Zoanthoxanthins and derivatives are rare cases of nitrogen-containing, polycyclic pigments discovered in colonial anthozoans of the family Zoanthidea in the 1970s. These compounds are characterised by intense fluorescence and acidochromism. However, many structural and photophysical aspects of these molecules remain unexplained. This investigation is the first attempt to provide a deeper understanding on the electronic and photopysical properties by means of quantum chemical methods. Two among the most diffused examples of parazoanthoxanthins have been chosen as a study case. The problem of the complex tautomerism these molecules undergo has been addressed, along with the protonation in acidic environment. The electrical properties and the topological features of the ground state have been investigated in details, revealing an environmental sensitive, quadrupolar nature of the investigated systems. A specific protocol has been designed to efficiently describe the excited electronic states in solution, which provided a good match with the experimental data. A particular attention was dedicated to explore the potential energy hypersurface of S₁, which revealed to possess one or two stable minima, dependently of the type of molecular system, the environmental conditions and the position of the protons. These fluorophores constitute a class of potentially promising molecular systems with tuneable photophysical properties.

zoanthoxanthins及其衍生物是在1970年代在Zoanthidea家族的殖民化花小动物中发现的含氮多环色素的罕见情况。这些化合物的特征在于强烈的荧光和酸致变色。但是，这些分子的许多结构和光物理方面仍无法解释。这项研究是首次尝试通过量子化学方法更深入地了解电子和光物理性质。在研究中选择了扩散最为广泛的副黄嘌呤实例中的两个。这些分子经历了复​​杂的互变异构问题，以及在酸性环境中的质子化。详细研究了基态的电学性质和拓扑特征，揭示了所研究系统的环境敏感性，四极性质。设计了一种特定的协议来有效地描述溶液中的激发电子态，这与实验数据非常吻合。特别要注意探索的势能超表面S ₁，根据分子系统的类型，环境条件和质子的位置，具有一个或两个稳定的最小值。这些荧光团构成了一类具有可调节光物理性质的潜在有前途的分子系统。