮烯结构。线性极化率最初似乎随电荷增加而增加，然后饱和。三阶极化率系数也观察到了相同的趋势。
