Molecule Generation through Reasoning with Large Language Models

Congfeng Cao, Di Wu, Zhi Zhang, Jia-Hong Huang, Jelke Bloem, Khalil Sima’an


Abstract
Molecule generation is significant for its potential in scientific discovery and practical applications. Recent attempts often frame this task as a *translation* problem from molecular caption to structural representation, such as SMILES. This paper first examines the feasibility of modeling the task as a reasoning process with large language models (LLMs), generating higher-quality molecules through structural decomposition and recombination within curated Chain-of-Thought (CoT). We then introduce a workflow for curating accurate CoT data, incorporating both machine and expert verification. Lastly, we demonstrate that with a limited dataset of 4,213 curated samples, namely **MolCoT4K**, we elicit strong reasoning capabilities for molecule generation in open-source LLMs such as Qwen2.5-7B, achieving state-of-the-art exact match accuracy over strong open-source baselines (e.g., MolT5 and LlaSMol) as well as advanced commercial LLMs like GPT-4o. Moreover, the resulting model, **MolGeneration**, attains a Pass@16 exact match accuracy of 48.46%, highlighting its strong potential for real-world experimental applications when supported by a feasible external verifier or chemistry experts. Our analysis shows that the correctness of the CoT path is crucial, while reasoning ability primarily enhances accuracy in fine-grained molecule generation.
Anthology ID:
2026.findings-aacl.195
Volume:
Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
3862–3879
Language:
URL:
https://aclanthology.org/2026.findings-aacl.195/
DOI:
Bibkey:
Cite (ACL):
Congfeng Cao, Di Wu, Zhi Zhang, Jia-Hong Huang, Jelke Bloem, and Khalil Sima’an. 2026. Molecule Generation through Reasoning with Large Language Models. In Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026, pages 3862–3879, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Molecule Generation through Reasoning with Large Language Models (Cao et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-aacl.195.pdf