【作者】 王雪；

【导师】 丁益宏；

【作者基本信息】 吉林大学 ， 物理化学， 2023， 硕士

【摘要】 低氧化碳（C₃O₂）拥有长达150年的研究历史,在不同领域具有广泛的应用。作为经典的实验室碳源之一,其在有机合成化学中享有重要地位。在配位化学、大气化学、生命起源以及星际化学等方面都有重要的研究价值。结构决定性质是化学研究始终遵循的客观规律,一切深入研究都应该建立在一个准确结构的基础之上。然而C₃O₂分子气相结构的测定对实验来说始终是一个挑战,为此本文使用高精度计算方法重新计算了C₃O₂的气相几何,得到了比实验更为锐利的CCC弯曲角。其次关于C₃O₂异构化的研究十分有限,本文首次对其进行了系统的异构化研究,建立了单重态和三重态的全局反应势能面。最后基于全局反应势能面的建立,本文重新审视了星际重要反应模型O+C₃O,得到了全新的反应机理。详细的研究内容概况如下:（1）C₃O₂分子结构的金标准研究:一直以来,气相下的C₃O₂在结构和键合方面存有巨大的争议,关键在于CCC角的准确确定。在这项工作中,我们运用“金标准”方法,即CCSD（T）,重新审视了相当具有挑战性的CCC角度。让人非常惊讶的是,我们在CCSD（T）/aug-cc-pVnZ（n=T/Q/5）水平下计算出的C₃O₂结构具有一个比实验和计算中广泛接受的值（156°）更锐利的CCC角度（约148°）。（2）C₃O₂分子的异构化及解离稳定性研究:除了C₃O₂的星际存在问题以及气相下的电子结构问题一直处于激烈的争论之中,异构化方面,令人惊讶的是除链状以外的其他C₃O₂结构几乎没有被注意到。为了建立更多的C₃O₂化学反应模型,探索除链状以外的其他异构体存在的可能性,我们在CBS-QB3计算水平下建立了第一个极其全面的包含C₃O₂单重态和三重态反应通道的全局势能面,获得了23个全新异构体和62个全新过渡态。（3）氧原子消耗C₃O的量子化学机制研究:在CCSD（T）/CBS//CCSD/cc-p VTZ水平下的精确量子化学研究预测单重态氧原子（¹O）和三重态氧原子（³O）消除C₃O的反应是无能垒的,生成了天体物理上非常丰富的CO和三重态的CCO（³CCO）。反应的无能垒性质完全符合长期以来的猜想（O+C₃O一直被预期为无能垒）,但产物完全不同（文献认为产物是C₃+O₂）。本文的计算工作为理解天体物理中的碳循环和氧循环提供基础且有价值的理论信息。更多还原

【Abstract】 Carbon suboxide（C₃O₂）has a 150-year-long history of research and has a wide range of applications in different fields.As one of the classical laboratory carbon sources,it enjoys an important position in organic synthetic chemistry.It has important research value in coordination chemistry,atmospheric chemistry,the origin of life,and interstellar chemistry.It is an objective law that chemical research always follows that structure determines properties,and all in-depth studies should be based on accurate structure.However,the determination of the gas-phase structure of the C₃O₂ molecule is always a challenge for experiments.For this reason,in this paper,the gas-phase geometry of C₃O₂ is recalculated using a high-precision calculation method to obtain a sharper CCC bending angle than that of experiments.Secondly,due to the limited research on the isomerization of C₃O₂,this paper conducts a systematic study on the isomerization for the first time and establishes the global reaction potential energy surface of the singlet and triplet states.Finally,based on the establishment of the global potential energy surface,the important reaction model O+C₃O is re-examined in this paper,and a new reaction mechanism is obtained.Detailed research contents are summarized as follows:（1）“Gold standard”study of C₃O₂ molecule:C₃O₂ in gas-phase has still encountered significant debated in the structure and bonding.The key lies in the accurate determination of the CCC angle.In this work,we applied the“gold standard”method,i.e.,CCSD（T）,to revise the rather challengeable CCC angle.To our great surprise,our CCSD（T）/aug-cc-pVnZ（n=T/Q/5）calculations consistently predicted a much more acute CCC angle（ca.148°）than the widely accepted value 156°from experiment and computation.（2）Study on the isomerization and dissociation stability of C₃O₂ molecule:The electronic structure of C₃O₂ and the possibility of interstellar existence have continued to be in hot debate.In addition,it is surprising that other non-chain structure isomers are almost unnoticed.To establish more models of C₃O₂ chemical reaction and explore the possibility of other isomers except for chain-like structure,we have constructed the first extremely comprehensive global potential energy surface containing single and triplet state reaction channels of C₃O₂.At the CBS-QB3 computational level,we obtained 23 new isomers and 62 new transition states.（3）Accurate quantum chemical studies at the CCSD（T）/CBS//CCSD/cc-p VTZ level predicted the depletion of C₃O by both singlet and triplet O-atoms to be barrierless,leading to the astrophysically very abundant CO plus triplet CCO.The barrierless nature of the reaction fully complied with the long conjecture,whereas the product differed significantly.The computational work in this paper provides fundamental but valuable theoretical information for understanding the carbon and oxygen cycles in astrophysics.更多还原