Batagin-Neto Augusto, Bronze-Uhle Erika Soares, Graeff Carlos Frederico de Oliveira
Campus Experimental de Itapeva, UNESP - Univ Estadual Paulista, Rua Geraldo Alckmin 519, 18409-010, Itapeva, SP, Brazil.
Phys Chem Chem Phys. 2015 Mar 21;17(11):7264-74. doi: 10.1039/c4cp05256k.
Melanins represent an important class of natural pigments present in plants and animals that are currently considered to be promising materials for applications in optic and electronic devices. Despite their interesting properties, some of the basic features of melanins are not satisfactorily understood, including the origin of their intrinsic paramagnetism. A number of experiments have been performed to investigate the electron spin resonance (ESR) response of melanin derivatives, but until now, there has been no consensus regarding the real structure of the paramagnetic centers involved. In this work, we have employed electronic structure calculations to evaluate the ESR parameters of distinct melanin monomers and dimers in order to identify the possible structures associated with unpaired spins in this biopolymer. The g-factors and hyperfine constants of the cationic, anionic and radicalar structures were investigated. The results confirm the existence of at least two distinct paramagnetic centers in melanin structure, identifying the chemical species associated with them and their roles in electrical conductivity.
黑色素是动植物体内存在的一类重要天然色素，目前被认为是用于光学和电子设备的有前景的材料。尽管它们具有有趣的特性，但黑色素的一些基本特征尚未得到令人满意的理解，包括其固有顺磁性的起源。已经进行了许多实验来研究黑色素衍生物的电子自旋共振（ESR）响应，但到目前为止，对于所涉及的顺磁中心的真实结构尚未达成共识。在这项工作中，我们采用电子结构计算来评估不同黑色素单体和二聚体的ESR参数，以确定与这种生物聚合物中未配对自旋相关的可能结构。研究了阳离子、阴离子和自由基结构的g因子和超精细常数。结果证实了黑色素结构中至少存在两个不同的顺磁中心，确定了与之相关的化学物种及其在电导率中的作用。
